The mRNA levels of heat shock factor 1 are regulated by thermogenic signals via the cAMP-dependent transcription factor ATF3

Pseudorabies virus UL13 primes inflammatory response through downregulating heat shock factor 1

Pseudorabies virus is a swine alpha-herpesvirus. We demonstrated that alpha-herpesvirus infection downregulates HSF1, a master transcription factor in the heat shock response. The serine/threonine protein kinase activity of late viral protein UL13 is indispensable for HSF1 depletion and phosphorylation, and UL13 does not degrade HSF1 posttranslationally but inhibits the HSF1 mRNA level. Importantly, UL13 increased HSF1 activity even though it reduced HSF1 mRNA. Furthermore, viral replication markedly decreased in the HSF1 knockout cell line or in the presence of an HSF1-specific inhibitor. Interestingly, HSF1 knockout accelerated the activation of NF-κB and p38MAPK. The K96 loci of UL13 are important to induce high levels of IL-6, TNF-α, and IL-β cytokines while playing a crucial role in promoting mild interstitial pneumonia, liver necrosis, and severe inflammatory cell infiltration in the footpad. Thus, UL13 steers the heat shock response to promote viral replication and the inflammatory response. IMPORTANCE: PRV is a ubiquitous pathogen that infects a variety of mammals, such as pigs, ruminants, carnivores, and rodents as well as human beings, causing enormous economic losses in the swine industry. Here, we employed PRV as a model to determine the relationship between α-herpesvirus and the inflammatory response. Overall, our findings indicated that PRV infection inhibits the level of HSF1 mRNA via the serine/threonine protein kinase activity of UL13. Additionally, we discovered that HSF1 was involved in NF-κB activation upon PRV infection. PRV UL13 orchestrates the level of HSF1 mRNA, HSF1 protein phosphorylation, and priming of the inflammatory response. Our study reveals a novel mechanism employed by UL13 serine/threonine protein kinase activity to promote the inflammatory response, providing novel clues for therapy against alpha-herpesvirus infection.

Epigenomic features associated with body temperature stabilize tissues during cold exposure in cold-resistant pigs

Cold stress in low-temperature environments can trigger changes in gene expression, but epigenomics regulation of temperature stability in vital tissues, including the fat and diencephalon, is still unclear. Here, we explore the cold-induced changes in epigenomic features in the diencephalon and fat tissues of two cold-resistant Chinese pig breeds, Min and Enshi black (ES) pigs, utilizing H3K27ac CUT&Tag, RNA-seq, and selective signature analysis. Our results show significant alterations in H3K27ac modifications in the diencephalon of Min pigs and the fat of ES pigs after cold exposure. Dramatic changes in H3K27ac modifications in the diencephalon of Min pig are primarily associated with genes involved in energy metabolism and hormone regulation, whereas those in the fat of ES pig are primarily associated with immunity-related genes. Moreover, transcription factors PRDM1 and HSF1, which show evidence of selection, are enriched in genomic regions presenting cold-responsive alterations in H3K27ac modification in the Min pig diencephalon and ES pig fat, respectively. Our results indicate the diversity of epigenomic response mechanisms to cold exposure between Min and ES pigs, providing unique epigenetic resources for studies of low-temperature adaptation in large mammals.

Hsf1 and Hsf2 in normal, healthy human tissues: Immunohistochemistry provokes new questions

The heat shock transcription factors heat shock transcription factor 1 and Hsf2 have been studied for many years, mainly in the context of stress response and in malignant cells. Their physiological function in nonmalignant human cells under nonstress conditions is still largely unknown. To approach this important issue, Joutsen et al. present immunohistochemical staining data on Hsf1 and Hsf2 in 80 nonpathological human tissue samples. The wealth of these data elicits many interesting questions that will spur many future research projects.

Exploration and biological evaluation of 7-methoxy-3-methyl-1H-chromeno[4,3-c]pyrazol-4-one as an activating transcription factor 3 inducer for managing metabolic syndrome

The induction of activating transcription factor 3 (ATF3) was identified as a promising therapeutic mechanism to overcome metabolic syndrome. Hence, a structure-activity relationship campaign on the chiral lead (1b) was conducted with a scaffold-hopping approach, whereby achiral 7-methoxy-3-methyl-1H-chromeno[4,3-c]pyrazol-4-one (16c) was recognized as a potential ATF3 inducer with a lipid-lowering feature in a pre-differentiated 3T3-L1 cell model. Also, in a high-fat diet scenario, mice subjected to 16c demonstrated robust weight loss with shrinkage of the white adipose mass and fewer hypertrophic adipocytes, accompanied by a preferable glycemic profile compared to 1b. Additionally, the biochemical analysis revealed that 16c further ameliorated the liver function and improved the plasma triglyceride profile that were absent from mice treated with 1b. Taken together, 16c shows promise as an ATF3 stimulant for further development to alleviate metabolic syndrome.

