Physiology of Acute and Chronic Inflammation, Health Implications, and the Role of Electrotherapy

Abstract Inflammation is the body’s response to injury, infection or exposure to toxic substances. Inflammation results from vascular, local immune and inflammatory cells responses to these injurious events. The cardinal signs of inflammation include redness, swelling, heat, pain, and loss of tissue function. Inflammation involves a variety of physiological changes and signalling cascade, which stimulate responses aimed at removing pathogens, debris and damaged cells, and promoting healing of the affected tissues. Inflammatory mediators cause sensitisation of nociceptors, increasing the perception of pain. Acute inflammation starts rapidly in response to harmful stimuli and may become severe, but normally the symptoms last for a relatively short period of time, usually few days. Generally, cellular and molecular events and interactions, occurring during acute inflammatory responses, minimise impending injury or infection. Such mitigation process contributes to restoring tissue homeostasis, and subsequently acute inflammation resolves. However, in some cases, inflammation can become chronic with detrimental effects. Uncontrolled inflammation can lead to the development of numerous chronic inflammatory diseases. Therefore, it is essential to identify and implement interventions for the management of inflammation. Electrotherapy is an approach that delivers exogenous electrical impulses to elicit favourable physiological changes, which bring about various health and fitness related benefits. Results from both human and animal studies suggest that electrotherapy can aid in the management of inflammation associated with different conditions.

Causes and Development of Acute Inflammation Inflammation is observed in living vascularised tissues, and occurs as a result of endogenous/exogenous harmful stimuli (Ehrman et al., 2003). The inflammatory response includes events at vascular and cellular level, especially immune cells. Inflammatory manifestations reflect the body’s response to tissue injury, invasion of pathogens, exposure to toxic compounds or irradiation (Medzhitov, 2010). Inflammation is a defence mechanism, with the aim of removing injurious stimuli, replace damaged cells and activate the healing process, which is critical for health (Ferrero-Miliani et al., 2007; Nathan & Ding, 2010). The inflammatory response involves various signalling pathways that regulate the level of inflammatory mediators in resident tissue cells and the activation of inflammatory cells, which are very important in the response to tissue injury or infection (Lawrence, 2009). The cardinal signs of inflammation include, rubor (redness) resulting from vasodilation of the vasculature in the affected tissue; calor (heat) due to local tissue hyperemia; tumor (swelling) caused by augmented vascular permeability and accumulation of fluid in the extravascular space; dolor (pain) due to the effect of oedema and inflammatory mediators, which activate nociceptors causing pain (Libby, 2007; Takeuchi & Akira, 2010). The loss of function in the inflamed tissue is mainly due to the development of pain and oedema (Flanagan, 1997; Kaspers et al., 2015).

Specifically, during acute inflammation there is a release of inflammatory mediators, such as bradykinin, histamine, prostaglandins and nitric oxide, which act on smooth muscles of blood vessels causing them to relax, leading to vasodilation. This reduces vascular resistance and increases blood flow, leading to redness and allowing more leucocytes and plasma proteins to reach the affected tissue. Moreover, the augmented permeability of the local vasculature facilitates immune cells and nutrients to pass out of the small blood vessels and reach the affected tissue (Guyton & Hall, 2011). The immune cells release leukotrienes and cytokines that are also inflammatory mediators, and the associated hyperaemia increases the hydrostatic pressure, while the elevated vascular permeability, due to augmented inter-epithelial gaps, causes plasma proteins and other substances to leak out, decreasing the colloid osmotic pressure within the vasculature. The increased hydrostatic pressure and the reduced colloid osmotic pressure, in presence of high microcirculation permeability, cause a greater amount of fluid to move out from the vasculature and accumulate in the interstitial compartment of the inflamed tissue, leading to the formation of oedema (Kaspers et al., 2015). The inflammatory mediators reach the hypothalamus via blood circulation, often leading to elevation in body temperature. The increased temperature enhances the innate immune defences by stimulating leukocytes to kill pathogens. Also, fever may inhibit the growth of many pathogens, helping to prevent infection (Evans et al., 2015). Besides, oedema increases the pressure in the traumatised region, activating the nociceptors, and also the inflammatory mediators irritate these nerve fibres, lowering their activation threshold, and pain develops as a consequence. The resulting hyperalgesia has a protective function, as by reducing mobility of the affected body region, helps prevent further damage (Guyton & Hall, 2011; Keele et al., 1984). There is also an increased number of immune cells in the inflamed tissue. These immune cells attack and remove pathogens, debris and damaged cells, through phagocytosis. Moreover, the activation of the repair mechanisms is associated with the inflammatory response (Chertov et al., 2000; Kaspers et al., 2015).

Essentially, acute inflammation is the body’s response to minimise impending injury or infection, and restore tissue homeostasis. Acute inflammation normally lasts for a relatively short period of time, usually few days, and then resolves. However, in some cases, inflammation can become chronic with detrimental consequences (Zou et al., 2006).

