Methylene blue increases the amount of HSF1 through promotion of PKA-mediated increase in HSF1-p300 interaction

BAP1 regulates HSF1 activity and cancer immunity in pancreatic cancer

BACKGROUND

The vast majority of pancreatic cancers have been shown to be insensitive to single-agent immunotherapy. Exploring the mechanisms of immune resistance and implementing combination therapeutic strategies are crucial for PDAC patients to derive benefits from immunotherapy. Deletion of BAP1 occurs in approximately 27% of PDAC patients and is significantly correlated with poor prognosis, but the mechanism how BAP1-deletion compromises survival of patients with PDAC remain a puzzle.

METHODS

Bap1 knock-out KPC (KrasG12D/+; LSLTrp53R172H/+; Pdx-1-Cre) mice and control KPC mice, syngeneic xenograft models were applied to analysis the correlation between BAP1 and immune therapy response in PDAC. Immunoprecipitation, RT-qPCR, luciferase and transcriptome analysis were combined to revealing potential mechanisms. Syngeneic xenograft models and flow cytometry were constructed to examine the efficacy of the inhibitor of SIRT1 and its synergistic effect with anti-PD-1 therapy.

RESULT

The deletion of BAP1 contributes to the resistance to immunotherapy in PDAC, which is attributable to BAP1's suppression of the transcriptional activity of HSF1. Specifically, BAP1 competes with SIRT1 for binding to the K80 acetylated HSF1. The BAP1-HSF1 interaction preserves the acetylation of HSF1-K80 and promotes HSF1-HSP70 interaction, facilitating HSF1 oligomerization and detachment from the chromatin. Furthermore, we demonstrate that the targeted inhibition of SIRT1 reverses the immune insensitivity in BAP1 deficient PDAC mouse model.

CONCLUSION

Our study elucidates an unrevealed mechanism by which BAP1 regulates immune therapy response in PDAC via HSF1 inhibition, and providing promising therapeutic strategies to address immune insensitivity in BAP1-deficient PDAC.

Hyperhomocysteinemia activates NLRP3 inflammasome to cause hepatic steatosis and insulin resistance via MDM2-mediated ubiquitination of HSF1

Hyperhomocysteinemia (HHcy) is associated with nonalcoholic fatty liver disease (NAFLD) and insulin resistance (IR). However, the underlying mechanism is still unknown. Recent studies have demonstrated that NLRP3 inflammasome activation plays a vital role in NAFLD and IR. Our study aimed to explore whether NLRP3 inflammasome contributed to HHcy-induced NAFLD and IR as well as dissected the underlying mechanism. C57BL/6 mice were fed a high-methionine diet (HMD) for 8 weeks to establish the HHcy mouse model. Compared with a chow diet, HMD induced hepatic steatosis (HS) and IR as well as activation of hepatic NLRP3 inflammasome. Moreover, HHcy-induced NAFLD and IR characterization disclosed that NLRP3 inflammasome activation occurred in liver tissue of HMD-fed mice, but was very marginal in either NLRP3^-/- or Caspase-1^-/- mice. Mechanistically, high levels of homocysteine (Hcy) up-regulated the expression of mouse double minute 2 homolog (MDM2), which directly ubiquitinates heat shock transcription factor 1 (HSF1) and consequently activated hepatic NLRP3 inflammasome in vivo and in vitro. In addition, in vitro experiments showed P300-mediated HSF1 acetylation at K298 hindered MDM2-mediated ubiquitination of HSF1 at K372, which plays important role in determining the HSF1 level. Importantly, either inhibition of MDM2 by JNJ-165 or activation of HSF1 by HSF1A reversed HMD-induced hepatic NLRP3 inflammasome, and consequently alleviated HS and IR in mice. This study demonstrates that NLRP3 inflammasome activation contributes to HHcy-induced NAFLD and IR, and further identified that HSF1 as a new substrate of MDM2 and its decrease on MDM2-mediated ubiquitination at K372 modulates NLRP3 inflammasome activation. These findings may provide novel therapeutic strategies aimed at halting HS or IR.

Molecular mechanisms of heat shock factor 1 regulation

To thrive and to fulfill their functions, cells need to maintain proteome homeostasis even in the face of adverse environmental conditions or radical restructuring of the proteome during differentiation. At the center of the regulation of proteome homeostasis is an ancient transcriptional mechanism, the so-called heat shock response (HSR), orchestrated in all eukaryotic cells by heat shock transcription factor 1 (Hsf1). As Hsf1 is implicated in aging and several pathologies like cancer and neurodegenerative disorders, understanding the regulation of Hsf1 could open novel therapeutic opportunities. In this review, we discuss the regulation of Hsf1's transcriptional activity by multiple layers of control circuits involving Hsf1 synthesis and degradation, conformational rearrangements and post-translational modifications (PTMs), and molecular chaperones in negative feedback loops.

