N-butyrate increases heat shock protein 70 through heat shock factor 1 and AMP-activated protein kinase pathways in human intestinal Caco-2 cells.

Impaired integrity of the intestinal epithelium is a cause of intestinal and extraintestinal diseases. Heat shock protein 70 (HSP70), a cytoprotective protein, plays an important role in maintaining intestinal homeostasis. The intestinal expression of HSP70 is linked with the local microbiota. The present study investigated the molecular mechanisms underlying the upregulation of HSP70 by n-butyrate, a major metabolite of the intestinal microbiota in human intestinal Caco-2 cells. Treatment of Caco-2 cells with n-butyrate upregulated HSP70 protein and mRNA levels in a dose-dependent manner. Using luciferase reporter assay, it was found that n-butyrate enhanced the transcriptional activity of HSP70. These effects were sensitive to the inhibition of heat shock factor 1 (HSF1), a transcription factor, and AMP-activated protein kinase (AMPK). N-butyrate increased the phosphorylation (activity) of HSF1 and AMPK. Taken together, this study shows that n-butyrate is partly involved in the microbiota-dependent intestinal expression of HSP70, and the effect is exerted through the HSF1 and AMPK pathways.

HSF1 Alleviates Brain Injury by Inhibiting NLRP3-Induced Pyroptosis in a Sepsis Model.

Background: Sepsis, which could cause a systemic inflammatory response, is a life-threatening disease with a high morbidity and mortality rate. There is evidence that brain injury may be related to severe systemic infection induced by sepsis. The brain injury caused by sepsis could increase the risk of mortality in septic patients, which seriously affects the septic patient's prognosis of survival. Although there remains a focus on sepsis research, clinical measures to prevent and treat brain injury in sepsis are not yet available, and the high mortality rate is still a big health burden. Therefore, it is necessary to investigate the new molecules or regulated pathways that can effectively inhibit the progress of sepsis. Objective: NLR family pyrin domain-containing 3 (NLRP3) increased in the procession of sepsis and functioned as the key regulator of pyroptosis. Heat shock factor 1 (HSF1) can protect organs from multiorgan dysfunction syndrome induced by lipopolysaccharides in mice, and NLRP3 could be inhibited by HSF1 in many organs. However, whether HSF1 regulated NLRP3 in sepsis-induced brain injury, as well as the detailed mechanism of HSF1 in brain injury, remains unknown in the sepsis model. In this research, we try to explore the relationship between HSF1 and NLRP3 in a sepsis model and try to reveal the mechanism of HSF1 inhibiting the process of brain injury. Methods: In this study, we used wild-type mice and hsf1 -/- mice for in vivo research and PC12 cells for in vitro research. Real-time PCR and Western blot were used to analyze the expression of HSF1, NLRP3, cytokines, and pyrolytic proteins. EthD-III staining was chosen to detect the pyroptosis of the hippocampus and PC12 cells. Results: The results showed that HSF1 is negatively related to pyroptosis. The pyroptosis in cells of brain tissue was significantly increased in the hsf1 -/- mouse model compared to hsf1 +/+ mice. In PC12 cells, hsf1 siRNA can upregulate pyroptosis while HSF1-transfected plasmid could inhibit the pyroptosis. HSF1 could negatively regulate the NLRP3 pathway in PC12 cells, while hsf1 siRNA enhanced the pyroptosis in PC12 cells, which could be reversed by nlrp3 siRNA. Conclusion: These results imply that HSF1 could alleviate sepsis-induced brain injury by inhibiting pyroptosis through the NLRP3-dependent pathway in brain tissue and PC12 cells, suggesting HSF1 as a potential molecular target for treating brain injury in sepsis clinical studies.

PHLDA1 Does Not Contribute Directly to Heat Shock-Induced Apoptosis of Spermatocytes.

Spermatocytes are among the most heat-sensitive cells and the exposure of testes to heat shock results in their Heat Shock Factor 1 (HSF1)-mediated apoptosis. Several lines of evidence suggest that pleckstrin-homology-like domain family A, member 1 (PHLDA1) plays a role in promoting heat shock-induced cell death in spermatogenic cells, yet its precise physiological role is not well understood. Aiming to elucidate the hypothetical role of PHLDA1 in HSF1-mediated apoptosis of spermatogenic cells we characterized its expression in mouse testes during normal development and after heat shock. We stated that transcription of Phlda1 is upregulated by heat shock in many adult mouse organs including the testes. Analyzes of the Phlda1 expression during postnatal development indicate that it is expressed in pre-meiotic or somatic cells of the testis. It starts to be transcribed much earlier than spermatocytes are fully developed and its transcripts and protein products do not accumulate further in the later stages. Moreover, neither heat shock nor expression of constitutively active HSF1 results in the accumulation of PHLDA1 protein in meiotic and post-meiotic cells although both conditions induce massive apoptosis of spermatocytes. Furthermore, the overexpression of PHLDA1 in NIH3T3 cells leads to cell detachment, yet classical apoptosis is not observed. Therefore, our findings indicate that PHLDA1 cannot directly contribute to the heat-induced apoptosis of spermatocytes. Instead, PHLDA1 could hypothetically participate in death of spermatocytes indirectly via activation of changes in the somatic or pre-meiotic cells present in the testes.

HSF1 inhibits microglia activation to attenuate neuroinflammation via regulating miR-214-3p and NFATc2 in Parkinson's disease.

Parkinson's disease (PD) is characterized by microglia activation that leads to neuroinflammation. Heat shock transcription factor 1 (HSF1) is known to exert neuroprotective effects on neurodegenerative diseases. This study sought to analyse the role and mechanism of HSF1 in PD-induced neuroinflammation. The PD mouse models were established using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Animal behaviour capacities and neuronal damage were assessed via behavioural tests, tyrosine hydroxylase (TH) staining, and immunofluorescence. Levels of HSF1, miR-214-3p, nuclear factor of activated T cells 2 (NFATc2), and neuroinflammatory factors were detected via RT-qPCR, Western blotting, and ELISA.Binding relationships between HSF1 and miR-214-3p, miR-214-3p, and NFATc2 were tested via dual-luciferase or chromatin immunoprecipitation assays. Functional rescue experiments were designed to confirm the roles of miR-214-3p and NFATc2. HSF1 expression in brain tissues was downregulated upon MPTP treatment. HSF1 overexpression reduced motor deficits and loss of dopaminergic neurons, increased TH-positive neurons, and repressed neuroinflammation and micro-glia activation. Mechanically, HSF1 bound to the miR-214-3p promoter to increase its expression and inhibited NFATc2 transcription. miR-214-3p downregulation or NFATc2 overexpression reversed the inhibition of HSF1 overexpression on neuroinflammation and microglia activation. Overall, our findings unveiled the therapeutic role of HSF1 in PD-induced neuroinflammation and microglia activation via regulating miR-214-3p and NFATc2.