Chronic Inflammation and Development of Chronic Inflammatory Diseases Although intermittent increases in inflammation are crucial for survival during physical injury and infection, however, research has revealed that inflammation persisting over long periods of time has serious damaging effects (Furman et al., 2019). Chronic inflammation refers to slow, long-term inflammation lasting for prolonged periods of several months to years. Chronic inflammation is generally observed when acute inflammatory mechanisms fail to resolve tissue injury or eliminate pathogens (Lintermans et al., 2014). There are other factors that may cause chronic inflammation, such as autoimmune disorders and long-term exposure to irritants, including industrial chemicals or polluted air. Obesity, cigarette smoking, poor diet, elevated oxidative stress and hormone imbalance, can also contribute to chronic inflammation development (Furman et al., 2019). It should be considered that chronic inflammation is not a specific disease but a mechanistic process.

Most of the physiological changes that characterise acute inflammation, continue as the inflammation becomes chronic, including vasodilation, hyperaemia, increased vascular permeability and migration of neutrophils into the affected tissue through the capillary wall, in a process termed diapedesis. However, in chronic inflammation the composition of immune cells changes and mononuclear inflammatory cells, i.e. macrophages and lymphocytes infiltrate, with few granulocytes, i.e. neutrophils, present in the affected tissue (King, 2007). In addition to macrophages and lymphocytes, plasma cells also infiltrate in the affected tissue site. These different types of inflammatory cells, produce a variety of compounds, including growth factors, inflammatory cytokines and enzymes, which contribute to the progression of tissue damage and formation of granuloma and fibrosis. (Cutolo et al., 2019; Liu et al., 2017; Milenkovoc et al., 2019; Needham et al., 2019; Yousuf et al., 2019).

Thus, inflammation is the body‘s unique defence mechanism to maintain its integrity in response to injuries or infection. A normal inflammatory response is characterized by the temporally restricted upregulation of inflammatory activity, which occurs in the presence of a threat and that resolves once the threat has passed (Fullerton, 2016; Kotas & Medzhitov, 2015; Straub, 2017). However, if acute inflammation persists, it can become chronic, with detrimental effects on function and health. Important recent medical discoveries provided evidence that the immune system and inflammatory processes are involved in numerous health problems that dominate present-day morbidity and mortality worldwide (Bennett, 2018; Furman et al., 2017; Netea et al., 2017; Slavich, 2015).

Depending on the aetiology and tissue/organ affected, chronic inflammation may cause pain or progress silently. Chronic inflammation is associated with many chronic diseases, such as cardiovascular (Glezev & Buagh, 2014; Libby, 2012; Libby et al., 2010; Libby, 2002; Packard and Libby, 2008), bowel diseases (Cario & Podolsky, 2000; Strober et al., 2007), diabetes (Tsalamandris et al., 2019), neurodegenerative conditions (Fullerton & Gilroy, 2016), arthritis (Guo et al., 2018), fibromyalgia (Benlidayi, 2019) and cancer (Fernandes et al., 2015; Libby 2007). Chronic inflammatory diseases have been recognized as the most significant cause of death in the world today, with more than 50% of all deaths being attributable to inflammation-related diseases (Fullerton and Gilroy, 2016). Therefore, it is critical to identify and implement interventions for the management of excessive and chronic inflammation.

The Role of Electrotherapy for Treating Inflammation in Different Conditions The use of electricity in a medical context is no recent development, and it has been used as a therapeutic tool for over two millennia. Electrotherapy has evolved with the progress of science, and in the last several decades, we have witnessed an unparalleled growth in electronic technology and its application in medicine (Grimnes & Martinsen, 2000). Investigations into biology and electrophysiology revealed that bioelectric phenomena permeate living organisms, including humans, at different levels and are essential for the various physiological functions (Becker, 1974; Becker & Selden, 1985). Electrotherapy is a discipline based on evidence of the electric and electromagnetic phenomena, which arise in biological tissues, and the administration of exogenous electrical impulses for therapeutic purposes (Malmivuo & Plonsey, 1995; Watson, 2008). Electrotherapy comprises different modalities, including microcurrent stimulation (MCS), transcutaneous electrical nerve stimulation (TENS) and neuromuscular electrical stimulation (NMES). Each modality stimulates the body in a specific way causing favourable physiological changes, which bring about various health and wellbeing related benefits (Baboult et al., 2007; Bjordal et al., 2003; McMakin et al., 2005).

