Interleukin-6 response to exercise and high-altitude exposure: influence of alpha-adrenergic blockade

Exposure to normobaric hypoxia shapes the acute inflammatory response in human whole blood cells in vivo

Cells of the immune defence, especially leukocytes, often have to perform their function in tissue areas that are characterized by oxygen deficiency, so-called hypoxia. Physiological hypoxia significantly affects leukocyte function and controls the innate and adaptive immune response mainly through transcriptional gene regulation via the hypoxia-inducible factors (HIFs). Multiple pathogens including components of bacteria, such as lipopolysaccharides (LPS) trigger the activation of leukocytes. HIF pathway activation enables immune cells to adapt to both hypoxic environments in physiological and inflammatory settings and modulates immune cell responses through metabolism changes and crosstalk with other immune-relevant signalling pathways. To study the mutual influence of both processes in vivo, we used a human endotoxemia model, challenging participants with an intravenous LPS injection post or prior to a 4-h stay in a hypoxic chamber with normobaric hypoxia of 10.5% oxygen. We analysed changes in gene expression in whole blood cells and determined inflammatory markers to unveil the crosstalk between both processes. Our investigations showed differentially altered gene expression patterns of HIF and target genes upon in vivo treatment with LPS and hypoxia. Further, we found evidence for effects of hypoxic priming upon inflammation in combination with immunomodulatory effects in whole blood cells in vivo. Our work elucidates the complex interplay of hypoxic and inflammatory HIF regulation in human immune cells and offers new perspectives for further clinical research.

Recommendations for Women in Mountain Sports and Hypoxia Training/Conditioning

The (patho-)physiological responses to hypoxia are highly heterogeneous between individuals. In this review, we focused on the roles of sex differences, which emerge as important factors in the regulation of the body's reaction to hypoxia. Several aspects should be considered for future research on hypoxia-related sex differences, particularly altitude training and clinical applications of hypoxia, as these will affect the selection of the optimal dose regarding safety and efficiency. There are several implications, but there are no practical recommendations if/how women should behave differently from men to optimise the benefits or minimise the risks of these hypoxia-related practices. Here, we evaluate the scarce scientific evidence of distinct (patho)physiological responses and adaptations to high altitude/hypoxia, biomechanical/anatomical differences in uphill/downhill locomotion, which is highly relevant for exercising in mountainous environments, and potentially differential effects of altitude training in women. Based on these factors, we derive sex-specific recommendations for mountain sports and intermittent hypoxia conditioning: (1) Although higher vulnerabilities of women to acute mountain sickness have not been unambiguously shown, sex-dependent physiological reactions to hypoxia may contribute to an increased acute mountain sickness vulnerability in some women. Adequate acclimatisation, slow ascent speed and/or preventive medication (e.g. acetazolamide) are solutions. (2) Targeted training of the respiratory musculature could be a valuable preparation for altitude training in women. (3) Sex hormones influence hypoxia responses and hormonal-cycle and/or menstrual-cycle phases therefore may be factors in acclimatisation to altitude and efficiency of altitude training. As many of the recommendations or observations of the present work remain partly speculative, we join previous calls for further quality research on female athletes in sports to be extended to the field of altitude and hypoxia.

Treatment of recurrent hunting-associated respiratory distress episodes in 2 dogs

Noncardiogenic pulmonary edema (NCPE) in hunting dogs is an uncommon and poorly described condition for which no preventive treatment is available. Two dogs were presented for recurrent respiratory distress strictly associated with hunting activities. Diagnosis was based on bilateral, symmetrical, interstitial-to-alveolar pattern in the caudodorsal lung fields on thoracic radiographs, exclusion of other causes, and spontaneous clinical and radiographic improvement. Considering that the pathogenesis of exercise-induced NCPE likely involves α- and β-adrenergic overstimulation, treatment with sympathetic blockers was used in both dogs. The first dog no longer showed respiratory signs during hunting activities. However, treatment failed to prevent respiratory distress in the other dog. Based on the large number of red blood cells in the bronchoalveolar lavage fluid of the second dog, exercise-induced pulmonary hemorrhage was suspected, as described in racing horses. The loop diuretic furosemide successfully prevented further hunting-associated respiratory distress episodes in this dog.

Global REACH 2018: High Altitude-Related Circulating Extracellular Microvesicles Promote a Proinflammatory Endothelial Phenotype In Vitro

Brewster, L. Madden, Anthony R. Bain, Vinicius P. Garcia, Noah M. DeSouza, Michael M. Tymko, Jared J. Greiner, and Philip N. Ainslie. Global REACH 2018: high altitude-related circulating extracellular microvesicles promote a proinflammatory endothelial phenotype in vitro. High Alt Med Biol. 24:223-229, 2023. Introduction: Ascent to high altitude (HA) can induce vascular dysfunction by promoting a proinflammatory endothelial phenotype. Circulating microvesicles (MVs) can mediate the vascular endothelium and inflammation. It is unclear whether HA-related MVs are associated with endothelial inflammation. Objectives: We tested the hypothesis that MVs derived from ascent to HA induce a proinflammatory endothelial phenotype. Methods: Ten healthy adults (8 M/2 F; age: 28 ± 2 years) residing at sea level (SL) were studied before and 4-6 days after rapid ascent to HA (4,300 m). MVs were isolated and enumerated from plasma by centrifugation and flow cytometry. Human umbilical vein endothelial cells were treated with MVs collected from each subject at SL (MV-SL) and at HA (MV-HA). Results: Circulating MV number significantly increased at HA (26,637 ± 3,315 vs. 19,388 ± 1,699). Although intracellular expression of total nuclear factor kappa beta (NF-κB; 83.4 ± 6.7 arbitrary units [AU] vs. 90.2 ± 6.9 AU) was not affected, MV-HA resulted in ∼55% higher (p < 0.05) active NF-κB (129.6 ± 19.8 AU vs. 90.7 ± 10.5 AU) expression compared with MV-SL. In addition, MV-HA induced higher interleukin (IL)-6 (63.9 ± 3.9 pg/ml vs. 53.3 ± 3.6 pg/ml) and IL-8 (140.2 ± 3.6 pg/ml vs. 120.7 ± 3.8 pg/ml) release compared with MV-SL, which was blunted with NF-κB blockade. Conclusions: Circulating extracellular MVs increase at HA and induce endothelial inflammation, potentially contributing to altitude-related vascular dysfunction.

Impact of Exercise in Hypoxia on Inflammatory Cytokines in Adults: A Systematic Review and Meta-analysis

BACKGROUND

Both acute exercise and environmental hypoxia may elevate inflammatory cytokines, but the inflammatory response in the hypoxic exercise is remaining unknown.

OBJECTIVE

We performed this systematic review and meta-analysis to examine the effect of exercise in hypoxia on inflammatory cytokines, including IL-6, TNF-α and IL-10.

METHODS

PubMed, Scopus and Web of Science were searched to identify the original articles that compared the effect of exercise in hypoxia with normoxia on IL-6, TNF-α and IL-10 changes, published up to March 2023. Standardized mean differences and 95% confidence intervals (CIs) were calculated using a random effect model to (1) determine the effect of exercise in hypoxia, (2) determine the effect of exercise in normoxia and (3) compare the effect of exercise in hypoxia with normoxia on IL-6, TNF-α and IL-10 responses.

RESULTS

Twenty-three studies involving 243 healthy, trained and athlete subjects with a mean age range from 19.8 to 41.0 years were included in our meta-analysis. On comparing exercise in hypoxia with normoxia, no differences were found in the response of IL-6 [0.17 (95% CI - 0.08 to 0.43), p = 0.17] and TNF-α [0.17 (95% CI - 0.10 to 0.46), p = 0.21] between the conditions. Exercise in hypoxia significantly increased IL-10 concentration [0.60 (95% CI 0.17 to 1.03), p = 0.006] compared with normoxia. In addition, exercise during both hypoxia and normoxia increased IL-6 and IL-10, whereas TNF-α was increased only in hypoxic exercise condition.

CONCLUSION

Overall, exercise in both hypoxia and normoxia increased inflammatory cytokines; however, hypoxic exercise may lead to a greater inflammatory response in adults.

Can Maternal Exercise Prevent High-Altitude Pulmonary Hypertension in Children?