Deregulation of HSF1-mediated endoplasmic reticulum unfolded protein response promotes cisplatin resistance in lung cancer cells

Mild hypothermia can induce apoptotic cell death in many cancer cells, but the underlying mechanisms remain unclear. In a genetic screen in Caenorhabditis elegans, we found that impaired endoplasmic reticulum unfolded protein response (UPR^ER ) increased animal survival after cold shock. Consistently, in normal human lung cells, decreasing culture temperature from 37 to 30 °C activated UPR^ER and promoted cell death. However, lung adenocarcinoma cells were impaired in UPR^ER induction and resistant to hypothermia-induced cell death. Mechanistically, hypothermic stress increased HSF1 levels, which in turn activated UPR^ER to promote apoptotic cell death. HSF1 expression was associated with UPR^ER genes in normal tissues, but such association was lost in many cancers, especially lung adenocarcinoma. Activating UPR^ER enhanced the cytotoxicity of chemotherapy drugs cisplatin preferentially in cancer cells. Consistently, cancer patients with higher UPR^ER expression had generally better prognosis. Together, our study on hypothermia has led to the discovery of HSF1-UPR^ER in the regulation of drug sensitivity in lung cancer cells, providing novel thoughts on developing new strategies against chemoresistance.

HSF1 Can Prevent Inflammation following Heat Shock by Inhibiting the Excessive Activation of the ATF3 and JUN&FOS Genes

Heat Shock Factor 1 (HSF1), a transcription factor frequently overexpressed in cancer, is activated by proteotoxic agents and participates in the regulation of cellular stress response. To investigate how HSF1 level affects the response to proteotoxic stress, we integrated data from functional genomics analyses performed in MCF7 breast adenocarcinoma cells. Although the general transcriptional response to heat shock was impaired due to HSF1 deficiency (mainly chaperone expression was inhibited), a set of genes was identified, including ATF3 and certain FOS and JUN family members, whose stress-induced activation was stronger and persisted longer than in cells with normal HSF1 levels. These genes were direct HSF1 targets, suggesting a dual (activatory/suppressory) role for HSF1. Moreover, we found that heat shock-induced inflammatory response could be stronger in HSF1-deficient cells. Analyses of The Cancer Genome Atlas data indicated that higher ATF3, FOS, and FOSB expression levels correlated with low HSF1 levels in estrogen receptor-positive breast cancer, reflecting higher heat shock-induced expression of these genes in HSF1-deficient MCF7 cells observed in vitro. However, differences between the analyzed cancer types were noted in the regulation of HSF1-dependent genes, indicating the presence of cell-type-specific mechanisms. Nevertheless, our data indicate the existence of the heat shock-induced network of transcription factors (associated with the activation of TNFα signaling) which includes HSF1. Independent of its chaperone-mediated cytoprotective function, HSF1 may be involved in the regulation of this network but prevents its overactivation in some cells during stress.

Inactivation of Type 3 Deiodinase Results in Life-long Changes in the Brown Adipose Tissue Transcriptome in the Male Mouse

Adaptive thermogenesis in small mammals and infants takes place in brown adipose tissue (BAT). Heat is produced via uncoupling protein 1 (UCP1)-mediated uncoupling between oxidation of energy substrates and adenosine 5'-triphosphate synthesis. Thyroid hormone (TH) signaling plays a role in this process. The deiodinases activate thyroxine (T4) to 3,5,3'-triiodothyronine (T3) (D2) or inactivate T4 and T3 to 3,3,5'-triiodothyronine and T2 (D3), respectively. Using a mouse model with selective inactivation of Dio3 in BAT (flox-Dio3 × UCP1-cre = BAT-D3KO), we now show that knocking out D3 resulted in premature exposure of developing brown adipocytes (embryonic days 16.5-18.5) to T3 signaling, leading to an earlier expression of key BAT genes, including Cidea, Cox8b, Dio2, Ucp1, and Pgc1α. Adult BAT-D3KO mice exhibited increased expression of 1591 genes as assessed by RNA sequencing, including 19 gene sets related to mitochondria, 8 related to fat, and 8 related to glucose homeostasis. The expression of 243 genes was changed by more than 1.5-fold, 36 of which play a role in metabolic/thermogenic processes. BAT-D3KO mice weigh less and exhibit smaller white adipocyte area, but maintain normal energy expenditure at room temperature (22 °C) and in the cold (4 °C). They also defend their core temperature more effectively and do not lose as much body weight when exposed to cold. We conclude that the coordinated actions of Dio3 in the embryonic BAT define the timing and intensity of T3 signaling during brown adipogenesis. Enhanced T3 signaling during BAT embryogenesis (Dio3 inactivation) results in selective life-long modifications in the BAT transcriptome.

