Therapeutic effects of melatonin on heatstroke-induced multiple organ dysfunction syndrome in rats

Signaling pathways in skin cancers and the protective functions of melatonin

Melatonin, a hormone primarily synthesized in the pineal gland, has an essential role in the regulation of various physiological processes, such as the sleep-wake cycle, immune function, and antioxidative responses. Emerging evidence suggests that melatonin also exerts significant protective effects against skin cancers, particularly melanoma and non-melanoma skin cancers. This review aims to provide a comprehensive overview of melatonin's multifaceted mechanisms of action in preventing and treating skin cancers, focusing on its antioxidant, photoprotective, and radioprotective properties. Melatonin's capability to modulate skin cancer's related key signaling pathways underscores its complex yet potent anticancer mechanisms. Furthermore, synergistic effects between melatonin and conventional oncology treatments, such as radiotherapy, chemotherapy, and targeted therapies, hold promise for improving treatment outcomes while mitigating adverse effects. However, while melatonin shows great potential as an adjunct in oncology treatment regimens, further research is needed to optimize its clinical applications and fully understand its safety profile and potential side effects. Overall, elucidating melatonin's role in skin cancer prevention and treatment represents a promising avenue for advancing cancer therapeutics and improving patient outcomes.

Single-cell sequencing reveals the same heterogeneity of neutrophils in heatstroke-induced lung and liver injury

Heatstroke (HS) is typically considered a sepsis-like syndrome caused by hyperthermia, often accompanied by multiple organ dysfunctions (MODS). To explore the mechanisms of MODS, we established a mouse model of HS by exposing mice to a hyperthermic and high-humidity environment. Then, we utilized single-cell RNA sequencing (scRNA-seq) to depict the cellular landscape of HS mice lung tissue and liver tissue. We found that the enhancement of neutrophil infiltration mediated by the "Cxcr2-Cxcl2″ receptor-ligand pair is a prominent feature of HS-induced lung injury. By effectively suppressing the recruitment of neutrophils in HS-induced lung injury, the application of Cxcr2 inhibitor held positive implications for improving HS-induced lung injury. In addition to the chemotactic effect of immune cells on neutrophils, we identified a subcluster of fibroblasts labeled as Col14a1+, which possessed notable chemotactic factor-secretion characteristics and likely exerted a role in the early stages of neutrophil infiltration. Furthermore, our study unveiled significant heterogeneity among neutrophils within the HS-induced lung injury. Particularly, Cd177 + neutrophils exhibited a dominant presence, characterized by heightened pro-inflammatory responses and oxidative stress. In heatstroke-induced liver injury, neutrophils exhibited similar heterogeneous characteristics. Cd177 + neutrophils exhibited an enhanced ability to produce neutrophil extracellular traps (NETs) while lowering the levels of NETs can significantly improve heatstroke-induced lung and liver injury. Additionally, our study identified Cebpe as a key transcriptional regulatory factor in Cd177 + neutrophil differentiation. Knockdown of the expression of Cebpe can suppress the Cd177 + neutrophil differentiation and decrease the expression levels of NETs. Our research indicated a common heterogeneity in neutrophils during MODS in HS. Cd177 + neutrophils contributed to organ damage in HS, and Cebpe may serve as a crucial intervention target in the treatment of HS.

Heatstroke-Induced Inflammatory Response and Therapeutic Biomarkers

In recent years, heatstroke has become one of the most dangerous illnesses associated with hyperthermia. Hyperthermia is described as an increased body temperature, where there is more heat accrual than dissipation, which happens during environmental heat stress conditions or exhaustive exercise and subsequently leads to heatstroke. Heatstroke is characterized as a dysfunction of the central nervous system (CNS), associated with neuroinflammation, including utmost hyperthermia, which eventually leads to multiorgan failure. Heatstroke-related fatalities have rapidly increased in the recent past; however, there is still a gap in the understanding of heatstroke and associated outcomes during heatstroke. Especially of note, early diagnosis of heatstroke-related complications is one of the important aspects that need to be addressed. This article reviewed current knowledge about heatstroke and associated inflammatory responses, including neuroinflammation and other clinical complications. Using molecular dynamics simulation analysis of triose phosphate isomerase (a housekeeping enzyme) at different temperatures, we demonstrated how protein structures, and thus their functions, can be varied with temperature increases. Additionally, we discussed therapeutically relevant biomarkers of heatstroke which might be helpful in the early detection of heatstroke possibilities and candidate drug targets to control or minimize heatstroke events.

Heat stroke: Pathogenesis, diagnosis, and current treatment

Recently, the incidence of heat-related illnesses has exhibited a steadily upward trend, which is closely associated with several environmental factors such as climate change and air pollution. The progression of heat-related illnesses is a continuous process and can progress to the terminal period when it transforms into heat stroke, the most severe form. Heat stroke is markedly by a core body temperature above 40°C and central nervous system dysfunction. Current knowledge suggests that the pathogenesis of heat stroke is complex and varied, including inflammatory response, oxidative stress, cell death, and coagulation dysfunction. This review consolidated recent research progress on the pathophysiology and pathogenesis of heat stroke, with a focus on the related molecular mechanisms. In addition, we reviewed common strategies and sorted out the drugs in various preclinical stages for heat stroke, aiming to offer a comprehensive research roadmap for more in-depth researches into the mechanisms of heat stroke and the reduction in the mortality of heat stroke in the future.

New Perspectives on the Role and Therapeutic Potential of Melatonin in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the leading cause of death and disability worldwide. It is essential to develop novel interventions to prevent/delay CVDs by targeting their fundamental cellular and molecular processes. Melatonin is a small indole molecule acting both as a hormone of the pineal gland and as a local regulator molecule in various tissues. It has multiple features that may contribute to its cardiovascular protection. Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiological barriers. Additionally, this indoleamine also serves as a safe exogenous therapeutic agent. Increasing evidence has demonstrated the beneficial effects of melatonin in preventing and improving cardiovascular risk factors. Exogenous administration of melatonin, as a result of its antioxidant and anti-inflammatory properties, has been reported to decrease blood pressure, protect against atherosclerosis, attenuate molecular and cellular damage resulting from cardiac ischemia/reperfusion, and improve the prognosis of myocardial infarction and heart failure. This review aims to summarize the beneficial effects of melatonin against these conditions, the possible protective mechanisms of melatonin, and its potential clinical applicability in CVDs.