Findings from both human and animal studies suggest that electrotherapy may aid in the management of inflammation associated with different conditions. Erythema is a type of skin rash characterised by inflammation and redness, with varying degrees of severity. It usually occurs in response to a drug, excessive exposure to ultraviolet light, an infection or disease. Lee and co-workers (2011) evaluated the effects of MCS application for treating erythema and the associated inflammatory reactions induced by ultraviolet irradiation on the human skin. Two inflammatory reactions were induced with ultraviolet irradiation, which caused erythema in the lumbar region of each subject. One affected region of each subject was treated with MCS (experimental site) and the other was not treated (control site). The results demonstrated statistically significant changes in chromatic red and luminance, between the sites treated with MCS and the control sites. The improvements were greater in the sites treated with MCS (Lee et al., 2011) due to decreased levels of prostaglandins and other inflammatory mediators, thereby helping to reduce the inflammatory reactions (Lee et al., 2011; Kaur et al., 2011). Also, there was a statistically significant difference in wound contraction, which was greater in MCS treated sites compared to control sites.

Fibromyalgia, also known as fibromyalgia syndrome (FMS), is a long-term condition that affects muscles and soft tissue, and is very difficult to treat. Fibromyalgia is a potentially disabling chronic pain condition, and is the most frequent cause of chronic widespread pain (Kransler et al., 2002). Currently, there is no widely accepted efficacious treatment for this condition, and symptoms persist for years even with various approaches to therapy (Sprott, 2003). A study conducted by McMakin et al. (2005) evaluated the effects of MCS on pro-inflammatory cytokines and different pain biomarkers in patients with fibromyalgia associated with cervical trauma. The results showed a statistically significant reduction in pain and symptomatic relief from fibromyalgia following an average of eight MCS treatments. The median time to improvement was two months and the actuarial recovery curve reached 100% at 4.5 months. Moreover, interleukin-1, Interleukin-6 and substance P levels were all reduced from 330 to 80pg/ml, from 239 to 76pg/ml, and from 180 to 54pg/ml, respectively, in the first 90-minute treatment. Tumour necrosis factor-alpha (TNF-α) was also reduced from 305 to 78 pg/ml. During the same time period, both β-endorphin and cortisol increased from an average of 8.2 to 71.1 pg/ml, and 14.7 to 105.3 µg/ml, respectively. These improvements in pro-inflammatory cytokines and pain biomarkers were statistically significant.

Lung cancer patients exhibit various immune abnormalities, including cellular immune dysfunction, alterations in cytokines, microcirculatory disturbance and antigen presentation defects (Dasanu et al., 2012; Micheli et al., 2012). The intervention in patients with lung cancer usually involves surgical removal of the tumour, with a concomitant lymphadenectomy. The immune abnormalities are exacerbated by postoperative pain and surgical trauma, which may predispose patients to septic complications, multiple organ dysfunction, tumour spread or metastases, and mortality (Boboxea et al., 2012; Leaver et al., 2000). Therefore, it is critical to identify and implement strategies, which are able to attenuate perioperative immune dysfunction in lung cancer patients. The activation and differentiation of T lymphocytes is required for anti-infection and anti-tumour immune responses (Ren et al., 2010). Moreover, an imbalance in the relative levels of the various T-helper (Th) cells, including Th1, Th2 and Th17 cells, and regulatory T (Treg) cells, has been associated with immunological disturbances (Dai et al., 2013). A three arm randomised controlled trial (RCT) evaluated the effects of transcutaneous acupoints electrical stimulation (TAES) on Th1, Th2, Th17 and Treg cells, and the expression levels of associated cytokines and transcription factors, following thoracotomy of patients with lung cancer (Wu et al., 2016). TAES is a form of electrotherapy in which specifically chosen sites of acupuncture, termed acupoints, are stimulated for therapeutic benefits. Patients diagnosed with lung cancer who accepted thoracotomy were included in the study. Patients were randomized equally into 3 groups, 1) thoracotomy; 2) thoracotomy and sham TAES; and 3) thoracotomy and TAES groups. Group 3 received TAES at specific acupoints for 30 minutes prior to incision, and at 20, 44, 68, 92 and 116 hours following surgery. Group 2 received identical electrical stimulation to group 3, however, TAES was performed at sham acupoints. The results showed that TAES administration, in thoracic surgical patients with lung cancer, increased the percentage of Th1 and Th17 cells, the protein expression levels of interleukin-2 (IL-2), interferon-γ, the mRNA expression levels of T-bet and RAR-related orphan receptor-γt, and decreased the percentage of Th2 cells, IL-10 protein expression levels, and GATA binding protein 3 mRNA expression levels. Also, TAES alleviated postoperative pain and reduced analgesics medications requirements, nausea, vomiting and infection. The authors concluded that TAES was able to partially attenuate the postoperative immune depression of patients with lung cancer, by regulating the balance of Th1, Th2, Th17 and Treg cells, and the expression levels of related cytokines and transcription factors. Thus, TAES can be considered a promising strategy for the treatment of postoperative immune dysfunction in patients with lung cancer.