The ATF3 inducer protects against diet-induced obesity via suppressing adipocyte adipogenesis and promoting lipolysis and browning

In this study, we investigated whether the activating transcription factor 3 (ATF3) inducer ST32db, a synthetic compound with a chemical structure similar to that of native Danshen compounds, exerts an anti-obesity effect in 3T3-L1 white preadipocytes, D16 beige cells, and mice with obesity induced by a high-fat diet (HFD). The results showed that ST32db inhibited 3T3-L1 preadipocyte differentiation by inhibiting adipogenesis/lipogenesis-related gene (and protein levels) and enhancing lipolysis-related gene (and protein levels) via the activation of β3-adrenoceptor (β3-AR)/PKA/p38, AMPK, and ERK pathways. Furthermore, ST32db inhibited triacylglycerol accumulation in D16 adipocytes by suppressing adipogenesis/lipogenesis-related gene (and protein levels) and upregulating browning gene expression by suppressing the β3-AR/PKA/p38, and AMPK pathways. Intraperitoneally injected ST32db (1 mg kg-1 twice weekly) inhibited body weight gain and reduced the weight of inguinal white adipose tissue (iWAT), epididymal WAT (eWAT), and mesenteric WAT, with no effects on food intake by the obese mice. The adipocyte diameter and area of iWAT and eWAT were decreased in obese mice injected with ST32db compared with those administered only HFD. In addition, ST32db significantly suppressed adipogenesis and activated lipolysis, browning, mitochondrial oxidative phosphorylation, and β-oxidation-related pathways by suppressing the p38 pathway in the iWAT of the obese mice. These results indicated that the ATF3 inducer ST32db has therapeutic potential for reducing obesity.

ADH5-mediated NO bioactivity maintains metabolic homeostasis in brown adipose tissue

Brown adipose tissue (BAT) thermogenic activity is tightly regulated by cellular redox status, but the underlying molecular mechanisms are incompletely understood. Protein S-nitrosylation, the nitric-oxide-mediated cysteine thiol protein modification, plays important roles in cellular redox regulation. Here we show that diet-induced obesity (DIO) and acute cold exposure elevate BAT protein S-nitrosylation, including UCP1. This thermogenic-induced nitric oxide bioactivity is regulated by S-nitrosoglutathione reductase (GSNOR; alcohol dehydrogenase 5 [ADH5]), a denitrosylase that balances the intracellular nitroso-redox status. Loss of ADH5 in BAT impairs cold-induced UCP1-dependent thermogenesis and worsens obesity-associated metabolic dysfunction. Mechanistically, we demonstrate that Adh5 expression is induced by the transcription factor heat shock factor 1 (HSF1), and administration of an HSF1 activator to BAT of DIO mice increases Adh5 expression and significantly improves UCP1-mediated respiration. Together, these data indicate that ADH5 controls BAT nitroso-redox homeostasis to regulate adipose thermogenesis, which may be therapeutically targeted to improve metabolic health.

Browning of adipose tissue and increased thermogenesis induced by Methotrexate

Methotrexate (MTX) is widely used for the treatment of rheumatoid arthritis due to its well-known anti-inflammatory role in immune cells but its impact on brown and beige adipose tissue biology has not yet been investigated. Here, we present the novel evidence that MTX treatment increases the gene expression of thermogenic genes in brown and beige adipose tissues in a fat cell autonomous manner. Furthermore, we show that treatment of mice with MTX is associated with cold resistance, improved glucose homeostasis, decreased inflammation, and reduced hepatosteatosis in high-fat diet states. Overall, our data provide novel evidence of a role of MTX on thermogenic tissues not previously appreciated.