Melatonin alleviates lung injury in H1N1-infected mice by mast cell inactivation and cytokine storm suppression

Influenza A virus (IAV) H1N1 infection is a constant threat to human health and it remains so due to the lack of an effective treatment. Since melatonin is a potent antioxidant and anti-inflammatory molecule with anti-viral action, in the present study we used melatonin to protect against H1N1 infection under in vitro and in vivo conditions. The death rate of the H1N1-infected mice was negatively associated with the nose and lung tissue local melatonin levels but not with serum melatonin concentrations. The H1N1-infected AANAT-/- melatonin-deficient mice had a significantly higher death rate than that of the WT mice and melatonin administration significantly reduced the death rate. All evidence confirmed the protective effects of melatonin against H1N1 infection. Further study identified that the mast cells were the primary targets of melatonin action, i.e., melatonin suppresses the mast cell activation caused by H1N1 infection. The molecular mechanisms involved melatonin down-regulation of gene expression for the HIF-1 pathway and inhibition of proinflammatory cytokine release from mast cells; this resulted in a reduction in the migration and activation of the macrophages and neutrophils in the lung tissue. This pathway was mediated by melatonin receptor 2 (MT2) since the MT2 specific antagonist 4P-PDOT significantly blocked the effects of melatonin on mast cell activation. Via targeting mast cells, melatonin suppressed apoptosis of alveolar epithelial cells and the lung injury caused by H1N1 infection. The findings provide a novel mechanism to protect against the H1N1-induced pulmonary injury, which may better facilitate the progress of new strategies to fight H1N1 infection or other IAV viral infections.

Melatonin-Microbiome Two-Sided Interaction in Dysbiosis-Associated Conditions

Melatonin is a pineal indolamine, allegedly known as a circadian rhythm regulator, and an antioxidative and immunomodulatory molecule. In both experimental and clinical trials, melatonin has been shown to have positive effects in various pathologies, as a modulator of important biochemical pathways including inflammation, oxidative stress, cell injury, apoptosis, and energy metabolism. The gut represents one of melatonin's most abundant extra pineal sources, with a 400-times-higher concentration than the pineal gland. The importance of the gut microbial community-namely, the gut microbiota, in multiple critical functions of the organism- has been extensively studied throughout time, and its imbalance has been associated with a variety of human pathologies. Recent studies highlight a possible gut microbiota-modulating role of melatonin, with possible implications for the treatment of these pathologies. Consequently, melatonin might prove to be a valuable and versatile therapeutic agent, as it is well known to elicit positive functions on the microbiota in many dysbiosis-associated conditions, such as inflammatory bowel disease, chronodisruption-induced dysbiosis, obesity, and neuropsychiatric disorders. This review intends to lay the basis for a deeper comprehension of melatonin, gut microbiota, and host-health subtle interactions.

Night shift hormone: How does melatonin affect depression?

Melatonin is the main hormone secreted by the pineal gland that modulates the circadian rhythm and mood. Previous studies have shown the therapeutic effects of melatonin, or its important analogue, agomelatine, on depression. In this review study, we aimed to discuss the potential mechanisms of melatonin involved in the treatment of depression. It was noted that disrupted circadian rhythm can lead to depressive state, and melatonin via regulating circadian rhythm shows a therapeutic effect. It was also noted that melatonin induces antidepressant effects via promoting antioxidant system and neurogenesis, and suppressing oxidative stress, neuroinflammation, and apoptosis. The interaction effect between melatonin or agomelatine and serotonergic signaling has a significant effect on depression. It was noted that the psychotropic effects of agomelatine are induced by the synergistic interaction between melatonin and 5-HT_2C receptors. Agomelatine also interacts with glutamatergic signaling in brain regions involved in regulating mood and circadian rhythm. Interestingly, it was concluded that melatonin exerts both pro- and anti-inflammatory effects, depending on the grade of inflammation. It was suggested that synergistic interaction between melatonin and 5-HT_2C receptors may be able to induce therapeutic effects on other psychiatric disorders. Furthermore, dualistic role of melatonin in regulating inflammation is an important point that can be examined at different levels of inflammation in animal models of depression.

Assessment of Stress Salivary Markers, Perceived Stress, and Shift Work in a Cohort of Fishermen: A Preliminary Work

Due to work-related stress, today, work itself represents a daily challenge that must be faced in many occupations. While, in the past, the scientific community has focused on the helping professions, since, an increasing number of professions have since been investigated. Therefore, different approaches exist in order to assess this disorder, representing a scientific field wherein biological and psychological dimensions both need to be evaluated. In this paper, we consider three biological salivary markers: interleukin 1 beta (IL-1β), cortisol, and melatonin. The choice derives from recent contributions to the literature in which the interplay between these markers has been verified. Briefly, such interplay could explain how the central nervous, endocrine, and immune systems communicate with each other, supporting a holistic concept of person. In 30 marine fishermen from the Apulia region of Italy, perceived stress was measured using the Professional Stress Scale (PSS) and sleep disturbances were assessed through the Pittsburgh Sleep Quality Index (PSQI). Salivary markers were collected at 8:00 a.m. and 2:00 p.m. Those subjects reporting sleep disturbance and having altered scores in two PSS subclasses, home-work conflict and self-esteem, presented inverted salivary melatonin and cortisol nictemeral rhythms (with regard to melatonin levels at 8:00 a.m., those workers reporting values higher than the median showed 64.1% versus 48.6% home-work conflict with respect to cortisol levels, subjects having an inverted circadian rhythm showed 69.9% versus 52.5% home-work conflict, and these values resulted 47.7% versus 25.3% when the self-esteem was considered). As regards melatonin, PSQI score is statistically different in the two groups of subjects as identified by median melatonin at 8:00 a.m.; specifically, the subjects who had mean values higher than the median shared higher PSQI scores (10.8 versus 9.8). The same subjects reported more frequent home-work conflict and more sleep disorders. We found a negative correlation between IL-1β at 8:00 a.m. and Cortdiff (the difference between cortisol at 8:00 a.m.-cortisol at 2:00 p.m.), and that high IL-1β at 8:00 a.m. was associated with low Cortdiff. Based on our results we would like to propose this approach in health surveillance, in order to prevent mental and/or physical disorders, however our study is surely preliminary. The interesting perspectives and hypotheses cited in this paper, in which the roles of IL-1β and norepinephrine appear central and important, could remain hypothetical if not supported by more robust observation in order to produce, truly, new knowledge. In the future we will deepen this study with a larger sample, and if these results will be confirmed, this approach could allow preventing, not only mental and physical disorders, but also immuno-mediated diseases, and, perhaps, cancer.

Associations between Melatonin, Neuroinflammation, and Brain Alterations in Depression

Pro-inflammatory systemic conditions that can cause neuroinflammation and subsequent alterations in brain regions involved in emotional regulation have been suggested as an underlying mechanism for the pathophysiology of major depressive disorder (MDD). A prominent feature of MDD is disruption of circadian rhythms, of which melatonin is considered a key moderator, and alterations in the melatonin system have been implicated in MDD. Melatonin is involved in immune system regulation and has been shown to possess anti-inflammatory properties in inflammatory conditions, through both immunological and non-immunological actions. Melatonin has been suggested as a highly cytoprotective and neuroprotective substance and shown to stimulate all stages of neuroplasticity in animal models. The ability of melatonin to suppress inflammatory responses through immunological and non-immunological actions, thus influencing neuroinflammation and neurotoxicity, along with subsequent alterations in brain regions that are implicated in depression, can be demonstrated by the antidepressant-like effects of melatonin. Further studies that investigate the associations between melatonin, immune markers, and alterations in the brain structure and function in patients with depression could identify potential MDD biomarkers.

