We previously reported that heat stroke induces autophagy as a protection mechanism against neurodegeneration in the brain. Heme oxygenase (HO)-1 is a stress protein and can be induced by heat stress (HS). Cerebellar Purkinje cells are selectively vulnerable to heat-induced injury. In this study, we first validated an animal model of HS (38°C for 4 h) in which sustained increase of Purkinje cell injury, HO-1 expression up to 24 h post HS (HS₂₄), and hyperthermia reaching a rectal temperature 41.52 ± 0.32 were observed. In subsequent experiments, we investigated the effects of HO-1 on HS-induced Purkinje cell injury. Rats were divided into four groups: one normothermic control group receiving saline vehicle (1 mL/kg, intraperitoneal [i.p.]) and exposed to 25 for 4 h; and three HS groups receiving saline, or HO-1 inducer haemin (30 mg/kg, i.p.) or HO-1 inhibitor tin protoporphyrin (SnPP, 30 mg/kg, i.p.), respectively, at 12 h prior to HS. HS-induced Purkinje cell injury was further enhanced by HO-1 inducer but attenuated by HO-1 inhibitor as evaluated by immunoreactivity of apoptosis marker (active caspase-3) as well as Fluoro-Jade B histochemistry (staining for degenerating neurons), suggesting a detrimental role of HO-1. Interestingly, the protective autophagy was reduced by HO-1 inducer but enhanced by HO-1 inhibitor as demonstrated by autophagy markers including Beclin-1 and microtubule-associated protein light chain 3 in Purkinje cells. Double immunofluorescent labelling of Beclin-1 or 8-hydroxydeoxyguanosine (an oxidative DNA damage marker) with HO-1 immunoreactivity not only demonstrated their co-localization, but also confirmed that HO-1 negatively regulated Beclin-1 but increased oxidative stress in the same Purkinje cell. Taken together, our results indicate that HO-1 aggravates HS injury in cerebellar Purkinje cells. Our findings shed new light on cell damage mechanisms by HS in central nervous system and may help to provide potential therapeutic foci.

Heat stroke (HS) is defined clinically as a condition when core body temperature rises above 40°C and is accompanied by central nervous system abnormalities. In this study, we established a rat model of HS by exposing anesthetized rats to elevated ambient temperature (40°C) until core temperature reaching 40.5°C (HS onset). The rat was immediately removed from heating chamber, allowed recovery for various time periods, and killed for histological and biochemical studies. Our results indicated neuronal shrinkage and pyknosis of the nucleus and sustained up to 12 h recovery time in cerebral cortex. Elevated expression of autophagy-related proteins, including microtubule associated protein light chain 3 and beclin 1 in cortical tissue at various times (3, 6, 12 h) of recovery was observed. In addition, the number of autophagosomes stained by monodansylcadaverine, a specific autophagosome marker, increased after heat exposure but was reduced by pretreatment with 3-methyladenine, an autophagy inhibitor. Furthermore, heat exposure increased neuronal degeneration in cortical tissue, as evidenced by staining with the fluorescent dye Fluoro-Jade B for degenerating neuron. Pretreatment with 3-methyladenine in HS rats aggravated neurodegeneration. Taken together, these results suggest that HS induces autophagy as a protection mechanism against neurodegeneration. Modulation of autophagy may provide a potential therapeutic approach for HS and await further research.

Objective Recent advances in perirenal adipose tissue (PAT) highlighted that PAT might involve in the pathogenesis of chronic inflammatory and dysfunctional metabolic diseases. This study assessed the association between perirenal fat thickness (PrFT) and metabolic dysfunction-associated fatty liver disease (MALFD) in type 2 diabetes mellitus (T2DM). Methods This study comprised 867 eligible participants with T2DM. Trained reviewers collected anthropometric and biochemical measurements. The diagnosis of MAFLD was based on the latest international expert consensus statement. PrFT and fatty liver were evaluated by computed tomography. The visceral fat area (VFA) and subcutaneous fat area (SFA) were measured by bioelectrical impedance analysis. The non-alcoholic fatty liver disease fibrosis score (NFS) and fibrosis-4 (FIB-4) index were used to assess progressive liver fibrosis in MAFLD. Results Overall, the prevalence of MAFLD was 62.3% in T2DM. The PrFT in the MAFLD group was statistically increased than in the non-MAFLD group ( P < 0.05). Correlation analysis showed that PrFT was significantly correlated with dysfunctional metabolic factors like body mass index, waist circumference, triglycerides, high-density lipoprotein cholesterol, systolic blood pressure, diastolic blood pressure, uric acid, and insulin resistance. Multiple regression analysis revealed that PrFT was positively correlated with NFS ( β =0.146, P <0.001) and FIB-4 ( β =0.082, P =0.025) in the MAFLD. In contrast, PrFT was negatively correlated with CT L-S ( β =−0.188, P <0.001). Furthermore, PrFT was also significantly associated with MAFLD independent of VFA and SFA, the OR (95% CI) was 1.279 (1.191–1.374). Meanwhile, PrFT also had a good identifying value for MAFLD as VFA. The area under the curve (95% CI) value of PrFT identifying MAFLD was 0.782 (0.751–0.812). The optimal cut-off value of PrFT was 12.6mm, with a sensitivity of 77.8% and specificity of 70.8%. Conclusion PrFT was independently associated with MAFLD, NFS, and FIB-4 and showed a similar identifying value for MAFLD as VFA, which suggested that PrFT can be used as an alternative index to VFA.