Surgical procedures elicit a physiological inflammatory host response, which comprises an intricate combination of immunological, metabolic, hemodynamic and hormonal signals that are designed to be protective and create a physiological milieu for promoting healing and recovery. An inflammatory response after surgery is essential for the healing process, however, too much inflammation can have adverse effects and increases significantly the recovery time. Regardless if the wound results from surgery or trauma, managing inflammation is critical, as in some cases wounds do not progress to normal healing with formation of a final mature scar, but to a continuing inflammatory process, which can progress to chronic wounds (Rosique et al., 2015). A prospective randomized sham-control trial (Chi et al., 2019) evaluated the efficacy of TEAS in improving recovery in a group of elderly patients receiving knee surgery under epidural anaesthesia. Patients were divided into two groups, the experimental group received TEAS treatment at specific acupoints, and the control group received sham treatment. Patients were treated for 30 minutes prior to the epidural anaesthesia and postoperative day 1 and 2, and biomarkers level of stress and inflammatory responses were assessed. The results showed that perioperative TEAS application is able to reduce surgical inflammation and perioperative stress response, facilitating postoperative recovery of elderly patients, especially at the early stage after surgery.

An RTC, carried out by Fiorelli et al. (2012), evaluated the effectiveness of TENS on post-thoracotomy pain, and assessed cytokines and pain levels, respiratory function and analgesics medication requirements. Patients who underwent standard posterolateral thoracotomy for resectable lung cancer, were included in the study and randomized into two groups, the experimental and placebo group, respectively. The experimental group received postoperatively TENS therapy for 5 days. In both groups serum cytokines (IL-6, IL-10, TNF-α) were measured before surgery and at 6, 12, 24, 48, 72, 96 and 120 postoperative hours. Also, pain score and respiratory function were assessed, and the total intake of analgesics medication given during the postoperative period of 5 days was recorded. The results demonstrated that Serum IL-6, IL-10 and TNF-α levels and pain in TENS group were significantly lower compared to placebo. Also, in the TENS group respiratory function improved and analgesics medication requirements decreased significantly compared to placebo.

Depression is a common and serious condition that causes low mood, feelings of sadness and loss of interest in activities. If untreated, depression can lead to a variety of emotional and physical problems, affecting daily life. Increased inflammatory response and an imbalance between T-helper (Th) 1 and 2 functions have been implicated in major depression (Song et al., 2009). An RCT evaluated the relationship between pro- and anti-inflammatory cytokines, and between Th1 and Th2 produced cytokines in depressed patients, and assessed and compared the effect of treatments with electroacupuncture (EA) and fluoxetine on these cytokines (Song et al., 2009). EA is an approach that combines electrotherapy and acupuncture principles. In this integrated approach, the electrical impulses are delivered to specific acupoints, by inserting acupuncture needles, for therapeutic benefits (Li & Wang, 2013). Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) drug, which is prescribed as an antidepressant. Outpatients with major depressive disorder were included in the study, and were treated for 6 weeks with EA, fluoxetine or placebo. A group of volunteers served as control. Hamilton Depression Rating Scale and Clinical Global Impression were used to assess the severity of the condition and the therapeutic effects, and serum cytokines concentrations were measured. The findings showed increased pro-inflammatory cytokine interleukin -1 β (IL-1 β) and decreased anti-inflammatory cytokine IL-10 in depressed patients. Also, Th1 produced pro-inflammatory cytokines, TNF-α and interferon-γ (IFN-γ) were decreased, while Th2 produced cytokine IL-4 and the ratio of IFN/IL-4 were increased significantly in depressed patients. Both EA and fluoxetine treatments, but not the placebo, reduced IL-1β concentrations in responders. However, only EA attenuated TNF-α concentration and IFN-γ /IL-4 ratio towards the control level. The authors concluded that in depressed patients there is an imbalance between the pro- and anti-inflammatory cytokines (IL-1 and IL-10), and between Th1 and Th2 cytokines (IFN-γ or TNF-α and IL-4), and that both EA and fluoxetine had an anti-inflammatory effect by reducing IL-1 β. Furthermore, EA treatment also restored the balance between Th1 and Th2 systems by increasing TNF-α and decreasing IL-4.