Leslie, Eric, Ann L. Gibson, Laura V. Gonzalez Bosc, Christine Mermier, Sean M. Wilson, and Michael R. Deyhle. Review: can maternal exercise prevent high-altitude pulmonary hypertension in children? High Alt Med Biol. 24:1-6, 2023.-Chronic high-altitude exposure reduces oxygen delivery to the fetus during pregnancy and causes pathologic pulmonary artery remodeling, This increases the risk of high-altitude pulmonary hypertension (PH), which is a particularly fatal disease that is difficult to treat. Therefore, finding ways to prevent high-altitude PH, including during the neonatal period, is preferable. Cardiorespiratory exercise can improve functional capacity and quality of life in patients with high-altitude PH. However, similar to other treatments and surgical procedures, the benefits are not enough to cure the disease after a diagnosis. Cardiorespiratory exercise by mothers during pregnancy (i.e., maternal exercise) has not been previously evaluated to prevent the development of high-altitude PH in children born and living at high altitude. This focused review describes the pathophysiology of high-altitude PH and the potential benefit of maternal exercise for preventing the disease caused by high-altitude pregnancies.

Neuroinflammation mechanisms of neuromodulation therapies for anxiety and depression

Mood disorders are associated with elevated inflammation, and the reduction of symptoms after multiple treatments is often accompanied by pro-inflammation restoration. A variety of neuromodulation techniques that regulate regional brain activities have been used to treat refractory mood disorders. However, their efficacy varies from person to person and lack reliable indicator. This review summarizes clinical and animal studies on inflammation in neural circuits related to anxiety and depression and the evidence that neuromodulation therapies regulate neuroinflammation in the treatment of neurological diseases. Neuromodulation therapies, including transcranial magnetic stimulation (TMS), transcranial electrical stimulation (TES), electroconvulsive therapy (ECT), photobiomodulation (PBM), transcranial ultrasound stimulation (TUS), deep brain stimulation (DBS), and vagus nerve stimulation (VNS), all have been reported to attenuate neuroinflammation and reduce the release of pro-inflammatory factors, which may be one of the reasons for mood improvement. This review provides a better understanding of the effective mechanism of neuromodulation therapies and indicates that inflammatory biomarkers may serve as a reference for the assessment of pathological conditions and treatment options in anxiety and depression.

Effects of Interval Training Under Hypoxia on Hematological Parameters, Hemodynamic Function, and Endurance Exercise Performance in Amateur Female Runners in Korea

Interval training under hypoxia (IHT) is commonly used to enhance endurance exercise performance. However, previous studies examining hematologic changes related to the immune system that affect health and conditioning are lacking. This study aimed to evaluate the effects of IHT for 6-weeks on hematological parameters, hemodynamic function, and endurance exercise performance in amateur Korean female runners. Twenty healthy amateur Korean female runners (age: 24.85 ± 3.84 years) were equally assigned to normoxic training group (NTG) for interval training under normoxia (760 mmHg) and hypoxic training group (HTG) for interval training under hypobaric hypoxia (526 mmHg, 3000 m simulated altitude) according to their body composition and endurance exercise performance. All participants performed 120-min of training sessions, consisting of 20-min of warm-up, 60-min of interval training, and 20-min of cool-down. The training program was performed 3-days per week for 6-weeks. Warm-up and cool-down were performed for 20-min at 60% maximal heart rate (HRmax). The interval training sessions comprised 10 repetitions of interval exercise (5-min of exercise corresponding to 90–95% HRmax and 1-min of rest) on a treadmill. All participants underwent measurements of hematological parameters, hemodynamic function, and endurance exercise performance before and after training. Both groups showed a significant increase in erythropoietin (EPO) level and a decrease in monocyte abundance, with EPO showing a greater increase in the HTG than in the NTG. B cell abundance significantly increased in the NTG; hematocrit and neutrophil counts significantly increased, and lymphocyte counts significantly decreased in the HTG. The HTG showed a significant improvement in oxygen uptake, stroke volume index, and end-diastolic volume index compared to the NTG. In addition, both groups showed significant improvements in heart rate, end-systolic volume index, and cardiac output index. The maximal oxygen uptake and 3000 m time trial record were significantly improved in both groups, and the HTG showed a tendency to improve more than the NTG. In conclusion, the IHT was effective in enhancing endurance exercise performance through improved hemodynamic function. Furthermore, hematological parameters of immune system showed a normal range before and after training and were not negatively affected.

The Effect of Chronic Intermittent Hypobaric Hypoxia on Sleep Quality and Melatonin Serum Levels in Chilean Miners

High-altitude mining is an important economic resource for Chile. These workers are exposed to chronic intermittent hypobaric hypoxia (CIHH), which reduces their sleep quality and increases the risk of accidents and long-term illnesses. Melatonin, a hormone produced by the pineal gland, is a sleep inducer that regulates the circadian cycle and may be altered in populations subjected to CIHH. This work aimed to assess the relationship between altitude, sleep quality, and plasma melatonin concentrations in miners with CIHH exposure. 288 volunteers were recruited from five altitudes (0, 1,600, 2,500, 3,500, and 4,500 m). All volunteers worked for 7 days at altitude, followed by 7 days of rest at sea level. We performed anthropometric assessments, nocturnal oximetry, sleep quality and sleepiness surveys, and serum melatonin levels upon awakening. Although oxygen saturation progressively decreased and heart rate increased at higher altitudes, subjective perception of sleep quality was not significantly different, and sleepiness increased in all groups compared to population at sea level. Similarly, melatonin levels increased at all assessed altitudes compared to the population at sea level. These data confirm that sleep disturbances associated with CIHH increase morning melatonin levels. Therefore, this hormone and could potentially serve as a biomarker of sleep quality.

Influence of Zinc on the Acute Changes in Erythropoietin and Proinflammatory Cytokines with Hypoxia

Baranauskas, Marissa N., Joseph Powell, Alyce D. Fly, Bruce J. Martin, Timothy D. Mickleborough, Hunter L. Paris, and Robert F. Chapman. Influence of zinc on the acute changes in erythropoietin and proinflammatory cytokines with hypoxia. High Alt Med Biol. 22: 148-156, 2021. Background: Considerable, unexplained, interindividual variability characterizes the erythropoietin (EPO) response to hypoxia, which can impact hematological acclimatization for individuals sojourning to altitude. Zinc supplementation has the potential to alter EPO by attenuating increases in inflammation and oxidative stress. Yet, the application of such an intervention has not been evaluated in humans. In this proof-of-concept study, we aimed to evaluate the EPO and inflammatory responses to acute hypoxia in human participants following chronic zinc supplementation. Methods: Nine physically active participants (men n = 5, women n = 4, age 28 ± 4 years, height 176 ± 11 cm, mass 77 ± 21 kg) were exposed to 12 hours of normobaric hypoxia simulating an altitude of 3,000 m (F_iO₂ = 0.14) before and after 8 weeks of supplementation with 40 mg/day of elemental zinc from picolinate. Blood samples for subsequent analysis of serum zinc, EPO, superoxide dismutase (extracellular superoxide dismutase [EC-SOD]), C-reactive protein (CRP), and proinflammatory cytokines were obtained pre- and postsupplementation and exposure to hypoxia. Results: After zinc supplementation, EPO increased by 64.9 ± 36.0% (mean ± standard deviation) following 12 hours of hypoxia, but this response was not different from presupplementation (70.8 ± 46.1%). Considerable interindividual (range: -1% to +208%) variability was apparent in the acute EPO response. While most markers of inflammation did not change with hypoxia, interleukin-6 concentrations increased from 1.17 ± 0.05 to 1.97 ± 0.32 pg/ml during the final 6 hours. The acute EPO response at 12 hours was not related to changes in serum zinc, EC-SOD, CRP, or proinflammatory cytokines. Conclusions: Zinc supplementation does not influence the acute EPO or inflammatory response with short-term exposure to moderate levels of normobaric hypoxia (3,000 m) in apparently healthy young adults.

