Regulatory coordination between two major intracellular homeostatic systems: heat shock response and autophagy

The biphasic activity of autophagy and heat shock protein response in peripheral blood mononuclear cells following acute resistance exercise in resistance-trained males

PURPOSE

Autophagy and heat shock protein (HSP) response are proteostatic systems involved in the acute and adaptive responses to exercise. These systems may upregulate sequentially following cellular stress including acute exercise, however, currently few data exist in humans. This study investigated the autophagic and HSP responses to acute intense lower body resistance exercise in peripheral blood mononuclear cells (PBMCs) with and without branched-chain amino acids (BCAA) supplementation.

METHODS

Twenty resistance-trained males (22.3 ± 1.5 yr; 175.4 ± .7 cm; 86.4 ± 15.6 kg) performed a bout of intense lower body resistance exercise and markers of autophagy and HSP70 were measured immediately post- (IPE) and 2, 4, 24, 48, and 72 h post-exercise. Prior to resistance exercise, 10 subjects were randomly assigned to BCAA supplementation of 0.22 g/kg/d for 5 days pre-exercise and up to 72 h following exercise while the other 10 subjects consumed a placebo (PLCB).

RESULTS

There were no difference in autophagy markers or HSP70 expression between BCAA and PLCB groups. LC3II protein expression was significantly lower 2 and 4 h post-exercise compared to pre-exercise. LC3II: I ratio was not different at any time point compared to pre-exercise. Protein expression of p62 was lower IPE, 2, and 4 h post-exercise and elevated 24 h post-exercise. HSP70 expression was elevated 48 and 72 h post-exercise.

CONCLUSIONS

Autophagy and HSP70 are upregulated in PBMCs following intense resistance exercise with autophagy increasing initially post-exercise and HSP response in the latter period. Moreover, BCAA supplementation did not affect this response.

Hsp70 Negatively Regulates Autophagy via Governing AMPK Activation, and Dual Hsp70-Autophagy Inhibition Induces Synergetic Cell Death in NSCLC Cells

Proteostasis mechanisms, such as proteotoxic-stress response and autophagy, are increasingly recognized for their roles in influencing various cancer hallmarks such as tumorigenesis, drug resistance, and recurrence. However, the precise mechanisms underlying their coordination remain not fully elucidated. The aim of this study is to investigate the molecular interplay between Hsp70 and autophagy in lung adenocarcinoma cells and elucidate its impact on the outcomes of anticancer therapies in vitro. For this purpose, we utilized the human lung adenocarcinoma A549 cell line and genetically modified it by knockdown of Hsp70 or HSF1, and the H1299 cell line with knockdown or overexpression of Hsp70. In addition, several treatments were employed, including treatment with Hsp70 inhibitors (VER-155008 and JG-98), HSF1 activator ML-346, or autophagy modulators (SAR405 and Rapamycin). Using immunoblotting, we found that Hsp70 negatively regulates autophagy by directly influencing AMPK activation, uncovering a novel regulatory mechanism of autophagy by Hsp70. Genetic or chemical Hsp70 overexpression was associated with the suppression of AMPK and autophagy. Conversely, the inhibition of Hsp70, genetically or chemically, resulted in the upregulation of AMPK-mediated autophagy. We further investigated whether Hsp70 suppression-mediated autophagy exhibits pro-survival- or pro-death-inducing effects via MTT test, colony formation, CellTiter-Glo 3D-Spheroid viability assay, and Annexin/PI apoptosis assay. Our results show that combined inhibition of Hsp70 and autophagy, along with cisplatin treatment, synergistically reduces tumor cell metabolic activity, growth, and viability in 2D and 3D tumor cell models. These cytotoxic effects were exerted by substantially potentiating apoptosis, while activating autophagy via rapamycin slightly rescued tumor cells from apoptosis. Therefore, our findings demonstrate that the combined inhibition of Hsp70 and autophagy represents a novel and promising therapeutic approach that may disrupt the capacity of refractory tumor cells to withstand conventional therapies in NSCLC.