The Forkhead Box Transcription Factor FoxP4 Regulates Thermogenic Programs in Adipocytes

Forkhead box transcription factors have been shown to be involved in various developmental and differentiation processes. In particular, members of the FoxP family have been previously characterized in depth for their participation in the regulation of lung and neuronal cell differentiation and T-cell development and function; however, their role in adipocyte functionality has not yet been investigated. Here, we report for the first time that Forkhead box P4 (FoxP4) is expressed at high levels in subcutaneous fat depots and mature thermogenic adipocytes. Through molecular and gene expression analyses, we revealed that FoxP4 is induced in response to thermogenic stimuli, both in vivo and in isolated cells, and is regulated directly by the heat shock factor protein 1 through a heat shock response element identified in the proximal promoter region of FoxP4. Further detailed analysis involving chromatin immunoprecipitation and luciferase assays demonstrated that FoxP4 directly controls the levels of uncoupling protein 1, a key regulator of thermogenesis that uncouples fatty acid oxidation from ATP production. In addition, through our gain-of-function and loss-of-function studies, we showed that FoxP4 regulates the expression of a number of classic brown and beige fat genes and affects oxygen consumption in isolated adipocytes. Overall, our data demonstrate for the first time the novel role of FoxP4 in the regulation of thermogenic adipocyte functionality.

ReporterSeq reveals genome-wide dynamic modulators of the heat shock response across diverse stressors

Understanding cellular stress response pathways is challenging because of the complexity of regulatory mechanisms and response dynamics, which can vary with both time and the type of stress. We developed a reverse genetic method called ReporterSeq to comprehensively identify genes regulating a stress-induced transcription factor under multiple conditions in a time-resolved manner. ReporterSeq links RNA-encoded barcode levels to pathway-specific output under genetic perturbations, allowing pooled pathway activity measurements via DNA sequencing alone and without cell enrichment or single-cell isolation. We used ReporterSeq to identify regulators of the heat shock response (HSR), a conserved, poorly understood transcriptional program that protects cells from proteotoxicity and is misregulated in disease. Genome-wide HSR regulation in budding yeast was assessed across 15 stress conditions, uncovering novel stress-specific, time-specific, and constitutive regulators. ReporterSeq can assess the genetic regulators of any transcriptional pathway with the scale of pooled genetic screens and the precision of pathway-specific readouts.

PPARγ agonists delay age-associated metabolic disease and extend longevity

Aging leads to a number of disorders caused by cellular senescence, tissue damage, and organ dysfunction. It has been reported that anti‐inflammatory and insulin‐sensitizing compounds delay, or reverse, the aging process and prevent metabolic disorders, neurodegenerative disease, and muscle atrophy, improving healthspan and extending lifespan. Here we investigated the effects of PPARγ agonists in preventing aging and increasing longevity, given their known properties in lowering inflammation and decreasing glycemia. Our molecular and physiological studies show that long‐term treatment of mice at 14 months of age with low doses of the PPARγ ligand rosiglitazone (Rosi) improved glucose metabolism and mitochondrial functionality. These effects were associated with decreased inflammation and reduced tissue atrophy, improved cognitive function, and diminished anxiety‐ and depression‐like conditions, without any adverse effects on cardiac and skeletal functionality. Furthermore, Rosi treatment of mice started when they were 14 months old was associated with lifespan extension. A retrospective analysis of the effects of the PPARγ agonist pioglitazone (Pio) on longevity showed decreased mortality in patients receiving Pio compared to those receiving a PPARγ‐independent insulin secretagogue glimepiride. Taken together, these data suggest the possibility of using PPARγ agonists to promote healthy aging and extend lifespan.

Emerging roles of HSF1 in cancer: Cellular and molecular episodes

Heat shock factor 1 (HSF1) systematically guards proteome stability and proteostasis by regulating the expression of heat shock protein (HSP), thus rendering cancer cells addicted to HSF1. The non-canonical transcriptional programme driven by HSF1, which is distinct from the heat shock response (HSR), plays an indispensable role in the initiation, promotion and progression of cancer. Therefore, HSF1 is widely exploited as a potential therapeutic target in a broad spectrum of cancers. Various molecules and signals in the cell jointly regulate the activation and attenuation of HSF1. The high-level expression of HSF1 in tumours and its relationship with patient prognosis imply that HSF1 can be used as a biomarker for patient prognosis and a target for cancer treatment. In this review, we discuss the newly identified mechanisms of HSF1 activation and regulation, the diverse functions of HSF1 in tumourigenesis, and the feasibility of using HSF1 as a prognostic marker. Disrupting cancer cell proteostasis by targeting HSF1 represents a novel anti-cancer therapeutic strategy.