Rheumatoid arthritis is the most commonly diagnosed inflammatory arthritis, which typically affects women and elderly people. Rheumatoid arthritis is characterised by persistent synovitis, systemic inflammation, and autoantibodies. Uncontrolled active rheumatoid arthritis causes joint damage, disability, decreased quality of life, cardiovascular complications and other comorbidities. Reducing synovitis and systemic inflammation and improving function, are key objectives of rheumatoid arthritis therapy (Scott et al., 2010). An RCT, conducted by Ouyang and colleagues (2010), assessed the effects of EA on rheumatoid arthritis. Patients with rheumatoid arthritis were randomly divided into an EA group and a simple acupuncture group. Patients received either EA or simple acupuncture at selected acupoints. All patients were treated once every other day, for 20 days as one course. After 3 courses, changes of interleukins in peripheral blood and joint fluid of patients were assessed. The results demonstrated that both EA and simple acupuncture had a significant effect on IL-1, IL-4, IL-6 and IL-10 in peripheral blood and joint fluid of patients. However, following EA, the improvements in IL-1 and IL10 in peripheral blood and joint fluid, as well as IL4 in joint fluid were significantly greater than those of simple acupuncture. While, changes in IL-6 and IL-10 were almost the same after both treatments. The authors concluded that EA can effectively decrease the pro-inflammatory cytokines of IL-1 and IL-6 and increase the inhibition cytokines of IL-4 and IL-10, impacting on occurrence and progression of rheumatoid arthritis. In a subsequent RTC, Ouyang et al. (2011) evaluated the effect of EA on TNF-α and vascular endothelial growth factor (VEGF) in peripheral blood and joint synovial fluid in patients with rheumatoid arthritis. The patients included in the study were randomly divided into two groups, and treated with either EA or simple needling (SN), at selected acupoints. The treatments were administered every other day, 10 times as a course, and each patient received a total of 3 courses of treatment. The findings showed that blood and synovial levels of TNF-α and VEGF were reduced significantly after treatment in both groups. The lowering (absolute value and difference value) of TNF-α as well as the absolute value of VEGF, either in blood or in synovial fluid, were similar in the two groups. However, the lowering of VEGF after treatment was significantly greater in the EA group, compared to the SN group. The authors concluded that EA could effectively lower the levels of TNF-α and VEGF in peripheral blood and joint synovial fluid, impacting on incidence and development of rheumatoid arthritis, and enhancing the therapeutic effectiveness.

A number of animal model studies provided further evidence that electrotherapy is an important tool for the management of inflammation. Demir et al. (2004) conducted an animal study and reported that MCS and laser treatment have beneficial effects during the inflammatory, proliferation, and maturation phases of a wound. However, MCS has more beneficial effects during the inflammatory phase in some parameters, compared to laser treatment. The authors concluded that both MCS and laser treatment can be used successfully in decubitus ulcers and chronic wounds, in combination with conventional therapies such as daily care and debridement of wounds. The results of an RCT (Ainsworth et al., 2006) showed that either low or high frequency TENS applied to the gastrocnemius muscle of rodents, ipsilateral to the site of inflammation significantly reversed mechanical hyperalgesia, both ipsilateral and contralateral to the site of inflammation. Moreover, low or high frequency TENS applied to the gastrocnemius muscle contralateral to the site of inflammation also reduced mechanical hyperalgesia significantly, both ipsilateral and contralateral to the site of inflammation. Another animal study, carried out by Wang and colleagues (2014), showed that EA application elicits long-term antinociception, associated with peripheral opioid peptides. Also, the treatment altered the cytokine profile towards an anti-inflammatory pattern and augmented IFN-γ and the chemokine CXCL10 (IP-10: interferon gamma-inducible protein) and mRNA expression with concomitant increased numbers of opioid peptide-containing CXCR3+ macrophages. Sato and co-workers (2020), conducted an animal model study and compared the effects of TENS, manual acupuncture (MA), and spinal cord stimulation (SCS) on neuropathic, inflammatory, and non-inflammatory pain models. The results demonstrated that MA was only effective in the neuropathic and inflammatory models, while TENS and SCS were effective in all 3 models.

Considerations and Conclusion The number of non-communicable diseases is increasing at an alarming rate worldwide, and many of them are linked to inflammation. Environmental pollution, toxins, obesity, unbalanced diet, cigarette smoking and elevated oxidative stress, are factors that contribute to the development of inflammation. Usually, the extent and effects of inflammation vary with the cause of the injury and the ability of the body to repair and overcome the damage. There is now consensus in the scientific community that uncontrolled inflammation can lead to the development of numerous inflammatory diseases. Each inflammatory condition necessitates specific interventions for the management of inflammation. There is evidence suggesting that electrotherapy is efficacious in controlling inflammation associated with different conditions, such as rheumatoid arthritis, fibromyalgia and erythema. Also, electrotherapy application improves surgical inflammation and perioperative stress response, ameliorates the balance between pro and anti-inflammatory cytokines in depressed patients, promotes wound healing and reduces pain and pharmacological analgesics requirements. Electrotherapy is versatile and has been applied as stand-alone therapy, as well as in combination with other treatments. This therapeutic tool is almost side effects free and easy to apply, and can be incorporated in standard interventions for the prevention and treatment of acute inflammation and various inflammatory conditions.

References

1. Ainsworth L, Budelier K, Monica Clinesmith M. et al. Transcutaneous electrical nerve stimulation (TENS) reduces chronic hyperalgesia induced by muscle inflammation. Pain, 2006, 120, 182–187

2. Babault, N., Cometti, G., Bernardin, M., Pousson, M., Chatard, J.C. Effects of electromyostimulation training on muscle strength and power of elite rugby players. J Strength Cond Res. 2007, 21(2):431-7.