Effect of daylong exposure to indoor overheating on autophagy and the cellular stress response in older adults

To protect vulnerable populations during heat waves, public health agencies recommend maintaining indoor air temperature below ∼24-28 °C. While we recently demonstrated that maintaining indoor temperatures ≤26 °C mitigates the development of hyperthermia and cardiovascular strain in older adults, the cellular consequences of prolonged indoor heat stress are poorly understood. We therefore evaluated the cellular stress response in 16 adults (six females) aged 66-78 years during 8 h rest in ambient conditions simulating homes maintained at 22 °C (control) and 26 °C (indoor temperature upper limit proposed by health agencies), as well as non-air-conditioned domiciles during hot weather and heat waves (31 and 36 °C, respectively; all 45% relative humidity). Western blot analysis was used to assess changes in proteins associated with the cellular stress response (autophagy, apoptosis, acute inflammation, and heat shock proteins) in peripheral blood mononuclear cells harvested prior to and following exposure. Following 8 h exposure, no cellular stress response-related proteins differed significantly between the 26 and 22 °C conditions (all, P ≥ 0.056). By contrast, autophagy-related proteins were elevated following exposure to 31 °C (p62: 1.5-fold; P = 0.003) and 36 °C (LC3-II, LC3-II/I, p62; all ≥2.0-fold; P ≤ 0.002) compared to 22 °C. These responses were accompanied by elevations in apoptotic signaling in the 31 and 36 °C conditions (cleaved-caspase-3: 1.8-fold and 3.7-fold, respectively; P ≤ 0.002). Furthermore, HSP90 was significantly reduced in the 36 °C compared to 22 °C condition (0.7-fold; P = 0.014). Our findings show that older adults experience considerable cellular stress during prolonged exposure to elevated ambient temperatures and support recommendations to maintain indoor temperatures ≤26 °C to prevent physiological strain in heat-vulnerable persons.

Bronchial thermoplasty decreases airway remodeling by inhibiting autophagy via the AMPK/mTOR signaling pathway

Bronchial thermoplasty (BT), an effective treatment for severe asthma, requires heat to reach the airway to reduce the mass of airway smooth muscle cells (ASMCs). Autophagy is involved in the pathological process of airway remodeling in patients with asthma. However, it remains unclear whether autophagy participates in controlling airway remodeling induced by BT. In this study, we aim to elucidate the autophagy-mediated molecular mechanisms in BT. Our study reveal that the number of autophagosomes and the level of alpha-smooth muscle actin (α-SMA) fluorescence are significantly decreased in airway biopsy tissues after BT. As the temperature increased, BT causes a decrease in cell proliferation and a concomitant increase in the apoptosis of human airway smooth muscle cells (HASMCs). Furthermore, increase in temperature significantly downregulates cellular autophagy, autophagosome accumulation, the LC3II/LC3I ratio, and Beclin-1 expression, upregulates p62 expression, and inhibits the AMPK/mTOR pathway. Furthermore, cotreatment with AICAR (an AMPK agonist) or RAPA (an mTOR antagonist) abolishes the inhibition of autophagy and attenuates the increase in the apoptosis rate of HASMCs induced by the thermal effect. Therefore, we conclude that BT decreases airway remodeling by blocking autophagy induced by the AMPK/mTOR signaling pathway in HASMCs.

Natural variation in Brachypodium distachyon responses to combined abiotic stresses

The demand for agricultural production is becoming more challenging as climate change increases global temperature and the frequency of extreme weather events. This study examines the phenotypic variation of 149 accessions of Brachypodium distachyon under drought, heat, and the combination of stresses. Heat alone causes the largest amounts of tissue damage while the combination of stresses causes the largest decrease in biomass compared to other treatments. Notably, Bd21-0, the reference line for B. distachyon, did not have robust growth under stress conditions, especially the heat and combined drought and heat treatments. The climate of origin was significantly associated with B. distachyon responses to the assessed stress conditions. Additionally, a GWAS found loci associated with changes in plant height and the amount of damaged tissue under stress. Some of these SNPs were closely located to genes known to be involved in responses to abiotic stresses and point to potential causative loci in plant stress response. However, SNPs found to be significantly associated with a response to heat or drought individually are not also significantly associated with the combination of stresses. This, with the phenotypic data, suggests that the effects of these abiotic stresses are not simply additive, and the responses to the combined stresses differ from drought and heat alone.

Temperature-Dependent Relationship of Autophagy and Apoptotic Signaling During Cold-Water Immersion in Young and Older Males

Autophagy is a crucial cytoprotective mechanism preventing the accumulation of cellular damage, especially during external stimuli such as cold exposure. Older adults poorly tolerate cold exposure and age-related impairments in autophagy may contribute to the associated reductions in cold tolerance. The purpose of this investigation is to evaluate the effect of different intensities of in vivo cold-water immersion and in vitro cold exposure on autophagic and apoptotic signaling in young and older males. Peripheral blood mononuclear cells (PBMCs) are isolated at baseline, end-cold exposure, and after 3 h of thermoneutral recovery. Additionally, PBMCs are treated with rapamycin and bafilomycin prior to in vitro cold exposure equivalent to in vivo core temperatures (35-37 °C). Proteins associated with autophagy, apoptosis, the heat shock response, and inflammation are analyzed via Western blotting. Moderate cold stress (0.5 °C decrease in core temperature) increased autophagic and heat shock protein activity while high cold stress (1.0 °C decrease in core temperature) augmented apoptosis in young males. In older males, minimal autophagic activation during both cold-water exposures are associated with increased apoptotic and inflammatory proteins. Although in vitro cold exposure confirmed age-related dysfunction in autophagy, rapamycin-induced stimulation of autophagic proteins underlie the potential to reverse age-related vulnerability to cold exposure.