Interval Hypoxic Training Enhances Athletic Performance and Does Not Adversely Affect Immune Function in Middle- and Long-Distance Runners

This study evaluated the effects of intermittent interval training in hypoxic conditions for six weeks compared with normoxic conditions, on hemodynamic function, autonomic nervous system (ANS) function, immune function, and athletic performance in middle- and long-distance runners. Twenty athletes were divided into normoxic training (normoxic training group (NTG); n = 10; residing and training at sea level) and hypoxic training (hypoxic training group (HTG); n = 10; residing at sea level but training in 526-mmHg hypobaric hypoxia) groups. All dependent variables were measured before, and after, training. The training frequency was 90 min, 3 d per week for six weeks. Body composition showed no significant difference between the two groups. However, the HTG showed more significantly improved athletic performance (e.g., maximal oxygen uptake). The hemodynamic function (e.g., oxygen uptake, oxygen pulse, and cardiac output) during submaximal exercise and ANS function (e.g., standard deviation and root mean square of successive differences, high frequency, and low/high frequency) improved more in the HTG. Immune function parameters were stable within the normal range before and after training in both groups. Therefore, hypoxic training was more effective in enhancing athletic performance, and improving hemodynamic and ANS function; further, it did not adversely affect immune function in competitive runners.

Effects of 2-Week Exercise Training in Hypobaric Hypoxic Conditions on Exercise Performance and Immune Function in Korean National Cycling Athletes with Disabilities: A Case Report

We aimed to evaluate the effects of a 2-week exercise training program in hypobaric hypoxic conditions on exercise performance and immune function in Korean national cycling athletes with disabilities. Six Korean national cycling athletes with disabilities participated in exercise training consisting of continuous aerobic exercise and anaerobic interval exercise in hypobaric hypoxic conditions. The exercise training frequency was 60 min (5 days per week for 2 weeks). Before and after the exercise training, exercise performance and immune function were measured in all athletes. Regarding the exercise performance parameters, the 3-km time trial significantly decreased and blood lactate levels after the 3-km time trial test significantly increased by exercise training in hypobaric hypoxic conditions. Regarding the oxygen-transporting capacity, significant differences were not observed. Regarding immune function, the number of leukocytes and natural killer cells significantly decreased and that of eosinophils, B cells, and T cells significantly increased. These results indicated that our 2-week hypoxic training showed the potential to improve exercise performance in Korean national disabled athletes. However, the effects of our hypoxic training method on immune function remained unclear.

Acute Inflammatory Responses to Exercise in Patients with Abdominal Aortic Aneurysm

PURPOSE

Inflammation and extracellular matrix degeneration contribute to abdominal aortic aneurysm (AAA) development. We aimed to assess the effect of exercise intensity on circulating biomarkers of inflammation and extracellular matrix degeneration in patients with AAA and healthy older adults.

METHODS

Twenty patients with AAA (74 ± 6 yr) and 20 healthy males (72 ± 5 yr) completed moderate-intensity cycling at 40% peak power output, higher-intensity intervals at 70% peak power output, and control (rest) on separate days. Circulating matrix metalloproteinase-9 (MMP-9), transforming growth factor beta 1, interleukin-6 (IL-6), IL-10, and tumor necrosis factor alpha (TNF-α) were analyzed at rest and 0 to 90 min postexercise.

RESULTS

Biomarkers at baseline were similar between groups. IL-6 responses to exercise were similar between groups, with a greater increase in ΔIL-6 after moderate-intensity compared with higher-intensity exercise (P < 0.001). Delta MMP-9 showed a 118-ng·mL (95% confidence interval = 23 to 214, P = 0.02) greater increase immediately after higher-intensity exercise compared with changes in control in both groups. Delta MMP-9 then decreased by 114 ng·mL (18 to 211, P = 0.02) 90 min after higher-intensity exercise compared with the changes in control. Delta TNF-α was not different between protocols in healthy adults. In patients with AAA, delta TNF-α showed a greater decrease after higher-intensity compared with moderate-intensity exercise (-6.1 pg·mL, -8.5 to -3.6, P < 0.001) and control (-4.9 pg·mL, -7.4 to -2.4, P < 0.001). IL-10 and transforming growth factor beta 1 did not change in either group.

CONCLUSIONS

These findings suggest that a bout of higher-intensity exercise elicits a greater anti-inflammatory response compared with moderate-intensity exercise, which may be further augmented in patients with AAA. Exercise-induced reductions in biomarkers associated with AAA progression may represent a protective effect of exercise in patients with AAA.

Performance and altitude: Ways that nutrition can help

High altitudes are a challenge for human physiology and for sports enthusiasts. Several reasons lead to deterioration in performance at high altitudes. Hypoxia owing to high altitude causes a breakdown of homeostasis with imbalance in several physiological systems, including the immune system. The reduction in mucosal immunity and inflammation and the predominance of the humoral immune response causes a condition of immunosuppression and an increased likelihood of infection. In addition, it is known that worsening of the immune response is associated with reduced performance. On the other hand, immunonutrition plays an important role in modulating the effects of physical exercise on the immune system. However, to our knowledge, few studies have evaluated the effect of nutrition on the immune system after exercise in hypoxia. Although the association between exercise and hypoxia has been shown to be more severe for the body owing to the sum of stressful agents, supplementation with carbohydrates and glutamine seems to play a relevant role in mitigating immunosuppressive effects. These findings, although limited by the fact that they are the result of very few studies, shed light on a relevant theme for sports physiology and nutrition and suggest that both supplements may be useful for athletes, visitors, and workers in high-altitude regions. The aim of this review was to discuss the effects of high-altitude hypoxia on the human body from the point of view of exercise immunology because it is known that transient immunosuppression after strenuous exercise and competition should be followed by reduction in training overload and worse performance.

Impact of Endurance Exercise in Hypoxia on Muscle Damage, Inflammatory and Performance Responses

Sumi, D, Kojima, C, and Goto, K. Impact of endurance exercise in hypoxia on muscle damage, inflammatory and performance responses. J Strength Cond Res 32(4): 1053-1062, 2018-This study evaluated muscle damage and inflammatory and performance responses after high-intensity endurance exercise in moderate hypoxia among endurance athletes. Nine trained endurance athletes completed 2 different trials on different days: exercise under moderate hypoxia (H trial, FiO2 = 14.5%) and normoxia (N trial, FiO2 = 20.9%). They performed interval exercises (10 × 3-minute running at 95% of V[Combining Dot Above]O2max with 60-second of active rest at 60% of V[Combining Dot Above]O2max) followed by 30-minute of continuous running at 85% of V[Combining Dot Above]O2max under either hypoxic or normoxic conditions. Venous blood samples were collected 4 times: before exercise, 0, 60, and 120-minute after exercise. The time to exhaustion (TTE) during running at 90% of V[Combining Dot Above]O2max was also determined to evaluate endurance capacity 120-minute after the training session. The H trial induced a significantly greater exercise-induced elevation in the blood lactate concentration than did the N trial (p = 0.02), whereas the elevation in the exercise-induced myoglobin concentration (muscle damage marker) was significantly greater in the N trial than in the H trial (p = 0.005). There was no significant difference in plasma interleukin-6 (inflammatory marker) concentration between the H and N trials. The TTE was shorter in the N trial (613 ± 65 seconds) than in the H trial (783 ± 107 seconds, p = 0.02). In conclusion, among endurance athletes, endurance exercise under moderate hypoxic conditions did not facilitate an exercise-induced muscle damage response or cause a further reduction in the endurance capacity compared with equivalent exercise under normoxic conditions.

Muscle Fn14 gene expression is associated with fat-free mass retention during energy deficit at high altitude

Intramuscular factors that modulate fat-free mass (FFM) loss in lowlanders exposed to energy deficit during high-altitude (HA) sojourns remain unclear. Muscle inflammation may contribute to FFM loss at HA by inducing atrophy and inhibiting myogenesis via the tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and its receptor, fibroblast growth factor-inducible protein 14 (Fn14). To explore whether muscle inflammation modulates FFM loss reportedly developing during HA sojourns, muscle inflammation, myogenesis, and proteolysis were assessed in 16 men at sea level (SL) and following 21 days of energy deficit (-1862 ± 525 kcal/days) at high altitude (HA, 4300 m). Total body mass (TBM), FFM, and fat mass (FM) were assessed using DEXA. Gene expression and proteolytic enzymatic activities were assessed in muscle samples collected at rest at SL and HA. Participants lost 7.2 ± 1.8 kg TBM (P < 0.05); 43 ± 30% and 57 ± 30% of the TBM lost was FFM and FM, respectively. Fn14, TWEAK, TNF alpha-receptor (TNFα-R), TNFα, MYOGENIN, and paired box protein-7 (PAX7) were upregulated (P < 0.05) at HA compared to SL. Stepwise linear regression identified that Fn14 explained the highest percentage of variance in FFM loss (r2  = 0.511, P < 0.05). Dichotomization of volunteers into HIGH and LOW Fn14 gene expression indicated HIGH lost less FFM and more FM (28 ± 28% and 72 ± 28%, respectively) as a proportion of TBM loss than LOW (58 ± 26% and 42 ± 26%; P < 0.05) at HA. MYOGENIN gene expression was also greater for HIGH versus LOW (P < 0.05). These data suggest that heightened Fn14 gene expression is not catabolic and may protect FFM during HA sojourns.