Ex vivo approach supports both direct and indirect actions of melatonin on immunity in pike-perch Sander lucioperca

The melatonin hormone, which is a multifunctional molecule in vertebrates, has been shown to exert complex actions on the immune system of mammals. In teleosts, the immunomodulatory capacity of this hormone has seldom been investigated. In the present experiment, we exposed ex vivo spleen and head kidney tissues of pike-perch to melatonin (Mel) and cortisol (Cort). We applied three concentrations of both hormones, alone and in combination, namely (1) Mel (10, 100 or 1000 pg mL^-1) (2) Cort (50, 500 or 5000 ng mL^-1) (3) Mel + Cort (10 + 50, 100 + 500 or 1000 pg mL^-1+5000 ng mL^-1). Pure medium without Mel or Cort served as control. After 15 h of incubation, we assessed the expression of a set of immunity-related genes, including genes encoding for pro-inflammatory proteins (il-1β, cxcl8 and tnf-α), acute-phase proteins (fgl2, fth1, hepc, hp and saa1) and key factors of the adaptive immune system (fκbp4 and tcrg). Both Mel and Cort, when used alone or combined at physiological concentrations, significantly influenced immune gene expressions that may lead to a global immune stimulation. Our results support both, an indirect action of the Mel hormone on the immune system through the regulation of intermediates such as Cort, as well as a direct action on immune targets through specific receptors.

Molecular links between endocrine, nervous and immune system during chronic stress

INTRODUCTION

The stress response is different in various individuals, however, the mechanisms that could explain these distinct effects are not well known and the molecular correlates have been considered one at the time. Particular harmful conditions occur if the subject, instead to cope the stressful events, succumb to them, in this case, a cascade reaction happens that through different signaling causes a specific reaction named "sickness behaviour." The aim of this article is to review the complex relations among important molecules belonging to Central nervous system (CNS), immune system (IS), and endocrine system (ES) during the chronic stress response.

METHODS

After having verified the state of art concerning the function of cortisol, norepinephrine (NE), interleukin (IL)-1β and melatonin, we describe as they work together.

RESULTS

We propose a speculative hypothesis concerning the complex interplay of these signaling molecules during chronic stress, highlighting the role of IL-1β as main biomarker of this effects, indeed, during chronic stress its increment transforms this inflammatory signal into a nervous signal (NE), in turn, this uses the ES (melatonin and cortisol) to counterbalance again IL-1β. During cortisol resistance, a vicious loop occurs that increments all mediators, unbalancing IS, ES, and CNS networks. This IL-1β increase would occur above all when the individual succumbs to stressful events, showing the Sickness Behaviour Symptoms. IL-1β might, through melatonin and vice versa, determine sleep disorders too.

CONCLUSION

The molecular links here outlined could explain how stress plays a role in etiopathogenesis of several diseases through this complex interplay.

Heat precondition is a potential strategy to combat hepatic injury triggered by severe heat stress

AIM

Environmental heat stress alters physiological and biochemical functions which leads to multiorgan dysfunction including severe hepatic injury in animals. We hypothesize that heat preconditioning can be potential intervention in combating heat illnesses.

MAIN METHODS

Sprague Dawley rats were exposed to moderate heat stress, severe heat stress and heat preconditioning in heat simulation chamber. Mean arterial pressure, heart rate, skin and core temperature were monitored in pre and post heat exposed animals. After stress exposure, blood for hemodynamic and liver tissue for liver function tests, oxidative stress, inflammatory variables and structural studies were collected from rats. Hepatic mitochondria were isolated to study the key structural alterations and functional changes by transmission electron microscopy.

KEY FINDINGS

The effect of heat precondition shows improvement in time to attain the core temperature, weight loss, blood pressure and heart rate in rats. Results exhibited decreased levels of liver function tests, elevated levels of free radicals and inflammatory cytokines in heat exposed liver as compared with heat preconditioned animals. Expression levels of mitochondrial heat shock protein 60, superoxide dismutase 1 and uncoupling protein 1 along with activity of electron transport chain complexes I-V were examined and found to be increased in heat preconditioned as compared to heat stressed animals. Morphological studies of liver parenchyma demonstrated reduction in structural deterioration of hepatic lobules and restoration of mitochondrial structural integrity in heat preconditioned rats.

SIGNIFICANCE

Present study suggests that heat preconditioning intervention plays a crucial role in protection against heat induced hepatic injury in animals.

Melatonin down-regulates steroidal hormones, thymocyte apoptosis and inflammatory cytokines in middle-aged T. cruzi infected rats

Chagas disease, triggered by the flagellate protozoan Trypanosoma cruzi (T. cruzi) plays a potentially threat to historically non-endemic areas. Considerable evidence established that the immuno-endocrine balance could deeply influence the experimental T. cruzi progression inside the host's body. A high-resolution multiple reaction monitoring approach (MRM^HR) was used to study the influence of melatonin on adrenal and plasma steroidal hormones profile of T. cruzi infected Wistar rats. Young (5 weeks) and middle-aged (18 months) male Wistar rats received melatonin (5 mg/Kg, orally) during the acute Chagas disease. Corticosterone, 11-dehydrocorticosterone (11-DHC), cortisol, cortisone, aldosterone, progesterone and melatonin concentration were evaluated. Interleukin-1 alpha and β (IL-1α and β), IL-6 and transforming growth factor beta (TGF-β) were also analyzed. Our results revealed an increased production of corticosterone, cortisone, cortisol and aldosterone in middle-aged control animals, thus confirming the aging effects on the steroidal hormone profile. Serum melatonin levels were reduced with age and predominantly higher in young and middle-aged infected rats. Melatonin treatment reduced the corticosterone, 11-DHC, cortisol, cortisone, aldosterone and progesterone in response to T. cruzi infection. Decreased IL-1 α and β concentrations were also found in melatonin treated middle-aged infected animals. Melatonin treated middle-aged control rats displayed reduced concentrations of TGF-β. Melatonin levels were significantly higher in all middle-aged rats treated animals. Reduced percentages of early and late thymocyte apoptosis was found for young and middle-aged melatonin supplemented rats. Finally, our results show a link between the therapeutic and biological effects of melatonin controlling steroidal hormones pathways as well as inflammatory mediators.