Demonstrated hormetic mechanisms putatively subserve riluzole-induced effects in neuroprotection against amyotrophic lateral sclerosis (ALS): Implications for research and clinical practice

This paper provides evidence to support that riluzole, an FDA-approved treatment for amyotrophic lateral sclerosis (ALS), like many neuroprotective agents, displays and exerts hormetic biphasic dose responses. These findings have important implications for the experimental study and clinical treatment of ALS.

Hsp70 inhibitors: Implications for the treatment of colorectal cancer

Colorectal cancer (CRC) is one of the most common malignancies in the world. Despite intensive advances in diagnosis and treatment of CRC, it is yet one of the leading cause of cancer related morbidity and mortality. Therefore, there is an urgent medical need for alternative therapeutic approaches to treat CRC. The 70 kDa heat shock proteins (Hsp70s) are a family of evolutionary conserved heat shock proteins, which play an important role in cell homeostasis and survival. They overexpress in various types of malignancy including CRC and are typically accompanied with poor prognosis. Hence, inhibition of Hsp70 may be considered as a striking chemotherapeutic avenue. This review summarizes the current knowledge on the progress made so far to discover compounds, which target the Hsp70 family, with particular emphasis on their efficacy in treatment of CRC. We also briefly explain the induction of Hsp70 as a strategy to prevent CRC.

Regulation of HSF1 protein stabilization: An updated review

Heat shock factor 1 (HSF1) is a transcriptional factor that determines the efficiency of heat shock responses (HSRs) in the cell. Given its function has been extensively studied in recent years, HSF1 is considered a potential target for the treatment of disorders associated with protein aggregation. The activity of HSF1 is traditionally regulated at the transcriptional level in which the transactivation domain of HSF1 is modified by extensive array of pos-translational modifications, such as phosphorylation, sumoylation, and acetylation. Recently, HSF1 is also reported to be regulated at the monomeric level. For example, in neurodegenerative disorders such as Huntington's disease and Alzheimer's disease the expression levels of the monomeric HSF1 are found to be reduced markedly. Methylene blue (MB) and riluzole, two clinical available drugs, increase the amount of the monomeric HSF1 in both cells and animals. Since the monomeric HSF1 not only determines the efficiency of HSRs, but exerts protective effects in a trimerization-independent manner, increasing the amount of the monomeric HSF1 via stabilization of HSF1 may be an alternative strategy for the amplification of HSR. However, to date we have no outlined knowledges about HSF1 protein stabilization, though studies regarding the regulation of the monomeric HSF1 have been documented in recent years. Here, we summarize the regulation of the monomeric HSF1 by some previously reported factors, such as synuclein, Huntingtin (Htt), TDP-43, unfolded protein response (UPR), MB and doxorubicin (DOX), as well as their possible mechanisms, aiming to push the understanding about HSF1 protein stabilization.

Harmine produces antidepressant-like effects via restoration of astrocytic functions

Depression is a world-wide disease with no effective therapeutic methods. Increasing evidence indicates that astrocytic pathology contributes to the formation of depression. In this study, we investigated the effects of harmine, a natural β-carboline alkaloid and potent hallucinogen, known to modulate astrocytic glutamate transporters, on chronic unpredictable stress (CUS)-induced depressive-like behaviors and astrocytic dysfunctions. Results showed that harmine treatment (10, 20mg/kg) protected the mice against the CUS-induced increases in the immobile time in the tail suspension test (TST) and forced swimming test (FST), and also reversed the reduction in sucrose intake in the sucrose preference experiment. Harmine treatment (20mg/kg) prevented the reductions in brain-derived neurotrophic factor (BDNF) protein levels and hippocampal neurogenesis induced by CUS. In addition, harmine treatment (20mg/kg) increased the protein expression levels of glutamate transporter 1 (GLT-1) and prevented the CUS-induced decreases in glial fibrillary acidic protein (GFAP) protein expressions in the prefrontal cortex and hippocampus, suggesting that restoration of astrocytic functions may be a potential mechanism underlying the antidepressant-like effects of harmine. This opinion was proved by the results that administration of mice with l-Alpha-Aminoadipic Acid (L-AAA), a gliotoxin specific for astrocytes, attenuated the antidepressant-like effects of harmine, and prevented the improvement effects of harmine on BDNF protein levels and hippocampal neurogenesis. These results provide further evidence to confirm that astrocytic dysfunction contributes critically to the development of depression and that harmine exerts antidepressant-like effects likely through restoration of astrocytic functions.