Realising the Potential of Urine and Saliva as Diagnostic Tools in Sport and Exercise Medicine

Accurate monitoring of homeostatic perturbations following various psychophysiological stressors is essential in sports and exercise medicine. Various biomarkers are routinely used as monitoring tools in both clinical and elite sport settings. Blood collection and muscle biopsies, both invasive in nature, are considered the gold standard for the analysis of these biomarkers in exercise science. Exploring non-invasive methods of collecting and analysing biomarkers that are capable of providing accurate information regarding exercise-induced physiological and psychological stress is of obvious practical importance. This review describes the potential benefits, and the limitations, of using saliva and urine to ascertain biomarkers capable of identifying important stressors that are routinely encountered before, during, or after intense or unaccustomed exercise, competition, over-training, and inappropriate recovery. In particular, we focus on urinary and saliva biomarkers that have previously been used to monitor muscle damage, inflammation, cardiovascular stress, oxidative stress, hydration status, and brain distress. Evidence is provided from a range of empirical studies suggesting that urine and saliva are both capable of identifying various stressors. Although additional research regarding the efficacy of using urine and/or saliva to indicate the severity of exercise-induced psychophysiological stress is required, it is likely that these non-invasive biomarkers will represent "the future" in sports and exercise medicine.

Experimental intermittent ischemia augments exercise-induced inflammatory cytokine production

Acute exercise-induced inflammation is implicated in mediating the beneficial adaptations to regular exercise. Evidence suggests that reduced oxygen and/or blood flow to contracting muscle alters cytokine appearance. However, the acute inflammatory responses to hypoxic/ischemic exercise have been documented with inconsistent results and may not accurately reflect the ischemia produced during exercise in patients with ischemic cardiovascular diseases. Therefore, we determined the extent to which local inflammation is involved in the response to ischemic exercise. Fourteen healthy males performed unilateral isometric forearm contractions for 30 min with and without experimental ischemia. Blood was drawn at baseline, 5 and 10 min into exercise, at the end of exercise, and 30, 60, and 120 min after exercise. Oxygen saturation levels, as measured by near-infrared spectroscopy, were reduced by 10% and 41% during nonischemic and ischemic exercise, respectively. Nonischemic exercise did not affect cytokine values. Ischemia enhanced concentrations of basic fibroblast growth factor, interleukin (IL)-6, IL-10, tumor necrosis factor-alpha, and vascular endothelial growth factor during exercise, but IL-8 was not influenced by ischemic exercise. In conclusion, the present study demonstrates that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise.

NEW & NOTEWORTHY We demonstrate that ischemic, small-muscle endurance exercise elicits local inflammatory cytokine production compared with nonischemic exercise. The present study advances our knowledge of the inflammatory response to exercise in a partial ischemic state, which may be relevant for understanding the therapeutic effects of exercise training for people with ischemic cardiovascular disease-associated comorbidities.

The impact of inflammation on respiratory plasticity

Breathing is a vital homeostatic behavior and must be precisely regulated throughout life. Clinical conditions commonly associated with inflammation, undermine respiratory function may involve plasticity in respiratory control circuits to compensate and maintain adequate ventilation. Alternatively, other clinical conditions may evoke maladaptive plasticity. Yet, we have only recently begun to understand the effects of inflammation on respiratory plasticity. Here, we review some of common models used to investigate the effects of inflammation and discuss the impact of inflammation on nociception, chemosensory plasticity, medullary respiratory centers, motor plasticity in motor neurons and respiratory frequency, and adaptation to high altitude. We provide new data suggesting glial cells contribute to CNS inflammatory gene expression after 24h of sustained hypoxia and inflammation induced by 8h of intermittent hypoxia inhibits long-term facilitation of respiratory frequency. We also discuss how inflammation can have opposite effects on the capacity for plasticity, whereby it is necessary for increases in the hypoxic ventilatory response with sustained hypoxia, but inhibits phrenic long term facilitation after intermittent hypoxia. This review highlights gaps in our knowledge about the effects of inflammation on respiratory control (development, age, and sex differences). In summary, data to date suggest plasticity can be either adaptive or maladaptive and understanding how inflammation alters the respiratory system is crucial for development of better therapeutic interventions to promote breathing and for utilization of plasticity as a clinical treatment.

Effect of acute exercise and hypoxia on markers of systemic and mucosal immunity

Purpose

To determine how immune markers are affected by acute hypoxic exercise at the same relative intensity.

Methods

Twelve endurance-trained males (age: 28 ± 4 years, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max: 63.7 ± 5.3 mL/kg/min) cycled for 75 min at 70 % of altitude-specific \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max, once in normoxia (N) and once in hypobaric hypoxia equivalent to 2000 m above sea-level (H). Blood and saliva samples were collected pre-, post- and 2 h post-exercise.

Results

Participants cycled at 10.5 % lower power output in H vs. N, with no significant differences in heart rate (P = 0.10) or rating of perceived exertion (P = 0.21). Post-exercise plasma cortisol was higher in H vs. N [683 (95 % CI 576–810) nmol/l vs. 549 (469–643) nmol/l, P = 0.017]. The exercise-induced decrease in CD4:CD8 ratio was greater in H vs. N (−0.5 ± 0.2 vs. −0.3 ± 0.2, P = 0.019). There were no significant between-trial differences for adrenocorticotropic hormone, plasma cytokines, antigen-stimulated cytokine production, salivary immunoglobulin-A or lactoferrin. However, there was a main trial effect for concentration [F(11) = 5.99, P < 0.032] and secretion [F(11) = 5.01, P < 0.047] of salivary lysozyme, with this being higher in N at every time-point.

Conclusion

Whether the observed differences between H and N are of sufficient magnitude to clinically impair host defence is questionable, particularly as they are transient in nature and since other immune markers are unaffected. As such, acute hypoxic exercise likely does not pose a meaningful additional threat to immune function compared to exercise at sea level, provided that absolute workload is reduced in hypoxia so that relative exercise intensity is the same.

Vitamin E supplementation inhibits muscle damage and inflammation after moderate exercise in hypoxia

BACKGROUND

Exercise under hypoxic conditions represents an additional stress in relation to exercise in normoxia. Hypoxia induces oxidative stress and inflammation as mediated through tumour necrosis factor (TNF)-α release that might be exacerbated through exercise. In addition, vitamin E supplementation might attenuate oxidative stress and inflammation resulting from hypoxia during exercise. The present study aimed to evaluate the effects of vitamin E supplementation (250 mg) on inflammatory parameters and cellular damage after exercise under hypoxia simulating an altitude of 4200 m.

METHODS

Nine volunteers performed three sessions of 60 min of exercise (70% maximal oxygen uptake) interspersed for 1 week under normoxia, hypoxia and hypoxia after vitamin E supplementation 1 h before exercise. Blood was collected before, immediately after and at 1 h after exercise to measure inflammatory parameters and cell damage.

RESULTS

Percentage oxygen saturation of haemoglobin decreased after exercise and recovered 1 h later in the hypoxia + vitamin condition (P < 0.05). Supplementation decreased creatine kinase (CK)-TOTAL, CK-MB and lactate dehydrogenase 1 h after exercise (P < 0.05). The exercise in hypoxia increased interleukin (IL)-6, TNF-α, IL-1ra and IL-10 immediately after exercise (P < 0.05). Supplementation reversed the changes observed after exercise in hypoxia without supplementation (P < 0.05).

CONCLUSIONS

We conclude that 250 mg of vitamin E supplementation at 1 h before exercise reduces cell damage markers after exercise in hypoxia and changes the concentration of cytokines, suggesting a possible protective effect against inflammation induced by hypoxia during exercise.

