Xuebijing Injection Attenuates Heat Stroke-Induced Brain Injury through Oxidative Stress Blockage and Parthanatos Modulation via PARP-1/AIF Signaling

The significant mechanism and treatments of cell death in heatstroke

With global warming, extreme environmental heat is becoming a social issue of concern, which can cause adverse health results including heatstroke (HS). Severe heat stress is characterized by cell death of direct heat damage, excessive inflammatory responses, and coagulation disorders that can lead to multiple organ dysfunction (MODS) and even death. However, the significant pathophysiological mechanism and treatment of HS are still not fully clear. Various modes of cell death, including apoptosis, pyroptosis, ferroptosis, necroptosis and PANoptosis are involved in MODS induced by heatstroke. In this review, we summarized molecular mechanism, key transcriptional regulation as for HSF1, NRF2, NF-κB and PARP-1, and potential therapies of cell death resulting in CNS, liver, intestine, reproductive system and kidney injury induced by heat stress. Understanding the mechanism of cell death provides new targets to protect multi-organ function in HS.

Hyperbaric oxygen therapy attenuates heatstroke-induced hippocampal injury by inhibiting microglial pyroptosis

Background: Central nervous system (CNS) injury is the most prominent feature of heatstroke and the hippocampus is prone to damage. However, the mechanisms underlying the heatstroke-induced hippocampal injury remain unclear. Hyperbaric oxygen (HBO) therapy prevents CNS injury in heatstroke mice. However, the underlying mechanisms of HBO in heatstroke-induced hippocampal injury remain unclear. This study aimed to elucidate the protective effects of HBO against hippocampal injury and its potential role in microglial pyroptosis in heatstroke rats.Methods: A rat heatstroke model and a heat stress model with a mouse microglial cell line (BV2) were, respectively, used to illustrate the effect of HBO on heat-induced microglial pyroptosis in vivo and in vitro. We used a combination of molecular and histological methods to assess microglial pyroptosis and neuroinflammation both in vivo and in vitro.Results: The results revealed that HBO improved heatstroke-induced survival outcomes, hippocampal injury, and neurological dysfunction in rats. In addition, HBO mitigates microglial pyroptosis and reduces the expression of pro-inflammatory cytokines in the hippocampus of heatstroke rats. In vitro experiments showed that HBO attenuated BV2 cell injury under heat stress. Furthermore, HBO prevented heat-induced pyroptosis of BV2 cells, and the expression of pro-inflammatory cytokines IL-18 and IL-1β was reduced. Mechanistically, HBO alleviates heatstroke-induced neuroinflammation and hippocampal injury by preventing microglial pyroptosis. Conclusions: In conclusion, HBO attenuates heatstroke-induced neuroinflammation and hippocampal injury by inhibiting microglial pyroptosis.

INFLUENCES OF HEAT STRESS ON GLUTAMATE TRANSMISSION-DEPENDENT EXPRESSION LEVELS OF IL-1β and IL-18 IN BV-2 MICROGLIAL CELLS

ABSTRACT

Objective: This study aimed to explore the impact of heat stress (HS) on glutamate transmission-dependent expression levels of interleukin-1β (IL-1β) and IL-18 in BV-2 microglial cells. Methods: BV-2 microglial cells were cultured in vitro , with cells maintained at 37°C serving as the control. The HS group experienced incubation at 40°C for 1 h, followed by further culturing at 37°C for 6 or 12 h. The experimental group was preincubated with glutamate, the glutamate antagonist riluzole, or the mGluR5 agonist, 2-chloro-5-hydroxyphenylglycine (CHPG), before HS. Glutamate content in BV-2 culture supernatant was assessed using colorimetric assay. Moreover, mRNA expression levels of EAAT3 and/or mGluR5 in BV-2 cells were determined via quantitative polymerase chain reaction. Interleukins (IL-1β and IL-18) in cell culture supernatant were measured using enzyme-linked immunosorbent assay. Western blot analysis was employed to assess protein levels of IL-1β and IL-18 in BV-2 cells. Results: HS induced a significant release of glutamate and increased the expression levels of mGluR5 and EAAT3 in BV-2 cells. It also triggered the expression levels and release of proinflammatory factors, such as IL-1β and IL-18, synergizing with the effects of glutamate treatment. Preincubation with both riluzole and CHPG significantly reduced HS-induced glutamate release and mitigated the increased expression levels and release of IL-1β and IL-18 induced by HS. Conclusion: The findings confirmed that microglia could be involved in HS primarily through glutamate metabolisms, influencing the expression levels and release of IL-1β and IL-18.

Early Pulmonary Fibrosis-like Changes in the Setting of Heat Exposure: DNA Damage and Cell Senescence

It is well known that extreme heat events happen frequently due to climate change. However, studies examining the direct health impacts of increased temperature and heat waves are lacking. Previous reports revealed that heatstroke induced acute lung injury and pulmonary dysfunction. This study aimed to investigate whether heat exposure induced lung fibrosis and to explore the underlying mechanisms. Male C57BL/6 mice were exposed to an ambient temperature of 39.5 ± 0.5 °C until their core temperature reached the maximum or heat exhaustion state. Lung fibrosis was observed in the lungs of heat-exposed mice, with extensive collagen deposition and the elevated expression of fibrosis molecules, including transforming growth factor-β1 (TGF-β1) and Fibronectin (Fn1) (p < 0.05). Moreover, epithelial-mesenchymal transition (EMT) occurred in response to heat exposure, evidenced by E-cadherin, an epithelial marker, which was downregulated, whereas markers of EMT, such as connective tissue growth factor (CTGF) and the zinc finger transcriptional repressor protein Slug, were upregulated in the heat-exposed lung tissues of mice (p < 0.05). Subsequently, cell senescence examination revealed that the levels of both senescence-associated β-galactosidase (SA-β-gal) staining and the cell cycle protein kinase inhibitor p21 were significantly elevated (p < 0.05). Mechanistically, the cGAS-STING signaling pathway evoked by DNA damage was activated in response to heat exposure (p < 0.05). In summary, we reported a new finding that heat exposure contributed to the development of early pulmonary fibrosis-like changes through the DNA damage-activated cGAS-STING pathway followed by cellular senescence.