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Melatonin acts on the regulation of steroid hormones, apoptosis and cytokine signaling during acute T. cruzi infection;

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Middle-aged control rats have higher production of corticosterone, cortisone, cortisol and aldosterone;

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Melatonin treated middle-aged infected rats displayed reduced concentrations of IL-1 α and β;

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Melatonin levels were significantly higher in all middle-aged rats treated animals;

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Reduced percentages of early and late thymocyte apoptosis was found for young and middle-aged melatonin supplemented rats.

Astaxanthin supplementation impacts the cellular HSP expression profile during passive heating

Astaxanthin is a powerful carotenoid antioxidant prevalent in marine organisms and approved as a food supplement. Recent studies have demonstrated Astaxanthin's beneficial attributes in various health states. Following initial reports of potential heat protective properties in Astaxanthin supplemented rats, we present here results of a novel study examining the effect of Astaxanthin supplementation on the heat shock response in rats in relation to core temperature (Tc) and the ensuing physiological strain. Two hours of heat stress at 41 °C during which rats developed their thermoregulatory hyperthermic plateau resulted in progressive increases in HSP72 and HSP27 in the Astaxanthin (Oleoresin)-treated group but not in the control (Olive oil) group. Enhanced elevation in HSPs suggests that Astaxanthin supplementation may augment the cellular stress protective response to heat stress.

Dim light at night: physiological effects and ecological consequences for infectious disease

Light pollution has emerged as a pervasive component of land development over the past century. Several detrimental impacts of this anthropogenic influence have been identified in night shift workers, laboratory rodents, and a plethora of wildlife species. Circadian, or daily, patterns are interrupted by the presence of light at night and have the capacity to alter rhythmic physiological or behavioral characteristics. Indeed, biorhythm disruption can lead to metabolic, reproductive, and immunological dysfunction depending on the intensity, timing, duration, and wavelength of light exposure. Light pollution, in many forms and by many pathways, is thus apt to affect the nature of host-pathogen interactions. However, no research has yet investigated this possibility. The goal of this manuscript is to outline how dim light at night, a relevant and common form of light pollution, may affect disease dynamics by interrupting circadian rhythms and regulation of immune responses as well as opportunities for host-parasite interactions and subsequent transmission risk including spillover into humans. We close by proposing some promising interventions including alternative lighting methods or vector control efforts.

Glutamine alleviates heat stress-induced impairment of intestinal morphology, intestinal inflammatory response, and barrier integrity in broilers

The aim of this study was to investigate the protective effect of glutamine (Gln) on the intestinal morphology, intestinal inflammatory response, and barrier integrity in broilers exposed to high ambient temperature. Three-hundred-sixty 21-d-old Arbor Acres broilers (half male and half female) were randomly allocated to 4 treatment groups in a completely randomized design, each of which included 6 replicates with 15 birds per replicate, for 21 d. The 4 treatment groups were as follows: the control group, in which birds were kept in a thermoneutral room at 22 ± 1°C (no stress, NS; fed a basal diet); the heat stress group (36 ± 1°C for 10 h/d from 08:00 to 18:00 h and 22 ± 1°C for the remaining time, heat stress (HT); fed a basal diet); and heat stress + Gln group (0.5 and 1.0% Gln, respectively). Compared to the NS group, broilers in the HT group had lower villus height (P < 0.05), higher crypt depth (P < 0.05), higher D-lactic acid and diamine oxidase (DAO) activity (P < 0.05), higher soluble intercellular adhesion molecule-1 (sICAM-1) concentration (P < 0.05), higher tumor necrosis factor (TNF)-α/interleukin (IL)-10 (P < 0.05), and lower tight junction protein expression levels (P < 0.05). Compared with birds in the HT, birds in the HT + Gln group exhibited increased villus height (P < 0.05), decreased D-lactate and DAO activity (P < 0.05), decreased sICAM-1 concentration (P < 0.05), and mediate the secretion of cytokines (P < 0.05), as well as increased zonula occludens-1 (ZO-1), claudin-1, and occludin mRNA expression levels (P < 0.05). In conclusion, these results indicate that supplementation with Gln was effective in partially ameliorating the adverse effects of heat stress on intestinal barrier function in broilers by promoting epithelial cell proliferation and renewal, modifying the function of the intestinal mucosa barrier, and regulating the secretion of cytokines.

Melatonin improves quality and longevity of chronic neural recording

The chronic performance of implantable neural electrodes is hindered by inflammatory brain tissue responses, including microglia activation, glial scarring, and neuronal loss. Melatonin (MT) has shown remarkable neuroprotective and neurorestorative effects in treating central nervous system (CNS) injuries and degeneration by inhibiting caspase-1, -3, and -9 activation and mitochondrial cytochrome c release, as well as reducing oxidative stress and neuroinflammation. This study examined the effect of MT administration on the quality and longevity of neural recording from an implanted microelectrode in the visual cortex of mice for 16 weeks. MT (30 mg/kg) was administered via daily intraperitoneal injection for acute (3 days before and 14 days post-implantation) and chronic (3 days before and 16 weeks post-implantation) exposures. During the first 4 weeks, both MT groups showed significantly higher single-unit (SU) yield, signal-to-noise ratio (SNR), and amplitude compared to the vehicle control group. However, after 4 weeks of implantation, the SU yield of the acute treatment group dropped to the same level as the control group, while the chronic treatment group maintained significantly higher SU yield compared to both acute (week 5-16) and control (week 0-16) mice. Histological studies revealed a significant increase in neuronal viability and decrease in neuronal apoptosis around the implanted electrode at week 16 in the chronic group in comparison to control and acute subjects, which is correlated with reduced oxidative stress and increased number of pro-regeneration arginase-1 positive microglia cells. These results demonstrate the potent effect of MT treatment in maintaining a high-quality electrode-tissue interface and suggest that MT promotes neuroprotection possibly through its anti-apoptotic, anti-inflammatory, and anti-oxidative properties.

Adjuvant rhubarb alleviates organs dysfunction and inhibits inflammation in heat stroke

The aim of the present study was to investigate the effects of adjuvant rhubarb on the recovery of patients with heat stroke. A total of 85 patients with heat stroke were randomly assigned to two treatment groups: One group receiving conventional treatment for heat stroke (conventional group) and one group receiving rhubarb supplement in addition to conventional treatment (rhubarb group). Liver and kidney function parameters, Acute Physiology and Chronic Health Evaluation (APACHE) II scores, plasma interleukin-6 (IL-6), procalcitonin (PCT), C-reactive protein (CRP) levels and venous white blood cell count (WBC) were analyzed. The length of stay in the intensive care units (ICUs) and hospital were recorded. Kaplan-Meier curves were drawn to determine the 30-day survival of the patients. The results indicated that rhubarb supplementation significantly reduced the WBC, as well as CRP, PCT and IL-6 levels at treatment days 3-5. Furthermore, rhubarb intake was observed to limit heat stroke-induced damage to liver and kidney function by decreasing the abnormally high levels of plasma aspartate aminotransferase, alanine aminotransferase and creatinine. Finally, patients in the rhubarb group had shorter ICU and hospital stays as well as a lower APACHE II score than those in the conventional group. However, no significant difference in the 30-day mortality rate was observed between the two groups. In conclusion, rhubarb intake provided a significant benefit for patients with heat stroke by inhibiting systemic inflammation and mitigating liver and kidney injury.

