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Amino acid solution mitigates hypothermia response and intestinal damage following exertional heat stroke in male mice.

ABSTRACT: Increased gut permeability is implicated in the initiation and extent of the cytokine inflammatory response associated with exertional heat stroke (EHS). The primary objective of this study was to determine if a five amino acid oral rehydration solution (5AAS), specifically designed for the protection of the gastrointestinal lining, would prolong time to EHS, maintain gut function and dampen the systemic inflammatory response (SIR) measured during EHS recovery. Male C57/BL6J mice instrumented with radiotelemetry were gavaged with 150 μL of 5AAS or H₂ O, and ≈12 h later were either exposed to an EHS protocol where mice exercised in a 37.5°C environmental chamber to a self-limiting maximum core temperature (Tc,max) or performed the exercise control (EXC) protocol (25°C). 5AAS pretreatment attenuated hypothermia depth and length (p < 0.005), which are indicators of EHS severity during recovery, without any effect on physical performance or thermoregulatory responses in the heat as determined by percent body weight lost (≈9%), max speed (≈6 m/min), distance (≈700 m), time to Tc,max (≈160 min), thermal area (≈550°C∙min), and Tc,max (42.2°C). EHS groups treated with 5AAS showed a significant decrease in gut transepithelial conductance, decreased paracellular permeability, increased villus height, increased electrolyte absorption and changes in tight junction protein expression pattern suggestive of improved barrier integrity (p < 0.05). No differences were witnessed between EHS groups in acute phase response markers of liver, circulating SIR markers, or indicators of organ damage during recovery. These results suggest that a 5AAS improves Tc regulation during EHS recovery through maintaining mucosal function and integrity.

SUBMITTER: King MA

PROVIDER: S-EPMC10202825 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature

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Amino acid solution mitigates hypothermia response and intestinal damage following exertional heat stroke in male mice.

King Michelle A MA Grosche Astrid A Ward Shauna M SM Ward Jermaine A JA Sasidharan Anusree A Mayer Thomas A TA Plamper Mark L ML Xu Xiaodong X Ward Matthew D MD Clanton Thomas L TL Vidyasagar Sadasivan S

Physiological reports 20230501 10

Increased gut permeability is implicated in the initiation and extent of the cytokine inflammatory response associated with exertional heat stroke (EHS). The primary objective of this study was to determine if a five amino acid oral rehydration solution (5AAS), specifically designed for the protection of the gastrointestinal lining, would prolong time to EHS, maintain gut function and dampen the systemic inflammatory response (SIR) measured during EHS recovery. Male C57/BL6J mice instrumented wi ...[more]

PMID: 37217446

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Project description:BackgroundRhabdomyolysis (RM) is a common complication of exertional heat stroke (EHS) and constitutes a direct cause of death. However, the mechanism underlying RM following EHS remains unclear.MethodsThe murine EHS model was prepared by our previous protocol. RNA sequencing is applied to identify the pathological pathways that contribute to RM following EHS. Inhibition of the acyl-CoA synthetase long-chain family member 4 (ACSL4) was achieved by RNA silencing in vitro prior to ionomycin plus heat stress exposure or pharmacological inhibitors in vivo prior to heat and exertion exposure. The histological changes, the iron accumulation, oxidized phosphatidylethanolamines species, as well as histological evaluation and levels of lipid metabolites in skeletal muscle tissues were measured.ResultsWe demonstrated that ferroptosis contributes to RM development following EHS. Ferroptosis inhibitor ferrostatin-1 administration once EHS onset significantly ameliorated the survival rate of EHS mice from 35.357% to 52.288% within 24 h after EHS (P = 0.0028 compared with control) and markedly inhibited RM development induced by EHS. By comparing gene expression of between sham heat rest (SHR) (n = 3) and EHS (n = 3) mice in the gastrocnemius (Gas) muscle tissue, we identified that Acsl4 mRNA expression is elevated in Gas muscle tissue of EHS mice (P = 0.0038 compared with SHR), so as to its protein levels (P = 0.0001 compared with SHR). Followed by increase in creatine kinase (CK) and myoglobin (MB) levels, the labile iron accumulation, decrease in glutathione peroxidase 4 (GPX4) expression, and elevation of lipid peroxidation products. From in vivo and in vitro experiments, inhibition of Acsl4 significantly improves muscle cell death caused by EHS, thereby ameliorating RM development, followed by reduction in CK and MB levels by 30-40% (P < 0.0001; n = 8-10) and 40% (P < 0.0001; n = 8-10), restoration of GPX4 expression, and decrease in lipid peroxidation products. Mechanistically, ACSL4-mediated RM seems to be Yes-associated protein (YAP) dependent via TEA domain transcription factor1/TEA domain transcription factor4.ConclusionsThese findings demonstrate an important role of ACSL4 in mediating ferroptosis activation in the development of RM following EHS and suggest that targeting ACSL4 may represent a novel therapeutic strategy to limit the skeletal muscle cell death and prevent RM after EHS.

Project description:Rationale: Record-breaking heatwaves caused by greenhouse effects lead to multiple hyperthermia disorders, the most serious of which is exertional heat stroke (EHS) with the mortality reaching 60 %. Repeat exercise with heat exposure, termed heat acclimation (HA), protects against EHS by fine-tuning feedback control of body temperature (Tb), the mechanism of which is opaque. This study aimed to explore the molecular and neural circuit mechanisms of the HA training against EHS. Methods: Male C57BL/6 mice (6-8 weeks) and male TRPV1-Cre mice (6-8 weeks) were used in our experiments. The EHS model with or without HA training were established for this study. RNA sequencing, qPCR, immunoblot, immunofluorescent assays, calcium imaging, optogenetic/ chemical genetic intervention, virus tracing, patch clamp, and other methods were employed to investigate the molecular mechanism and neural circuit by which HA training improves the function of the medial preoptic area (mPOA) neurons. Furthermore, a novel exosome-based strategy targeting the central nervous system to deliver irisin, a protective peptide generated by HA, was established to protect against EHS. Results: HA-related neurons in the mPOA expressing transient receptor potential vanilloid-1 (TRPV1) were identified as a population whose activation reduces Tb; inversely, dysfunction of these neurons contributes to hyperthermia and EHS. mPOATRPV1 neurons facilitate vasodilation and reduce adipose tissue thermogenesis, which is associated with their inhibitory projection to the raphe pallidus nucleus (RPa) and dorsal medial hypothalamus (DMH) neurons, respectively. Furthermore, HA improves the function of preoptic heat-sensitive neurons by enhancing TRPV1 expression, and Trpv1 ablation reverses the HA-induced heat tolerance. A central nervous system-targeted exosome strategy to deliver irisin, a protective peptide generated by HA, can promote preoptic TRPV1 expression and exert similar protective effects against EHS. Conclusions: Preoptic TRPV1 neurons could be enhanced by HA, actively contributing to heat defense through the mPOA"DMH/RPa circuit during EHS, which results in the suppression of adipose tissue thermogenesis and facilitation of vasodilatation. A delivery strategy of exosomes engineered with RVG-Lamp2b-Irisin significantly improves the function of mPOATRPV1 neurons, providing a promising preventive strategy for EHS in the future.

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Amino acid solution mitigates hypothermia response and intestinal damage following exertional heat stroke in male mice.

Publications

Amino acid solution mitigates hypothermia response and intestinal damage following exertional heat stroke in male mice.

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