Live high, train low - influence on resting and post-exercise hepcidin levels

The post-exercise hepcidin response during prolonged (>2 weeks) hypoxic exposure is not well understood. We compared plasma hepcidin levels 3 h after exercise [6 × 1000 m at 90% of maximal aerobic running velocity (vVO_2max )] performed in normoxia and normobaric hypoxia (3000 m simulate altitude) 1 week before, and during 14 days of normobaric hypoxia [196.2 ± 25.6 h (median: 200.8 h; range: 154.3-234.8 h) at 3000 m simulated altitude] in 10 well-trained distance runners (six males, four females). Venous blood was also analyzed for hepcidin after 2 days of normobaric hypoxia. Hemoglobin mass (Hb_mass ) was measured via CO rebreathing 1 week before and after 14 days of hypoxia. Hepcidin was suppressed after 2 (Cohen's d = -2.3, 95% confidence interval: [-2.9, -1.6]) and 14 days of normobaric hypoxia (d = -1.6 [-2.6, -0.6]). Hepcidin increased from baseline, 3 h post-exercise in normoxia (d = 0.8 [0.2, 1.3]) and hypoxia (d = 0.6 [0.3, 1.0]), both before and after exposure (normoxia: d = 0.7 [0.3, 1.2]; hypoxia: d = 1.3 [0.4, 2.3]). In conclusion, 2 weeks of normobaric hypoxia suppressed resting hepcidin levels, but did not alter the post-exercise response in either normoxia or hypoxia, compared with the pre-exposure response.

Decrease in circulating plasmacytoid dendritic cells during short-term systemic normobaric hypoxia

BACKGROUND

During exposure to high altitude, the immune system is altered. During hypoxia, an increase in interleukin (IL)-6 and high sensitivity C-reactive protein (hs-CRP), and an increase in natural killer cells and decrease in T cells in blood was shown. However, the impact of hypoxia on dendritic cells has not been investigated yet.

MATERIAL AND METHODS

Twelve healthy volunteers were subjected to a transient normobaric hypoxia for 6·5 h simulating an oxygen concentration at 5500 m. During exposure to hypoxia, blood samples were collected and analysed by flow cytometrical cell sorting (FACS) for circulating myeloid (mDCs) and plasmacytoid (pDCs) DCs. Serum levels of IL-6 and tumour necrosis factor (TNF)-α were analysed. In a cell culture hypoxia chamber, blood samples were subjected to the same hypoxia and analysed regarding DCs.

RESULTS

Exposure to normobaric hypoxia induced a significant decrease in circulating pDCs about 45% (P = 0·001) but not of mDC compared to baseline normoxia. Furthermore, we observed a significant increase of TNF-α about 340% (P = 0·03) and of IL-6 about 286% (P = 0·002). In cell culture experiments exposure of blood to hypoxia led to no significant changes in DCs, so that a direct cytotoxic effect was excluded. During hypoxia, we observed a transient increase in stromal-derived factor 1 (SDF-1) which is important for pDC tissue recruitment.

CONCLUSIONS

We show a significant decrease in circulating pDCs during hypoxia in parallel to a pro-inflammatory response. Further studies are necessary to evaluate whether the decrease in circulating pDCs might be the result of an enhanced tissue recruitment.

Influence of doxazosin on biosynthesis of S100A6 and atrial natriuretic factor peptides in the heart of spontaneously hypertensive rats

Hypertension frequently results in severe complications in cardiovascular system and histopathological changes in the heart. To better understand the cellular processes and signaling pathways responsible for the proper functioning of the heart, we decided to check whether doxazosin affects the density of structures containing S100A6 and atrial natriuretic factor in the heart of spontaneously hypertensive rats. The aim of this study is to find differences in the density of the structures containing S100A6 and atrial natriuretic factor in the heart of spontaneously hypertensive rats treated with doxazosin compared to untreated animals. Fragments of heart were collected from five spontaneously hypertensive rats and five spontaneously hypertensive rats receiving doxazosin for six weeks (dose 0.1 mg per 1 kg of body weight). On the paraffin sections S100A6 and atrial natriuretic factor peptides were localized in the heart using immunohistochemistry. Positive immunohistochemical reaction for S100A6 was observed in atrial and ventricular cardiomyocytes and in the coronary vasculature. In the heart of hypertensive rats treated with doxazosin the S100A6 immunoreactivity was significantly lower compared to untreated animals. Immunodetection of atrial natriuretic factor in the heart of rats confirmed presence of peptide in atrial myocardium. Delicate atrial natriuretic factor-immunoreactivity was observed also in few ventricular cardiomyocytes. The atrial natriuretic factor-immunosignal was significantly weaker in hearts of hypertensive rats receiving doxazosin compared to spontaneously hypertensive rats untreated. Since we found that doxazosin reduces the levels of S100A6 and atrial natriuretic factor peptides in the heart of spontaneously hypertensive rats, it can be assumed that cardiovascular disorders that occur in hypertension may be associated with disturbances of cellular processes and signaling pathways.

Remote ischemic preconditioning for prevention of high-altitude diseases: fact or fiction?

Preconditioning refers to exposure to brief episodes of potentially adverse stimuli and protects against injury during subsequent exposures. This was first described in the heart, where episodes of ischemia/reperfusion render the myocardium resistant to subsequent ischemic injury, which is likely caused by reactive oxygen species (ROS) and proinflammatory processes. Protection of the heart was also found when preconditioning was performed in an organ different from the target, which is called remote ischemic preconditioning (RIPC). The mechanisms causing protection seem to include stimulation of nitric oxide (NO) synthase, increase in antioxidant enzymes, and downregulation of proinflammatory cytokines. These pathways are also thought to play a role in high-altitude diseases: high-altitude pulmonary edema (HAPE) is associated with decreased bioavailability of NO and increased generation of ROS, whereas mechanisms causing acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) seem to involve cytotoxic effects by ROS and inflammation. Based on these apparent similarities between ischemic damage and AMS, HACE, and HAPE, it is reasonable to assume that RIPC might be protective and improve altitude tolerance. In studies addressing high-altitude/hypoxia tolerance, RIPC has been shown to decrease pulmonary arterial systolic pressure in normobaric hypoxia (13% O2) and at high altitude (4,342 m). Our own results indicate that RIPC transiently decreases the severity of AMS at 12% O2. Thus preliminary studies show some benefit, but clearly, further experiments to establish the efficacy and potential mechanism of RIPC are needed.

Changes in mitochondrial enzymatic activities of monocytes during prolonged hypobaric hypoxia and influence of antioxidants: A randomized controlled study

OBJECTIVES

Exposure to high altitudes is associated with oxidative cellular damage due to the increased level of reactive oxygen and nitrogen species and altered activity of antioxidant systems. Subjects were submitted to prolonged hypoxia, to evaluate changes in mitochondrial enzyme activities of monocytes and their attenuation by supplementation with antioxidants.

METHODS

Twelve subjects were randomly assigned to receive antioxidant supplements or placebo prior to and during an expedition to Pik Lenin (7145 m). Monocytes were isolated from blood samples to determine the activity of mitochondrial enzymes cytochrome c oxidase and citrate synthase at 490 m (baseline) and at the altitudes of 3550 m, 4590 m, and 5530 m.

RESULTS

An increase in citrate synthase activity at all altitudes levels was observed. Hypoxia induced an increase in the activity of cytochrome c oxidase only at 4590 m. Neither citrate synthase activity nor cytochrome c oxidase activity differed between the subjects receiving antioxidant supplements and those receiving placebo.

CONCLUSIONS

Hypoxia leads to an increase in citrate synthase activity of monocyte mitochondria as a marker of mitochondrial mass, which is not modified by antioxidant supplementation. The increase in mitochondrial mass may represent a compensatory mechanism to preserve oxidative phosphorylation of monocytes at high altitudes.

