College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, China.
CNS Neurosci Ther. 2024 Jul;30(7):e14840. doi: 10.1111/cns.14840.
Heat stress (HS) commonly occurs as a severe pathological response when the body's sensible temperature exceeds its thermoregulatory capacity, leading to the development of chronic brain inflammation, known as neuroinflammation. Emerging evidence suggests that HS leads to the disruption of the gut microbiota, whereas abnormalities in the gut microbiota have been demonstrated to affect neuroinflammation. However, the mechanisms underlying the effects of HS on neuroinflammation are poorly studied. Meanwhile, effective interventions have been unclear. β-Hydroxybutyric acid (BHBA) has been found to have neuroprotective and anti-inflammatory properties in previous studies. This study aims to explore the modulatory effects of BHBA on neuroinflammation induced by HS and elucidate the underlying molecular mechanisms.
An in vivo and in vitro model of HS was constructed under the precondition of BHBA pretreatment. The modulatory effects of BHBA on HS-induced neuroinflammation were explored and the underlying molecular mechanisms were elucidated by flow cytometry, WB, qPCR, immunofluorescence staining, DCFH-DA fluorescent probe assay, and 16S rRNA gene sequencing of colonic contents.
Heat stress was found to cause gut microbiota disruption in HS mouse models, and TM7 and [Previotella] spp. may be the best potential biomarkers for assessing the occurrence of HS. Fecal microbiota transplantation associated with BHBA effectively reversed the disruption of gut microbiota in HS mice. Moreover, BHBA may inhibit microglia hyperactivation, suppress neuroinflammation (TNF-α, IL-1β, and IL-6), and reduce the expression of cortical endoplasmic reticulum stress (ERS) markers (GRP78 and CHOP) mainly through its modulatory effects on the gut microbiota (TM7, Lactobacillus spp., Ruminalococcus spp., and Prevotella spp.). In vitro experiments revealed that BHBA (1 mM) raised the expression of the ERS marker GRP78, enhanced cellular activity, and increased the generation of reactive oxygen species (ROS) and anti-inflammatory cytokines (IL-10), while also inhibiting HS-induced apoptosis, ROS production, and excessive release of inflammatory cytokines (TNF-α and IL-1β) in mouse BV2 cells.
β-Hydroxybutyric acid may be an effective agent for preventing neuroinflammation in HS mice, possibly due to its ability to inhibit ERS and subsequent microglia neuroinflammation via the gut-brain axis. These findings lay the groundwork for future research and development of BHBA as a preventive drug for HS and provide fresh insights into techniques for treating neurological illnesses by modifying the gut microbiota.
当人体的感知温度超过其体温调节能力时，热应激（HS）通常会作为一种严重的病理反应发生，导致慢性脑炎症，即神经炎症的发展。新出现的证据表明，HS 会导致肠道微生物群的破坏，而肠道微生物群的异常已被证明会影响神经炎症。然而，HS 对神经炎症影响的机制仍研究甚少。同时，有效的干预措施尚不清楚。β-羟基丁酸（BHBA）在先前的研究中已被发现具有神经保护和抗炎特性。本研究旨在探讨 BHBA 对 HS 诱导的神经炎症的调节作用，并阐明潜在的分子机制。
在 BHBA 预处理的前提下，构建 HS 的体内和体外模型。通过流式细胞术、WB、qPCR、免疫荧光染色、DCFH-DA 荧光探针检测和结肠内容物 16S rRNA 基因测序，探讨 BHBA 对 HS 诱导的神经炎症的调节作用及其潜在的分子机制。
热应激导致 HS 小鼠模型肠道微生物群发生破坏，TM7 和 [Prevotella] spp.可能是评估 HS 发生的最佳潜在生物标志物。与 BHBA 相关的粪便微生物群移植可有效逆转 HS 小鼠肠道微生物群的破坏。此外，BHBA 可能通过调节肠道微生物群（TM7、乳杆菌属、瘤胃球菌属和普雷沃氏菌属）抑制小胶质细胞过度激活，抑制神经炎症（TNF-α、IL-1β 和 IL-6），降低皮质内质网应激（ERS）标志物（GRP78 和 CHOP）的表达。体外实验表明，BHBA（1 mM）提高了 ERS 标志物 GRP78 的表达，增强了细胞活性，增加了活性氧（ROS）和抗炎细胞因子（IL-10）的产生，同时抑制了 HS 诱导的小鼠 BV2 细胞凋亡、ROS 产生和炎症细胞因子（TNF-α和 IL-1β）的过度释放。
β-羟基丁酸可能是预防 HS 小鼠神经炎症的有效药物，这可能是由于其通过肠道-大脑轴抑制 ERS 及其随后的小胶质细胞神经炎症。这些发现为未来研究和开发 BHBA 作为 HS 的预防药物奠定了基础，并为通过改变肠道微生物群治疗神经疾病的技术提供了新的见解。