3. Becker R O, and Selden G. The Body Electric, New York: William Morrow & Co., 1985.

4. Becker, R. O. The significance of bioelectric potentials. Bioelectrochemistry and Bioenergetics, 1974 1:187-199.

5. Bennett JM, Reeves G, Billman GE, Sturmberg JP Inflammation–nature’s way to efficiently respond to all types of challenges: implications for understanding and managing “the epidemic” of chronic diseases. Front. Med, 2018, 5, 316.

6. Benlidayi IL. Role of inflammation in the pathogenesis and treatment of fibromyalgia. Rheumatol Int. 2019 May;39(5):781-791.

7. Bjordal JM, Johnson MI, Ljunggreen AE. Transcutaneous electrical nerve stimulation (TENS) can reduce postoperative analgesic consumption: a meta-analysis with assessment of optimal treatment parameters for postoperative pain. Eur J Pain. 2003; 7:181–188.

8. Bobocea AC, Trandafir B, Bolca C, Cordoş I. Minimally invasive surgery in cancer. Histopathology. Chirurgia (Bucur) 2012;107:154–157.

9. Cario E, Podolsky DK. Differential Alteration in Intestinal Epithelial Cell Expression of Toll-Like Receptor 3 (TLR3) and TLR4 in Inflammatory Bowel Disease. Infection Immunity. 2000; 68:7010–7017.

10. Chertov O, Yang D, Howard O, Oppenheim JJ. Leukocyte granule proteins mobilize innate host defenses and adaptive immune responses. Immunol Rev. 2000; 177:68–78.

11. Chi YL, Zhang WL, Yang F, et al. Transcutaneous Electrical Acupoint Stimulation for Improving Postoperative Recovery, Reducing Stress and Inflammatory Responses in Elderly Patient Undergoing Knee Surgery. Am J od Chin Med. 2019;47(7):1445-1458. doi: 10.1142/S0192415X19500745.

12. Cutolo M, Soldano S, Smith V. Pathophysiology of systemic sclerosis: current understanding and new insights. Expert Rev Clin Immunol. 2019 Jul;15(7):753-764.

13. Dasanu CA, Sethi N, Ahmed N. Immune alterations and emerging immunotherapeutic approaches in lung cancer. Expert Opin Biol Ther. 2012;12:923–937. doi: 10.1517/14712598.2012.685715.

14. Dai H, Sun T, Liu Z, Zhang J, Zhou M. The imbalance between regulatory and IL-17-secreting CD4+T cells in multiple-trauma rat. Injury. 2013;44:1521–1527. doi: 10.1016/j.injury.2013.03.015

15. Demir H, Balay H, Kirnap M. A comparative study of the effects of electrical stimulation and laser treatment on experimental wound healing in rats, Journal of Rehabilitation Research & Development. 2004, Volume 41, Number 2, Pages 147–154

16. Ehrman JK, Gordon PM, Visich PS, Keteyian SJ. Clinical Exercise Physiology. Human Kinetics Piblishers inc. 2003.

17. Evans SS, Repasky EA, Fisher DT. Fever and the thermal regulation of immunity: the immune system feels the heat. Nat Rev Immunol. 2015; 15(6): 335–349. doi:10.1038/nri3843.

18. Fernandes JV, Olivera Corbucci NR, Nunes Jatoba CA et al., The role of the mediators of inflammation in cancer development. Pathol Oncol Res, 2015 Jul;21(3):527-34.

19. Ferrero-Miliani L, Nielsen O, Andersen P, Girardin S. Chronic inflammation: importance of NOD2 and NALP3 in interleukin-1β generation. Clin Exp Immunol. 2007; 147:227–235.

20. Fiorelli A, Morgillo F, Milione R. et al. Control of post-thoracotomy pain by transcutaneous electrical nerve stimulation: effect on serum cytokine levels, visual analogue scale, pulmonary function and medication. Eur J Cardiothorac Surg. 2012 Apr;41(4):861-8; discussion 868.

21. Flanagan, M. Wound Management. Edinburgh: Churchill Livingstone, 1997.

22. Fullerton JN & Gilroy DW Resolution of inflammation: a new therapeutic frontier. Nat. Rev. Drug Discov, 2016, 15, 551–567.

23. Furman D, Campisi J, Verdin E, et al., Chronic inflammation in the etiology of disease across the life span. Nat Med. 2019, 25(12): 1822-1832.

24. Furman D, Chang J, Lartigue L, et al. Expression of specific inflammasome gene modules stratifies older individuals into two extreme clinical and immunological states. Nat. Med 23, 174–184 (2017).

25. Glezeva N, Baugh JA. Role of inflammation in the pathogenesis of heart failure with preserved ejection fraction and its potential as a therapeutic target. Heart Fail Rev. 2014; 19:681–694.