Moderate glucose supply reduces hemolysis during systemic inflammation

Background

Systemic inflammation alters energy metabolism. A sufficient glucose level, however, is most important for erythrocytes, since erythrocytes rely on glucose as sole source of energy. Damage to erythrocytes leads to hemolysis. Both disorders of glucose metabolism and hemolysis are associated with an increased risk of death. The objective of the study was to investigate the impact of intravenous glucose on hemolysis during systemic inflammation.

Materials and methods

Systemic inflammation was accomplished in male Wistar rats by continuous lipopolysaccharide (LPS) infusion (1 mg LPS/kg and h, 300 min). Sham control group rats received Ringer’s solution. Glucose was supplied moderately (70 mg glucose/kg and h) or excessively (210 mg glucose/kg and h) during systemic inflammation. Vital parameters (eg, systemic blood pressure) as well as blood and plasma parameters (eg, concentrations of glucose, lactate and cell-free hemoglobin, and activity of lactate dehydrogenase) were measured hourly. Clot formation was analyzed by thromboelastometry.

Results

Continuous infusion of LPS led to a so-called post-aggression syndrome with disturbed electrolyte homeostasis (hypocalcemia, hyperkalemia, and hypernatremia), changes in hemodynamics (tachycardia and hypertension), and a catabolic metabolism (early hyperglycemia, late hypoglycemia, and lactate formation). It induced severe tissue injury (significant increases in plasma concentrations of transaminases and lactate dehydrogenase), alterations in blood coagulation (disturbed clot formation), and massive hemolysis. Both moderate and excessive glucose supply reduced LPS-induced increase in systemic blood pressure. Excessive but not moderate glucose supply increased blood glucose level and enhanced tissue injury. Glucose supply did not reduce LPS-induced alterations in coagulation, but significantly reduced hemolysis induced by LPS.

Conclusion

Intravenous glucose infusion can diminish LPS-related changes in hemodynamics, glucose metabolism, and, more interestingly, LPS-induced hemolysis. Since cell-free hemoglobin is known to be a predictor for patient’s survival, a reduction of hemolysis by 35% only by the addition of a small amount of glucose is another step to minimize mortality during systemic inflammation.

Melatonin provides protection against heat stroke-induced myocardial injury in male rats

OBJECTIVES

This study aimed to investigate the cardioprotective effects of melatonin on heat stroke (HS) induced acute myocardial infarction in rats and to explore the underlying mechanisms.

METHODS

Myocardial injury was induced by subjecting the anaesthetized rats to a high ambient temperature of 43°C for 70 min. Such a high ambient temperature caused hyperthermia, hypotension and myocardial injury in rats. Rats were treated with melatonin (3 mg/kg) intravenously one hour before and followed by an additional dose immediately after heat stress.

KEY FINDINGS

At the onset of HS, animals displayed myocardial injury evidenced by increased levels of cardiac damage indicators (e.g. total lactate dehydrogenase, cardiac troponin I and creatine kinase-MB), increased cardiac damage scores and suppressed left ventricular performance. Animals with HS also had increased cardiac oxidative stress evidenced by increased levels of lipid peroxidation (e.g. increased thiobarbituric acid reactive substances) and decreased levels of antioxidant enzymes (e.g. superoxide dismutase, catalase and reduced glutathione) and activated inflammation (e.g. increased levels of interleukin-6 and tumour necrosis factor-α). Pretreatment with melatonin significantly reversed the HS-induced myocardial injury, cardiac oxidative stress and cardiac inflammation.

CONCLUSIONS

Melatonin may protect against HS-induced myocardial injury in male rats by mitigating oxidative stress and inflammation.

Expressions of chemokines and their receptors in the brain after heat stroke-induced cortical damage

Despite growing evidence that cytokines and chemokines are expressed in humans and rats after heat stress, the cellular mechanisms underlying the effects on the brain after heatstroke (HS) are not fully understood. In this study, we observed time course changes of chemokines in rat brain tissues and elucidated what kinds of cortical cells were affected after HS. Male SD rats were anesthetized and randomly separated into two groups as follows: (a) normothermic sham and (b) HS rats. Rats were sacrificed at different time points (0, 1, 3, 6, and 12h after heat exposure, n=5 in each group) to the end of the experiment in order to extract the mRNA/proteins of cortical tissues. Cerebrospinal fluid (CSF) of sham and HS rats was also collected before sacrifice. In the HS group, an elevated body temperature (Tco>40°C) and abnormality of cortical cells (e.g., pyknotic nuclei) were observed. When compared to the sham group, expression levels of either mRNAs or proteins of chemokines and their receptors (including CXCL1, MIP2, MCP1, CXCR1, CXCR2, and CCR2) peaked at different time points after heat exposure. We also found that CXCR2 was expressed in the cortex of rat brain and was colocalized with neurons and microglia after HS. Hence, MCP1, MIP2, and CXCR2 might play important roles in the brain after HS, possibly indicating a new direction for treating HS.

Effects of Sleep Quality on Melatonin Levels and Inflammatory Response after Major Abdominal Surgery in an Intensive Care Unit

Disruption of nocturnal sleep in an intensive care unit may remarkably affect production of melatonin, which is also known to have anti-inflammatory properties. In the present study, we aimed to investigate the effect of sleep quality on melatonin levels and inflammation after surgery. Thus, we compared the patients, who were screened in the side-rooms where the lights were dimmed and noise levels were reduced, with the patients who received usual care. Preoperative and postoperative urine 6-sulphatoxymelatonin, serum interleukin-1 (IL-1), interleukin-6 (IL-6), and c-reactive protein (CRP) levels were measured and data on sleep quality was collected using the Richards–Campbell Sleep Questionnaire. Postoperative CRP and IL-6 levels were greater in the control group than in the experimental group, whereas postoperative 24 h melatonin levels were greater than preoperative levels and the difference was steeper in the experimental group in concordance with sleep quality scores. Thus, the regulation of light and noise in ICUs may help the recovery after major surgeries in patients, potentially by increasing melatonin production, which has anti-inflammatory properties.