Widespread signals of convergent adaptation to high altitude in Asia and america

Living at high altitude is one of the most difficult challenges that humans had to cope with during their evolution. Whereas several genomic studies have revealed some of the genetic bases of adaptations in Tibetan, Andean, and Ethiopian populations, relatively little evidence of convergent evolution to altitude in different continents has accumulated. This lack of evidence can be due to truly different evolutionary responses, but it can also be due to the low power of former studies that have mainly focused on populations from a single geographical region or performed separate analyses on multiple pairs of populations to avoid problems linked to shared histories between some populations. We introduce here a hierarchical Bayesian method to detect local adaptation that can deal with complex demographic histories. Our method can identify selection occurring at different scales, as well as convergent adaptation in different regions. We apply our approach to the analysis of a large SNP data set from low- and high-altitude human populations from America and Asia. The simultaneous analysis of these two geographic areas allows us to identify several candidate genome regions for altitudinal selection, and we show that convergent evolution among continents has been quite common. In addition to identifying several genes and biological processes involved in high-altitude adaptation, we identify two specific biological pathways that could have evolved in both continents to counter toxic effects induced by hypoxia.

The impact of submaximal exercise during heat and/or hypoxia on the cardiovascular and monocyte HSP72 responses to subsequent (post 24 h) exercise in hypoxia

BACKGROUND

The aims of this study were to describe the cellular stress response to prolonged endurance exercise in acute heat, hypoxia and the combination of heat and hypoxia and to determine whether prior acute exposure to these stressors improved cellular tolerance to a subsequent exercise bout in hypoxia 24 h later.

METHODS

Twelve males (age 22 ± 4 years, height 1.77 ± 0.05 m, mass 79 ± 12.9 kg, VO2 max 3.57 ± 0.7 L · min(-1)) completed four trials (30-min rest, 90-min cycling at 50% normoxic VO2 max) in normothermic normoxia (NORM; 18°C, FIO2 = 0.21), heat (HEAT; 40°C, 20% RH), hypoxia (HYP; FIO2 = 0.14) or a combination of heat and hypoxia (COM; 40°C, 20% RH, FIO2 = 0.14) separated by at least 7 days. Twenty-four hours after each trial, participants completed a hypoxic stress test (HST; 15-min rest, 60-min cycling at 50% normoxic VO2 max, FIO2 = 0.14). Monocyte heat shock protein 72 (mHSP72) was assessed immediately before and after each exercise bout.

RESULTS

mHSP72 increased post exercise in NORM (107% ± 5.5%, p > 0.05), HYP (126% ± 16%, p < 0.01), HEAT (153% ± 14%, p < 0.01) and COM (161% ± 32%, p < 0.01). mHSP72 had returned to near-resting values 24 h after NORM (97% ± 8.6%) but was elevated after HEAT (130% ± 19%), HYP (118% ± 17%) and COM (131% ± 19%) (p < 0.05). mHSP72 increased from baseline after HSTNORM (118% ± 12%, p < 0.05), but did not increase further in HSTHEAT, HSTHYP and HSTCOM.

CONCLUSIONS

The prior induction of mHSP72 as a result of COM, HEAT and HYP attenuated further mHSP72 induction after HST and was indicative of conferred cellular tolerance.

Pathogenic roles of the carotid body inflammation in sleep apnea

Breathing difficulties in sleep are a hallmark of sleep-disordered breathing commonly observed in patients with sleep disorders. The pathophysiology of sleep apnea is in part due to an augmented activity of the carotid body chemoreflex. Arterial chemoreceptors in the carotid body are sensitive to inflammatory cytokines and immunogenic molecules in the circulation, because cytokine receptors are expressed in the carotid body in experimental animals and human. Intriguingly, proinflammatory cytokines are also locally produced and released in the carotid body. Also, there are significant increases in the expression of proinflammatory cytokines, cytokine receptors, and inflammatory mediators in the carotid body under hypoxic conditions, suggesting an inflammatory response of the carotid body. These upregulated cytokine signaling pathways could enhance the carotid chemoreceptor activity, leading to an overactivity of the chemoreflex adversely effecting breathing instability and autonomic imbalance. This review aims to summarize findings of the literature relevant to inflammation in the carotid body, with highlights on the pathophysiological impact in sleep apnea. It is concluded that local inflammation in the carotid body plays a pathogenic role in sleep apnea, which could potentially be a therapeutic target for the treatment of the pathophysiological consequence of sleep apnea.

Changes in the levels of cytokines in both diabetic/non-diabetic type I children living in a moderate altitude area in Saudi Arabia

The aim of the present study was to investigate the possible effects of living in moderate altitude area on pro/anti-inflammatory cytokines profile (IFN-γ, TNF-α, IL-6, IL-1β, IL-10, and IL-4) among type I diabetic (T1D) and non- T1D children compared with those living at sea level area. A prospective clinical study was carried out at pediatric outpatient endocrine clinics in Taif City, which is a moderate altitude area in Saudi Arabia, that stands about 1800-2000 meters above sea-level; and in Mecca City, which is a sea level area, that lies in the middle west of Saudi Arabia. Hemoglobin A1c (HbA1c) percentage was estimated and cytokine measurements were performed in sera by flow cytometry using Cytometric Bead Array (CBA) technology. In this study we included 600 children who were consecutively enrolled (sex and age were matched). The HbA1c was statistically significantly higher in children living in moderate altitude compared to those living at sea level (overall p<0.001). Furthermore, T1D patients had higher values of serum cytokine levels (IFN-γ, TNF-α, IL-6, IL-1β, IL-4, and IL-10) in comparison to non-T1D control group (overall p<0.001). In conclusion, the data of the present study clearly showed that in both T1D and non-T1D children, moderate altitude-natives expressed high HbA1c and both pro-and anti-inflammatory cytokines. Type I diabetic children living in moderate altitude or at sea level showed elevated levels of IFN-γ, TNF-α, IL-6, IL-1β, IL-4, and IL-10 than control subjects. Glycemic control in non-diabetic children was affected by living in moderate altitude, however, HbA1c significantly increased in diabetic children living in moderate altitude.

The biology of depression in cancer and the relationship between depression and cancer progression

The prevalence of depressive symptoms in patients with cancer exceeds that observed in the general population and depression is associated with a poorer prognosis in cancer patients. The increased prevalence is not solely explained by the psychosocial stress associated with the diagnosis. Pro-inflammatory cytokines, which induce sickness behaviour with symptoms overlapping those of clinical depression, are validated biomarkers of increased inflammation in patients with cancer. A growing literature reveals that chronic inflammatory processes associated with stress may also underlie depression symptoms in general, and in patients with cancer in particular. Therapeutic modalities, which are frequently poorly tolerated, are used in the treatment of cancer. These interventions are associated with inflammatory reactions, which may help to explain their toxicity. There is evidence that antidepressants can effectively treat symptoms of depression in cancer patients though the database is meager. Novel agents with anti-inflammatory properties may be effective alternatives for patients with treatment-resistant depression who exhibit evidence of increased inflammation.

High-altitude pulmonary edema

High-altitude pulmonary edema (HAPE), a not uncommon form of acute altitude illness, can occur within days of ascent above 2500 to 3000 m. Although life-threatening, it is avoidable by slow ascent to permit acclimatization or with drug prophylaxis. The critical pathophysiology is an excessive rise in pulmonary vascular resistance or hypoxic pulmonary vasoconstriction (HPV) leading to increased microvascular pressures. The resultant hydrostatic stress causes dynamic changes in the permeability of the alveolar capillary barrier and mechanical injurious damage leading to leakage of large proteins and erythrocytes into the alveolar space in the absence of inflammation. Bronchoalveolar lavage and hemodynamic pressure measurements in humans confirm that elevated capillary pressure induces a high-permeability noninflammatory lung edema. Reduced nitric oxide availability and increased endothelin in hypoxia are the major determinants of excessive HPV in HAPE-susceptible individuals. Other hypoxia-dependent differences in ventilatory control, sympathetic nervous system activation, endothelial function, and alveolar epithelial active fluid reabsorption likely contribute additionally to HAPE susceptibility. Recent studies strongly suggest nonuniform regional hypoxic arteriolar vasoconstriction as an explanation for how HPV occurring predominantly at the arteriolar level causes leakage. In areas of high blood flow due to lesser HPV, edema develops due to pressures that exceed the dynamic and structural capacity of the alveolar capillary barrier to maintain normal fluid balance. This article will review the pathophysiology of the vasculature, alveolar epithelium, innervation, immune response, and genetics of the lung at high altitude, as well as therapeutic and prophylactic strategies to reduce the morbidity and mortality of HAPE.