26. Grimnes S, Martinsen OG. Bioimpedance & Bioelectricity Basics. San Diego, CA: Academic Press, 2000.

27. Guo Q, Wang Y , Dan Xu D, et al., Rheumatoid arthritis: pathological mechanisms and modern pharmacologic therapies. Bone Research. 2018; 6: 15. doi: 10.1038/s41413-018-0016-9

28. Guyton, C. and Hall, J. 2011. Textbook of Medical Physiology, Twelfth edition, Elsevier. Kaspers DL, Hauser SL, Jameson JL, et al., Harrison’s Principles of internal medicine. New York: McGraw-Hill Companies. 19th ed; 2015.

29. Kaur S, Lyte P, Garay M, Liebel F, Sun Y, Liu JC, Southall MD: Galvanic zinc-copper microparticles produce electrical stimulation that reduces the inflammatory and immune responses in skin. Arch Dermatol Res 2011, 303:551–562.

30. Keele CA, Nail E, Joels N. Samoson wright’s Applied Physiology. Thirteen Edition, Oxford Medical Publications, 1984.

31. King TC. Inflammation, Inflammatory Mediators, and Immune-Mediated Disease. Elsevier’s integrated physiology, 2007, Pages 21-57.

32. Kransler, J.D., Gendreau, J.F., Rao, S.G. The psychopharmacology of fibromyalgia: a drug development perspective. Psychopharmacology Bulletin. 2002, 36 (1),165-213.

33. Kotas ME, Medzhitov R Homeostasis, inflammation, and disease susceptibility. Cell, 2015, 160, 816–827.

34. Lawrence T. The Nuclear Factor NF-κB Pathway in Inflammation. CSH Perspect Biol. 2009; https://doi. org/10.1101/cshperspect.a001651.

35. Leaver HA, Craig SR, Yap PL, Walker WS. Lymphocyte responses following open and minimally invasive thoracic surgery. Eur J Clin Invest. 2000;30:230–238. doi: 10.1046/j.1365-2362.2000.00622.x.

36. Lee JW, Yoon SW, Kim TH, Park SJ. The Effects of Microcurrent (MCS) On Inflammatory Reactions Induced by Ultraviolet Irradiation. Journal of Physical Therapy Science. 2011, 23, 693-696.

37. Li X, Wang Q. Acupuncture Therapy for Stroke Patients. International Review of Neurobiology. 2013, 111, 2013, 159-179.

38. Libby P. History of Discovery: Inflammation in Atherosclerosis. Arteriosclerosis Thrombosis Vascular Biology. 2012; 32:2045–2051.

39. Libby P. Atherosclerosis in Inflammation. Nature. 2002; 420:868–874.

40. Libby P, Okamoto Y, Rocha VZ, Folco E. Inflammation in atherosclerosis: transition from theory to practice. Circulation J. 2010; 74:213–220. #

41. Libby P. Inflammatory mechanisms: the molecular basis of inflammation and disease. Nutr Rev. 2007; 65:S140-S146.

42. Lintermans LL, Stegeman CA, Heeringa P, Abdulahad WH. T cells in vascular inflammatory diseases. Front Immunol. 2014; 5:504.

43. Liu CH, Abrams ND, Carrick DM, Chander P, Dwyer J, Hamlet MRJ, Macchiarini F, PrabhuDas M, Shen GL, Tandon P, Vedamony MM. Biomarkers of chronic inflammation in disease development and prevention: challenges and opportunities. Nat Immunol. 2017 Oct 18;18(11):1175-1180.

44. Malmivuo J, Plonsey R. Biolectromagnetism, Principles and Applications of Bioelectric and Biomagnetic Fields. New York Oxford, Oxford University Press, 1995.

45. McMakin CR, Gregory WM, Phillips TM. Cytokine changes with microcurrent treatment of fibromyalgia associated with spine trauma. Journal of Bodywork and Movement Therapies. 2005, 9, 169-176.

46. Medzhitov R. Inflammation 2010: new adventures of an old flame. Cell. 2010; 140:771–776.

47. Micheli DC, Fernandes PC, Jr, Cruvinel JC, Nomelini ID, Murta EF, Tavares-Murta BM. Circulating cytokines and nitric oxide are involved in the Inhibition of Neutrophil Migration in patients with Uterine Cervical Neoplasia. Clin Med Insights Oncol. 2012;6:233–242.

48. Milenkovic VM, Stanton EH, Nothdurfter C, Rupprecht R, Wetzel CH. The Role of Chemokines in the Pathophysiology of Major Depressive Disorder. Int J Mol Sci. 2019 May 09;20(9).

49. Nathan C, Ding A. Nonresolving inflammation. Cell. 2010; 140:871–882.

50. Needham EJ, Helmy A, Zanier ER, Jones JL, Coles AJ, Menon DK. The immunological response to traumatic brain injury. J Neuroimmunol. 2019 Jul 15;332:112-125.