Sodium tanshinone IIA sulfonate improves inflammation, aortic endothelial cell apoptosis, disseminated intravascular coagulation and multiple organ damage in a rat heat stroke model

The aim of the present study was to investigate the effects of sodium tanshinone IIA sulfonate (STS) on inflammatory responses, aortic endothelial cell apoptosis, disseminated intravascular coagulation (DIC) and multiple organ damage in an animal model of classic heat stroke (CHS). The rats in the heat stroke (HS) and STS-treated heat stroke (STS-HS) groups were placed into a pre-warmed animal temperature controller (ATC) at 35°C. The moment at which the rectal temperature reached 43.5°C was considered as the time of onset of HS. In the HS groups, the rats were removed from the ATC and allowed to recover at 26°C for 0, 2, 6 or 12 h. In the STS-HS groups, the rats received femoral vein injections of 5–40 mg/kg STS immediately following the onset of HS and were subsequently placed at a temperature of 26°C to recover for 6 h. In the present study, the serum levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were assessed using ELISA, and the numbers of apoptotic aortic endothelial cells were investigated using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling combined with immunofluorescence. In the HS groups, the serum levels of TNF-α, IL-1β and IL-6, as well as the numbers of apoptotic aortic endothelial cells were increased compared with the normothermic control group. Additionally, the plasma prothrombin time, activated partial thromboplastin time and D-dimer level were significantly increased in the HS group compared with the normothermic control group following recovery for 6 h. By contrast, the platelet count was decreased in the HS group compared with the normothermic control group. The serum levels of creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase were increased and histopathological damage to multiple organs was observed in the HS group following recovery for 6 h. In the STS-HS groups, cytokine levels and apoptotic aortic endothelial cell numbers were reduced compared with the HS group after 6 h recovery. STS (40 mg/kg) treatment additionally improved the serum levels of organ injury indicators and plasma indicators of coagulopathy, and prevented histopathological damage to multiple organs. These findings demonstrated that STS treatment may ameliorate multiple organ damage by attenuating inflammatory responses, aortic endothelial cell apoptosis and DIC in CHS. These results suggested that STS may hold potential as an alternative therapeutic strategy for the treatment of patients with HS.

Dexamethasone improves heat stroke-induced multiorgan dysfunction and damage in rats

Dexamethasone (DXM) is known as an immunosuppressive drug used for inflammation control. In the present study, we attempted to examine whether DXM administration could attenuate the hypercoagulable state and the overproduction of pro-inflammatory cytokines, improve arterial hypotension, cerebral ischemia and damage, and vital organ failure in a rat model of heat stroke. The results indicated that all the rats suffering from heat stroke showed high serum levels of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), accompanied with increased prothrombin time, activated partial thromboplastin time and D-D dimer, and decreased protein C. During the induction period of heat stroke, plasma levels of blood urea nitrogen (BUN), creatinine, glutamic oxaloacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT), and alkaline phosphatase (ALP), were consistently increased. High striatal levels of glycerol, glutamate, and lactate/pyruvate were simultaneously detected. On the contrary, the mean arterial pressure, plasma levels of interleukin-10 (IL-10), and local cerebral blood flow at the striatum were all decreased. Importantly, intravenous administration of DXM substantially ameliorated the circulatory dysfunction, systematic inflammation, hypercoagulable state, cerebral ischemia and damage during the induction period of heat stroke. These findings demonstrated that DXM may be an alternative therapy that can ameliorate heat stroke victims by attenuating activated coagulation, systemic inflammation, and vital organ ischemia/injury during heat stroke.

'Chronomics' in ICU: circadian aspects of immune response and therapeutic perspectives in the critically ill

Complex interrelations exist between the master central clock, located in the suprachiasmatic nuclei of the hypothalamus, and several peripheral clocks, such as those found in different immune cells of the body. Moreover, external factors that are called ‘timekeepers’, such as light/dark and sleep/wake cycles, interact with internal clocks by synchronizing their different oscillation phases. Chronobiology is the science that studies biologic rhythms exhibiting recurrent cyclic behavior. Circadian rhythms have a duration of approximately 24 h and can be assessed through chronobiologic analysis of time series of melatonin, cortisol, and temperature. Critically ill patients experience severe circadian deregulation due to not only the lack of effective timekeepers in the intensive care unit (ICU) environment but also systemic inflammation. The latter has been found in both animal and human studies to disrupt circadian rhythmicity of all measured biomarkers. The aims of this article are to describe circadian physiology during acute stress and to discuss the effects of ICU milieu upon circadian rhythms, in order to emphasize the value of considering circadian-immune disturbance as a potential tool for personalized treatment. Thus, besides neoplastic processes, critical illness could be linked to what has been referred as ‘chronomics’: timing and rhythm. In addition, different therapeutic perspectives will be presented in association with environmental approaches that could restore circadian connection and hasten physical recovery.

Melatonin improves outcomes of heatstroke in mice by reducing brain inflammation and oxidative damage and multiple organ dysfunction

We report here that when untreated mice underwent heat stress, they displayed thermoregulatory deficit (e.g., animals display hypothermia during room temperature exposure), brain (or hypothalamic) inflammation, ischemia, oxidative damage, hypothalamic-pituitary-adrenal axis impairment (e.g., decreased plasma levels of both adrenocorticotrophic hormone and corticosterone during heat stress), multiple organ dysfunction or failure, and lethality. Melatonin therapy significantly reduced the thermoregulatory deficit, brain inflammation, ischemia, oxidative damage, hypothalamic-pituitary-adrenal axis impairment, multiple organ dysfunction, and lethality caused by heat stroke. Our data indicate that melatonin may improve outcomes of heat stroke by reducing brain inflammation, oxidative damage, and multiple organ dysfunction.

Ischemic and oxidative damage to the hypothalamus may be responsible for heat stroke

The hypothalamus may be involved in regulating homeostasis, motivation, and emotional behavior by controlling autonomic and endocrine activity. The hypothalamus communicates input from the thalamus to the pituitary gland, reticular activating substance, limbic system, and neocortex. This allows the output of pituitary hormones to respond to changes in autonomic nervous system activity. Environmental heat stress increases cutaneous blood flow and metabolism, and progressively decreases splanchnic blood flow. Severe heat exposure also decreases mean arterial pressure (MAP), increases intracranial pressure (ICP), and decreases cerebral perfusion pressure (CPP = MAP - ICP), all of which lead to cerebral ischemia and hypoxia. Compared with normothermic controls, rodents with heatstroke have higher hypothalamic values of cellular ischemia (e.g., glutamate and lactate-to-pyruvate ratio) and damage (e.g., glycerol) markers, pro-oxidant enzymes (e.g., lipid peroxidation and glutathione oxidation), proinflammatory cytokines (e.g., interleukin-1β and tumor necrosis factor-α), inducible nitric oxide synthase-dependent nitric oxide, and an indicator for the accumulation of polymorphonuclear leukocytes (e.g., myeloperoxidase activity), as well as neuronal damage (e.g., apoptosis, necrosis, and autophagy) after heatstroke. Hypothalamic values of antioxidant defenses (e.g., glutathione peroxidase and glutathione reductase), however, are lower. The ischemic, hypoxic, and oxidative damage to the hypothalamus during heatstroke may cause multiple organ dysfunction or failure through hypothalamic-pituitary-adrenal axis mechanisms. Finding the link between the signaling and heatstroke-induced hypothalamic oxidative and ischemic damage might allow us to clinically attenuate heatstroke. In particular, free radical scavengers, heat shock protein-70 inducers, hypervolemic hemodilution, inducible nitric oxide synthase inhibitors, progenitor stem cells, flutamide, estrogen, interleukin-1 receptor antagonists, glucocorticoid, activated protein C, and baicalin mitigate preclinical heatstroke levels.