The role of inflammatory cytokines on the aetiopathogenesis of depression

OBJECTIVE

The primary focus of this review is to provide an overview of the role of inflammation in the development of depression. The article will describe how inflammatory cytokines contribute to depression via action on three major pathways in the brain: the neuroendocrine; neurotransmitter depletion; and neuroprogression pathways.

METHODS

An online literature search was carried out in July 2012. Original articles and reviews were selected if they discussed the role of inflammation on the development of depression.

RESULTS

There is a large body of current research on the role of inflammatory cytokines on the development of depression. Cytokines have been found to interact with different pathways in the brain, and may contribute to the development of depression. Cytokines cause hypercortisolaemia by dysregulation of the hypothalamic-pituitary-adrenal axis directly by activating it and indirectly by modifying glucocorticoid receptor sensitivity to cortisol leading to cortisol hypersecretion. Cytokines deplete central synaptic serotonin levels by reducing its synthesis and increasing its reuptake. They may also deplete neurotrophic factors which are believed to play a neuroprotective role against depression. Cytokines activate cellular cascades that cause excitotoxicity and apoptosis and inhibit neurogenesis in the hippocampus.

CONCLUSION

There is a growing body of correlative studies that suggest inflammatory cytokines may be a central factor that can affect multiple neuronal pathways and have an additive effect on the development of depression. However, the fact that not all people with inflammatory conditions suffer from depression suggests that depression is not purely a result of elevated inflammatory cytokines. Depression may be a result of a complex pathology that remains an area of growing interest and importance.

Effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation

Background

Travel to mountain areas is popular. However, the effects of acute exposure to moderate altitude on the cardiovascular system and metabolism are largely unknown.

Objectives

To investigate the effects of acute exposure to moderate altitude on vascular function, metabolism and systemic inflammation.

Methods

In 51 healthy male subjects with a mean (SD) age of 26.9 (9.3) years, oxygen saturation, blood pressure, heart rate, arterial stiffness, lipid profiles, low density lipoprotein (LDL) particle size, insulin resistance (HOMA-index), highly-sensitive C-reactive protein and pro-inflammatory cytokines were measured at 490 m (Zurich) and during two days at 2590 m, (Davos Jakobshorn, Switzerland) in randomized order. The largest differences in outcomes between the two altitudes are reported.

Results

Mean (SD) oxygen saturation was significantly lower at 2590 m, 91.0 (2.0)%, compared to 490 m, 96.0 (1.0)%, p<0.001. Mean blood pressure (mean difference +4.8 mmHg, p<0.001) and heart rate (mean difference +3.3 bpm, p<0.001) were significantly higher at 2590 m, compared to 490 m, but this was not associated with increased arterial stiffness. At 2590 m, lipid profiles improved (median difference triglycerides −0.14 mmol/l, p = 0.012, HDL +0.08 mmol/l, p<0.001, total cholesterol/HDL-ratio −0.25, p = 0.001), LDL particle size increased (median difference +0.45 nm, p = 0.048) and hsCRP decreased (median difference −0.18 mg/l, p = 0.024) compared to 490 m. No significant change in pro-inflammatory cytokines or insulin resistance was observed upon ascent to 2590 m.

Conclusions

Short-term stay at moderate altitude is associated with increased blood pressure and heart rate likely due to augmented sympathetic activity. Exposure to moderate altitude improves the lipid profile and systemic inflammation, but seems to have no significant effect on glucose metabolism.

Trial Registration

ClinicalTrials.gov NCT01130948

Correlations of inflammatory biomarkers with the onset and prognosis of idiopathic sudden sensorineural hearing loss

HYPOTHESIS

We investigated whether inflammatory biomarkers and stress are involved in the pathophysiology of idiopathic sensorineural hearing loss (ISHL).

STUDY DESIGN

Individual cohort study.

SETTING

Two tertiary centers.

PATIENTS

Forty-three ISHL and 10 non-ISHL patients seen in our ENT departments from 2004 to 2010 within a week from the onset of new symptoms and without steroid administration before visiting our departments.

INTERVENTION

Multiple audiologic evaluations, blood tests including leukocyte counts, natural killer cell activity (NKCA), interleukin 6 (IL-6), tumor necrosis factor, high-sensitivity CRP (hCRP), and the General Health Questionnaire were used to evaluate the systemic stress and inflammatory response.

MAIN OUTCOME MEASURES

Correlations between biomarkers and ISHL severity and prognosis were evaluated by statistical analysis.

RESULTS

In the ISHL patients, a neutrophil count above the reference range was associated with severe hearing loss and poor prognosis, and was accompanied by low NKCA and high IL-6. In the non-ISHL patients, these associations were not present. The abnormal neutrophil count was independent of preexisting vascular diseases. The abnormal counts responded to treatment and decreased into the reference range.

CONCLUSION

Neutrophil counts above the reference range of a facility will be a useful indicator of poor prognosis of ISHL. Synchronism of different types of NF-κB activation pathways could be required to cause severe ISHL. An NKCA decrease, an acute neutrophil count increase, and an IL-6 increase can induce NF-κB activation in the cochlea and cause severe ISHL. Further epidemiologic surveys should be conducted to evaluate whether stressful life events increase the risk of severe ISHL onset.

Stress-evoked sterile inflammation, danger associated molecular patterns (DAMPs), microbial associated molecular patterns (MAMPs) and the inflammasome

Since the inception of the field of psychoneuroimmunolology research, there has been an appreciation that the physiological response to stressors includes modulation of immune function. Investigators initially focused on the effect of stress on cellular migration and immunosuppression and the resultant decreases in tumor surveillance, anti-viral T cell immunity and antigen-specific antibody responses. More recently, it has become clear that exposure to stressors also potentiate innate immune processes. Stressor exposure, for example, can change the activation status of myeloid lineage cells such as monocytes, macrophages, neutrophils, and microglia, leading to a primed state. In addition, stressor exposure increases the synthesis and release of a vast cadre' of inflammatory proteins both in the blood and within tissues (i.e., spleen, liver, adipose, vasculature and brain). The mechanisms for stress-evoked innate immune 'arousal' remain unknown. The goals of this presidential address are the following: (1) offer a personalized, brief overview of stress and immunity with a focus on 'aroused' innate immunity; (2) describe sterile inflammatory processes and the role of the inflammasome; and (3) suggest that these same processes likely contribute to primed myeloid cells and inflammatory protein responses (systemic and tissue) produced by stress in the absence of pathogens.

Contribution of α - and β -Adrenergic Mechanisms to the Development of Pulmonary Edema

Endogenous or exogenous catecholamines can induce pulmonary edema (PE). This may occur in human pathologic conditions such as in pheochromocytoma or in neurogenic pulmonary edema (NPE) but can also be provoked after experimental administration of adrenergic agonists. PE can result from stimulation with different types of adrenergic stimulation. With α-adrenergic treatment, it develops more rapidly, is more severe with abundant protein-rich fluid in the alveolar space, and is accompanied by strong generalized inflammation in the lung. Similar detrimental effects of α-adrenergic stimulation have repeatedly been described and are considered to play a pivotal role in NPE or in PE in patients with pheochromocytoma. Although β-adrenergic agonists have often been reported to prevent or attenuate PE by enhancing alveolar fluid clearance, PE may also be induced by β-adrenergic treatment as can be observed in tocolysis. In experimental models, infusion of β-adrenergic agonists induces less severe PE than α-adrenergic stimulation. The present paper addresses the current understanding of the possible contribution of α- and β-adrenergic pathways to the development of PE.

Psychoneuroimmunology meets neuropsychopharmacology: translational implications of the impact of inflammation on behavior

The potential contribution of chronic inflammation to the development of neuropsychiatric disorders such as major depression has received increasing attention. Elevated biomarkers of inflammation, including inflammatory cytokines and acute-phase proteins, have been found in depressed patients, and administration of inflammatory stimuli has been associated with the development of depressive symptoms. Data also have demonstrated that inflammatory cytokines can interact with multiple pathways known to be involved in the development of depression, including monoamine metabolism, neuroendocrine function, synaptic plasticity, and neurocircuits relevant to mood regulation. Further understanding of mechanisms by which cytokines alter behavior have revealed a host of pharmacologic targets that may be unique to the impact of inflammation on behavior and may be especially relevant to the treatment and prevention of depression in patients with evidence of increased inflammation. Such targets include the inflammatory signaling pathways cyclooxygenase, p38 mitogen-activated protein kinase, and nuclear factor-κB, as well as the metabolic enzyme, indoleamine-2,3-dioxygenase, which breaks down tryptophan into kynurenine. Other targets include the cytokines themselves in addition to chemokines, which attract inflammatory cells from the periphery to the brain. Psychosocial stress, diet, obesity, a leaky gut, and an imbalance between regulatory and pro-inflammatory T cells also contribute to inflammation and may serve as a focus for preventative strategies relevant to both the development of depression and its recurrence. Taken together, identification of mechanisms by which cytokines influence behavior may reveal a panoply of personalized treatment options that target the unique contributions of the immune system to depression.