51. Netea MG, Balkwill F, Chonchol M et al., A guiding map for inflammation. Nat. Immunol, 2017, 18, 826–831.

52. Ouyang BS, Che JL, Yin Zhang JG, et al. Effects of electroacupuncture and simple acupuncture on changes of IL-1, IL-4, IL-6 and IL-10 in peripheral blood and joint fluid in patients with rheumatoid arthritis. (Chinese Study) Zhongguo Zhen Jiu. 2010 Oct;30(10):840-4.

53. Ouyang BS, Gao J, Che JL, et al. Effect of electro-acupuncture on tumor necrosis factor-α and vascular endothelial growth factor in peripheral blood and joint synovia of patients with rheumatoid arthritis. Chin J of Integr Med. 2011 Jul;17(7):505-9. doi: 10.1007/s11655-011-0783-2. Epub 2011 Jul 3.

54. Packard RRS, Libby P. Inflammation in atherosclerosis: from vascular biology to biomarker discovery and risk prediction. Clin Chem. 2008; 54:24–38.

55. Ren XF, Li WZ, Meng FY, Lin CF. Differential effects of propofol and isoflurane on the activation of T-helper cells in lung cancer patients. Anaesthesia. 2010;65:478–482. doi: 10.1111/j.1365-2044.2010.06304.x

56. Rosique RG, Rosique MJ, Farina JA. Curbing Inflammation in Skin Wound Healing: A Review. International Journal of Inflammation Volume 2015, Article ID 316235, 9 pages http://dx.doi.org/10.1155/2015/316235

57. Sato KL, Sanada LS, Duarte da Silva M, Rodrigo Okubo R, Sluka KA. Transcutaneous electrical nerve stimulation, acupuncture, and spinal cord stimulation on neuropathic, inflammatory and, non-inflammatory pain in rat models. Korean J Pain. 2020 Apr 1;33(2):121-130. doi: 10.3344/kjp.2020.33.2.121.

58. Scott D, Frederick W, Huizinga TW. Rheumatoid arthritis. Lancet 2010 Sep 25;376(9746):1094-108. doi: 10.1016/S0140-6736(10)60826-4.

59. Slavich GM Understanding inflammation, its regulation, and relevance for health: a top scientific and public priority. Brain Behav. Immun, 2015, 45, 13–14.

60. Song C, Halbreich U, Han C, et al. Imbalance between pro- and anti-inflammatory cytokines, and between Th1 and Th2 cytokines in depressed patients: the effect of electroacupuncture or fluoxetine treatment. Pharmacopsychiatry. 2009 Sep;42(5):182-8. doi: 10.1055/s-0029-1202263. Epub 2009 Sep 1.

61. Sprott, H. What can rehabilitation interventions achieve in patients with primary fibromyalgia? Current Opinion in Rheumatology. 2003, 15 (2),145-150.

62. Straub RH. The brain and immune system prompt energy shortage in chronic inflammation and ageing. Nat. Rev. Rheumatol, 2017, 13, 743–751.

63. Strober W, Fuss I, Mannon P. The fundamental basis of inflammatory bowel disease. J Clin Invest. 2007; 117:514–521.

64. Takeuchi O, Akira S. Pattern Recognition Receptors and Inflammation. Cell. 2010; 140:805–820.

65. Tsalamandris S, Antonopoulos AS, Evangelos Oikonomou E, et al., The Role of Inflammation in Diabetes: Current Concepts and Future Perspectives. Euro Cardiol, 2019 Apr; 14(1): 50–59.

66. Wang Y, Gehringer R, Mousa SA, Hackel D, Brack A, Rittner LR. CXCL10 Controls Inflammatory Pain via Opioid Peptide-Containing Macrophages in Electroacupuncture, 2014, PLoS ONE 9(4): e94696. doi:10.1371/journal.pone.0094696

67. Watson T. Electrotherapy, Evidence Based Practice. Churchill Livingston, Elsevier, 2008.

68. Wu H, Wang K , Li G , Meng D, Hang J, Wang W, Li Y. Effects of transcutaneous acupoint electrical stimulation on the imbalance of Th1, Th2, Th17 and Treg cells following thoracotomy of patients with lung cancer. Experimental and Therapeutic Medicine, 2016, 11: 495-502.

69. . Yousuf A, Ibrahim W, Greening NJ, Brightling CE. T2 Biologics for Chronic Obstructive Pulmonary Disease. J Allergy Clin Immunol Pract. 2019 May - Jun;7(5):1405-1416.

70. . Zhou Y, Hong Y, Huang H. Triptolide Attenuates Inflammatory Response in Membranous Glomerulo- Nephritis Rat via Downregulation of NF-κB Signaling Pathway. Kidney and Blood Pressure Res. 2016; 41:901–910.