Melatonin: buffering the immune system

Melatonin modulates a wide range of physiological functions with pleiotropic effects on the immune system. Despite the large number of reports implicating melatonin as an immunomodulatory compound, it still remains unclear how melatonin regulates immunity. While some authors argue that melatonin is an immunostimulant, many studies have also described anti-inflammatory properties. The data reviewed in this paper support the idea of melatonin as an immune buffer, acting as a stimulant under basal or immunosuppressive conditions or as an anti-inflammatory compound in the presence of exacerbated immune responses, such as acute inflammation. The clinical relevance of the multiple functions of melatonin under different immune conditions, such as infection, autoimmunity, vaccination and immunosenescence, is also reviewed.

A review of the molecular aspects of melatonin's anti-inflammatory actions: recent insights and new perspectives

Melatonin is a highly evolutionary conserved endogenous molecule that is mainly produced by the pineal gland, but also by other nonendocrine organs, of most mammals including man. In the recent years, a variety of anti-inflammatory and antioxidant effects have been observed when melatonin is applied exogenously under both in vivo and in vitro conditions. A number of studies suggest that this indole may exert its anti-inflammatory effects through the regulation of different molecular pathways. It has been documented that melatonin inhibits the expression of the isoforms of inducible nitric oxide synthase and cyclooxygenase and limits the production of excessive amounts of nitric oxide, prostanoids, and leukotrienes, as well as other mediators of the inflammatory process such as cytokines, chemokines, and adhesion molecules. Melatonin's anti-inflammatory effects are related to the modulation of a number of transcription factors such as nuclear factor kappa B, hypoxia-inducible factor, nuclear factor erythroid 2-related factor 2, and others. Melatonin's effects on the DNA-binding capacity of transcription factors may be regulated through the inhibition of protein kinases involved in signal transduction, such as mitogen-activated protein kinases. This review summarizes recent research data focusing on the modulation of the expression of different inflammatory mediators by melatonin and the effects on cell signaling pathways responsible for the indole's anti-inflammatory activity. Although there are a numerous published reports that have analyzed melatonin's anti-inflammatory properties, further studies are necessary to elucidate its complex regulatory mechanisms in different cellular types and tissues.

Hypobaric hypoxia preconditioning attenuates experimental heatstroke syndromes via preinduction of heat shock protein 70

INTRODUCTION

Heatstroke has been defined as a form of hyperthermia associated with a systemic inflammatory response that leads to multiple organ dysfunction syndrome (MODS). It has also been documented that heat shock protein 70 (HSP70) preconditioning is able to induce thermotolerance. Here, the authors further investigated whether hypobaric hypoxia preconditioning (HHP) improved the MODS in heatstroke by up-regulation of HSP70.

METHODS

Anesthetized rats were randomly assigned to (a) non-HHP + nonheated group, (b) non-HHP + heated group, (c) HHP + heated group and (d) HHP + HSP70 antibodies (Abs) + heated groups. All heated groups were exposed to heat stress (43°C, 70 minutes) to induce heatstroke. For HHP, animals were exposed to 0.66 atmosphere absolute (18.3% O2) for 5 hours daily for consecutive 5 days per week for 2 weeks before the start of heat exposure.

RESULTS

HHP significantly (i) attenuated hypotension, (ii) reduced plasma index of the toxic oxidizing radicals and the organ injury indicator, (iii) attenuated plasma systemic inflammatory response molecules, (iv) reduced an index of infiltration of polymorphonuclear neutrophils in the lung like myeloper-oxidase activity, (v) promoted plasma levels of an anti-inflammatory cytokine, interleukin-10, (vi) promoted the survival time to fourfold compared with non-HHP group and (vii) promoted the overexpression of HSP70 in different organs (eg, the lung) during heatstroke. The beneficial effects of HHP could be significantly attenuated by HSP70 Ab preconditioning.

CONCLUSION

Our results show that HHP protects rats from heat-induced MODS via up-regulating HSP70. Thus, HHP could be a novel strategy for the prevention of heatstroke animals or patients before heat exposure.

Melatonin prevents hemorrhagic shock-induced liver injury in rats through an Akt-dependent HO-1 pathway

Although melatonin treatment following trauma-hemorrhage or ischemic reperfusion prevents organs from dysfunction and injury, the precise mechanism remains unknown. This study tested whether melatonin prevents liver injury following trauma-hemorrhage involved the protein kinase B (Akt)-dependent heme oxygenase (HO)-1 pathway. After a 5-cm midline laparotomy, male rats underwent hemorrhagic shock (mean blood pressure approximately 40 mmHg for 90 min) followed by fluid resuscitation. At the onset of resuscitation, rats were treated with vehicle, melatonin (2 mg/kg), or melatonin plus phosphoinositide 3-kinase (PI3K) inhibitor wortmannin (1 mg/kg). At 2 hr after trauma-hemorrhage, the liver tissue myeloperoxidase activity, malondialdehyde, adenosine triphosphate, serum alanine aminotransferase, and aspartate aminotransferase levels were significantly increased compared with sham-operated control. Trauma-hemorrhage resulted in a significant decrease in the Akt activation in comparison with the shams (relative density, 0.526 ± 0.031 versus 1.012 ± 0.066). Administration of melatonin following trauma-hemorrhage normalized liver Akt phosphorylation (0.993 ± 0.061), further increased mammalian target of rapamycin (mTOR) activation (5.263 ± 0.338 versus 2.556 ± 0.225) and HO-1 expression (5.285 ± 0.325 versus 2.546 ± 0.262), and reduced cleaved caspase-3 levels (2.155 ± 0.297 versus 5.166 ± 0.309). Coadministration of wortmannin abolished the melatonin-mediated attenuation of the shock-induced liver injury markers. Our results collectively suggest that melatonin prevents hemorrhagic shock-induced liver injury in rats through an Akt-dependent HO-1 pathway.