Plasma adipokine and hormone changes in mountaineers on ascent to 5300 meters

OBJECTIVE

The current study evaluated multiple metabolic and inflammatory hormone responses in recreational climbers (7 men and 3 women, age 26-49 years) over 9 days. In particular, acylation-stimulating protein (ASP), which influences fat storage in adipose tissue, has not been measured at high altitude.

METHODS

Serial measurements were taken at sea level (SL), or 353 m, on day 0, 4000 m on day 3, 4750 m on day 6, and 5300 m on day 9 of the expedition.

RESULTS

Body mass index (BMI) decreased upon ascent to 5300 m from SL (SL 23.2 ± 1.5 kg/m(2); 4000 m 23.2 ± 1.4 kg/m(2); 4750 m 22.9 ± 1.3 kg/m(2); 5300 m 22.3 ± 1.2 kg/m(2); P<.001). Similarly, plasma non-esterified fatty acids and triglycerides increased, while HDL cholesterol decreased (P<.05 to <.001) from SL to 5300 m. Acylation-stimulating protein (SL 42.2 ± 40.2 nm; 4000 m 117.0 ± 69.6 nm; 4750 m 107.9 ± 44.5 nm; 5300 m 82.2 ± 20.2 nm; P=.019) and adiponectin (SL 10.4 ± 6.5 ng/mL, 4000 m 13.9 ± 8.5 ng/mL, 4750 m 18.3 ± 8.3 ng/mL, 5300 m 14.7 ± 8.0 ng/mL; P=.015) increased, as did insulin and Interleukin-6 (IL-6) levels (up to 71% and 168%, respectively; P<.05) with no change in leptin, complement C3 (C3), high sensitivity C-reactive protein (hsCRP) or cortisol levels throughout the mountain ascent from SL to 5300 m.

CONCLUSION

Acylation-stimulating protein and adiponectin are increased during a 9-day period of high altitude (SL to 5300 m) exposure despite weight loss in healthy mountaineers.

High-Altitude Pulmonary Edema

High-altitude pulmonary edema (HAPE) is an uncommon form of pulmonary edema that occurs in healthy individuals within a few days of arrival at altitudes above 2,500–3,000 m. The crucial pathophysiology is an excessive hypoxia-mediated rise in pulmonary vascular resistance (PVR) or hypoxic pulmonary vasoconstriction (HPV) leading to increased microvascular hydrostatic pressures despite normal left atrial pressure. The resultant hydrostatic stress can cause both dynamic changes in the permeability of the alveolar capillary barrier and mechanical damage leading to leakage of large proteins and erythrocytes into the alveolar space in the absence of inflammation. Bronchoalveolar lavage (BAL) and pulmonary artery (PA) and microvascular pressure measurements in humans confirm that high capillary pressure induces a high-permeability non-inflammatory-type lung edema; a concept termed “capillary stress failure.” Measurements of endothelin and nitric oxide (NO) in exhaled air, NO metabolites in BAL fluid, and NO-dependent endothelial function in the systemic circulation all point to reduced NO availability and increased endothelin in hypoxia as a major cause of the excessive hypoxic PA pressure rise in HAPE-susceptible individuals. Other hypoxia-dependent differences in ventilatory control, sympathetic nervous system activation, endothelial function, and alveolar epithelial sodium and water reabsorption likely contribute additionally to the phenotype of HAPE susceptibility. Recent studies using magnetic resonance imaging in humans strongly suggest nonuniform regional hypoxic arteriolar vasoconstriction as an explanation for how HPV occurring predominantly at the arteriolar level can cause leakage. This compelling but not yet fully proven mechanism predicts that in areas of high blood flow due to lesser vasoconstriction edema will develop owing to pressures that exceed the structural and dynamic capacity of the alveolar capillary barrier to maintain normal alveolar fluid balance. Numerous strategies aimed at lowering HPV and possibly enhancing active alveolar fluid reabsorption are effective in preventing and treating HAPE. Much has been learned about HAPE in the past four decades such that what was once a mysterious alpine malady is now a well-characterized and preventable lung disease. This chapter will relate the history, pathophysiology, and treatment of HAPE, using it not only to illuminate the condition, but also for the broader lessons it offers in understanding pulmonary vascular regulation and lung fluid balance.

Do cytokines contribute to the Andean-associated protection from reduced fetal growth at high altitude?

Pro- versus anti-inflammatory cytokine balance is important for successful pregnancy. Chronic hypoxia alters cytokine levels and increases the frequency of fetal growth restriction (FGR). Multigenerational Andean (AND) versus shorter duration European (EUR) high-altitude (HA) residents are protected from altitude-associated FGR. To address whether ancestry group differences in cytokine levels were involved, we conducted serial studies in 56 low-altitude ([LA]; 400 m; n = 29 AND and n = 27 EUR) and 42 HA residents (3600-4100 m; n = 19 ANDs and n = 23 EURs). Pregnancy raised pro- (interleukin 1β [IL-1β]) and anti- (IL-10) inflammatory cytokines and HA lowered IL-6 and tumor necrosis factor-α (TNF-α) near term. There were no ancestry group differences in cytokine levels at any time, but HA reduced IL-1β in ANDs only near term. Higher IL-1β levels correlated with uterine artery (UA) blood flow at 20 weeks in ANDs at HA, suggesting that IL-1β may play a role in AND protection from altitude-associated reductions in fetal growth.

The concept of depression as a dysfunction of the immune system

Chronic stress, by initiating changes in the hypothalamic-pituitary-adrenal axis and the immune system, acts as a trigger for anxiety and depression. Both experimental and clinical evidence shows that a rise in the concentrations of proinflammatory cytokines and glucocorticoids, as occurs in chronically stressful situations and in depression, contribute to the behavioural changes associated with depression.A defect in serotonergic function is associated with hypercortisolaemia and the increase in proinflammatory cytokines that accompany depression. Glucocorticoids and proinflammatory cytokines enhance the conversion of tryptophan to kynurenine. In addition to the resulting decrease in the synthesis of brain serotonin, this leads to the formation of neurotoxins such as the glutamate agonist quinolinic acid and contributes to the increase in apoptosis of astrocytes, oligodendroglia and neurons.The importance of the inflammation hypothesis of depression lies in raising the possibility that psychotropic drugs that have a central anti-inflammatory action might provide a new generation of antidepressants.

The effect of high-altitude on human skeletal muscle energetics: P-MRS results from the Caudwell Xtreme Everest expedition

Many disease states are associated with regional or systemic hypoxia. The study of healthy individuals exposed to high-altitude hypoxia offers a way to explore hypoxic adaptation without the confounding effects of disease and therapeutic interventions. Using ³¹P magnetic resonance spectroscopy and imaging, we investigated skeletal muscle energetics and morphology after exposure to hypobaric hypoxia in seven altitude-naïve subjects (trekkers) and seven experienced climbers. The trekkers ascended to 5300 m while the climbers ascended above 7950 m. Before the study, climbers had better mitochondrial function (evidenced by shorter phosphocreatine recovery halftime) than trekkers: 16±1 vs. 22±2 s (mean ± SE, p<0.01). Climbers had higher resting [Pi] than trekkers before the expedition and resting [Pi] was raised across both groups on their return (PRE: 2.6±0.2 vs. POST: 3.0±0.2 mM, p<0.05). There was significant muscle atrophy post-CXE (PRE: 4.7±0.2 vs. POST: 4.5±0.2 cm², p<0.05), yet exercising metabolites were unchanged. These results suggest that, in response to high altitude hypoxia, skeletal muscle function is maintained in humans, despite significant atrophy.