Melatonin modulates TLR4-mediated inflammatory genes through MyD88- and TRIF-dependent signaling pathways in lipopolysaccharide-stimulated RAW264.7 cells

Increasing evidence demonstrates that melatonin has an anti-inflammatory effect. Nevertheless, the molecular mechanisms remain obscure. In this study, we investigated the effect of melatonin on toll-like receptor 4 (TLR4)-mediated molecule myeloid differentiation factor 88 (MyD88)-dependent and TRIF-dependent signaling pathways in lipopolysaccharide (LPS)-stimulated macrophages. RAW264.7 cells were incubated with LPS (2.0 μg/mL) in the absence or presence of melatonin (10, 100, 1000 μm). As expected, melatonin inhibited TLR4-mediated tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6, IL-8, and IL-10 in LPS-stimulated macrophages. In addition, melatonin significantly attenuated LPS-induced upregulation of cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) in macrophages. Further analysis showed that melatonin inhibited the expression of MyD88 in LPS-stimulated macrophages. Although it had no effect on TLR4-mediated phosphorylation of c-Jun N-terminal kinase (JNK), p38, and extracellular regulated protein kinase (ERK), melatonin significantly attenuated the activation of nuclear factor kappa B (NF-κB) in LPS-stimulated macrophages. In addition, melatonin inhibited TLR4-mediated Akt phosphorylation in LPS-stimulated macrophages. Moreover, melatonin significantly attenuated the elevation of interferon (IFN)-regulated factor-3 (IRF3), which was involved in TLR4-mediated TRIF-dependent signaling pathway, in LPS-stimulated macrophages. Correspondingly, melatonin significantly alleviated LPS-induced IFN-β in macrophages. In conclusion, melatonin modulates TLR4-mediated inflammatory genes through MyD88-dependent and TRIF-dependent signaling pathways.

Melatonin reduces acute lung inflammation, edema, and hemorrhage in heatstroke rats

AIM

To assess the therapeutic effect of melatonin on heat-induced acute lung inflammation and injury in rats.

METHODS

Heatstroke was induced by exposing anesthetized rats to heat stress (36 °C, 100 min). Rats were treated with vehicle or melatonin (0.2, 1, 5 mg/kg) by intravenous administration 100 min after the initiatioin of heatstroke and were allowed to recover at room temperature (26 °C). The acute lung injury was quantified by morphological examination and by determination of the volume of pleural exudates, the number of polymorphonuclear (PMN) cells, and the myeloperoxidase (MPO) activity. The concentrations of tumor necrosis factor, interleukin (IL)-1β, IL-6, and IL-10 in bronchoalveolar fluid (BALF) were measured by ELISA. Nitric oxide (NO) level was determined by Griess method. The levels of glutamate and lactate-to-pyruvate ratio were analyzed by CMA600 microdialysis analyzer. The concentrations of hydroxyl radicals were measured by a procedure based on the hydroxylation of sodium salicylates leading to the production of 2,3-dihydroxybenzoic acid (DHBA).

RESULTS

Melatonin (1 and 5 mg/kg) significantly (i) prolonged the survival time of heartstroke rats (117 and 186 min vs 59 min); (ii) attenuated heatstroke-induced hyperthermia and hypotension; (iii) attenuated acute lung injury, including edema, neutrophil infiltration, and hemorrhage scores; (iv) down-regulated exudate volume, BALF PMN cell number, and MPO activity; (v) decreased the BALF levels of lung inflammation response cytokines like TNF-alpha, interleukin (IL)-1β, and IL-6 but further increased the level of an anti-inflammatory cytokine IL-10; (vi) reduced BALF levels of glutamate, lactate-to-pyruvate ratio, NO, 2,3-DHBA, and lactate dehydrogenase.

CONCLUSION

Melatonin may improve the outcome of heatstroke in rats by attenuating acute lung inflammation and injury.

Flutamide, an androgen receptor antagonist, improves heatstroke outcomes in mice

Flutamide has been used as an adjunct for decreasing the mortality from subsequent sepsis. Heatstroke resembles septic shock in many aspects. We hypothesized that heat-induced multiple organ dysfunction syndromes and lethality could be reduced by flutamide therapy. In heatstroke groups, mice were exposed to whole body heating (41.2°C, for 1h) in a controlled-environment chamber. The heat-stressed mice were returned to normal room temperature (24°C) after whole body heating. Mice still alive on day 4 of WBH treatment were considered survivors. Physiological and biochemical parameters were monitored for 2.5h post-WBH. Heatstroke mice were subcutaneously treated with flutamide (12.5-50mg/kg body weight in 0.05 ml) or vehicle solution (0.05 ml/kg body weight) once daily for 3 consecutive days post-WBH. We evaluated the effect of flutamide in heatstroke mice and showed that flutamide significantly (i) attenuated hypothermia, (ii) reduced the number of apoptotic cells in the hypothalamus, the spleen, the liver, and the kidney, (iii) attenuated the plasma index of toxic oxidizing radicals (e.g., nitric oxide metabolites and hydroxyl radicals), (iv) diminished the plasma index of the organ injury index (e.g., lactate dehydrogenase), (v) attenuated plasma systemic inflammation response molecules (e.g., tumor necrosis factor-α and interleukin-6), (vi) reduced the index of infiltration of polymorphonuclear neutrophils in the lung (e.g., myeloperoxidase activity), and (vii) allowed three times the fractional survival compared with vehicle. Thus, flutamide appears to be a novel agent for the treatment of mice with heatstroke or patients in the early stage of heatstroke.

Beneficial effects of melatonin on stroke-induced muscle atrophy in focal cerebral ischemic rats

MUSCLE ATROPHY IS THE RESULT OF TWO OPPOSING CONDITIONS THAT CAN BE FOUND IN PATHOLOGICAL OR DISEASED MUSCLES: an imbalance in protein synthesis and degradation mechanisms. Thus, we investigated whether exogenous melatonin could regulate muscle components in stroke-induced muscle atrophy in rats. Comparing muscle phenotypes, we found that long-term melatonin administration could influence muscle mass. Muscle atrophy-related genes, including muscle atrophy F-box (MAFbx) and muscle ring finger 1 (MuRF1) were significantly down-regulated in melatonin-administered rats in the gastrocnemius. However, only MAFbx at the mRNA level was attenuated in the soleus of melatonin-administered rats. Insulin-like growth factor-1 receptor (IGF-1R) was significantly over-expressed in melatonin-administered rats in both the gastrocnemius and soleus muscles. Comparing myosin heavy chain (MHC) components, in the gastrocnemius, expression of both slow- and fast-type isoforms were significantly enhanced in melatonin-administered rats. These results suggest that long-term exogenous melatonin-administration may have a prophylactic effect on muscle atrophy through the MuRF1/MAFbx signaling pathway, as well as a potential therapeutic effect on muscle atrophy through the IGF-1-mediated hypertrophic signaling pathway in a stroke animal model.