Autophagy and oxidative stress modulation mediate Bortezomib resistance in prostate cancer

Proteasome inhibitors such as Bortezomib represent an established type of targeted treatment for several types of hematological malignancies, including multiple myeloma, Waldenstrom's macroglobulinemia, and mantle cell lymphoma, based on the cancer cell's susceptibility to impairment of the proteasome-ubiquitin system. However, a major problem limiting their efficacy is the emergence of resistance. Their application to solid tumors is currently being studied, while simultaneously, a wide spectrum of hematological cancers, such as Myelodysplastic Syndromes show minimal or no response to Bortezomib treatment. In this study, we utilize the prostate cancer cell line DU-145 to establish a model of Bortezomib resistance, studying the underlying mechanisms. Evaluating the resulting resistant cell line, we observed restoration of proteasome chymotrypsin-like activity, regardless of drug presence, an induction of pro-survival pathways, and the substitution of the Ubiquitin-Proteasome System role in proteostasis by induction of autophagy. Finally, an estimation of the oxidative condition of the cells indicated that the resistant clones reduce the generation of reactive oxygen species induced by Bortezomib to levels even lower than those induced in non-resistant cells. Our findings highlight the role of autophagy and oxidative stress regulation in Bortezomib resistance and elucidate key proteins of signaling pathways as potential pharmaceutical targets, which could increase the efficiency of proteasome-targeting therapies, thus expanding the group of molecular targets for neoplastic disorders.

Harnessing Hyperthermia: Molecular, Cellular, and Immunological Insights for Enhanced Anticancer Therapies

Hyperthermia, the raising of tumor temperature (≥39°C), holds great promise as an adjuvant treatment for cancer therapy. This review focuses on 2 key aspects of hyperthermia: its molecular and cellular effects and its impact on the immune system. Hyperthermia has profound effects on critical biological processes. Increased temperatures inhibit DNA repair enzymes, making cancer cells more sensitive to chemotherapy and radiation. Elevated temperatures also induce cell cycle arrest and trigger apoptotic pathways. Furthermore, hyperthermia modifies the expression of heat shock proteins, which play vital roles in cancer therapy, including enhancing immune responses. Hyperthermic treatments also have a significant impact on the body's immune response against tumors, potentially improving the efficacy of immune checkpoint inhibitors. Mild systemic hyperthermia (39°C-41°C) mimics fever, activating immune cells and raising metabolic rates. Intense heat above 50°C can release tumor antigens, enhancing immune reactions. Using photothermal nanoparticles for targeted heating and drug delivery can also modulate the immune response. Hyperthermia emerges as a cost-effective and well-tolerated adjuvant therapy when integrated with immunotherapy. This comprehensive review serves as a valuable resource for the selection of patient-specific treatments and the guidance of future experimental studies.

The intensity-dependent effects of exercise and superimposing environmental heat stress on autophagy in peripheral blood mononuclear cells from older men

Autophagy is a vital cellular process, essential to maintaining cellular function during acute physiological stressors including exercise and heat stress. We previously showed that autophagy occurs during exercise in an intensity-dependent manner in peripheral blood mononuclear cells (PBMCs) from young men, with elevated responses in the heat. However, given autophagy declines with age, it is unclear whether a similar pattern of response occurs in older adults. Therefore, we evaluated autophagy and the cellular stress response [i.e., apoptosis, inflammation, and the heat shock response (HSR)] in PBMCs from 10 healthy older men [mean (SD): aged 70 yr (5)] in response to 30 min of semirecumbent cycling at low, moderate, and vigorous intensities [40, 55, and 70% maximal oxygen consumption (V̇o2max), respectively] in a temperate (25°C) environment, with an additional vigorous-intensity bout (70% of V̇o2max) performed in a hot environment (40°C). Responses were evaluated before and after exercise, as well as throughout a 6-h seated recovery period performed in the same environmental conditions as the respective exercise bout. Proteins were assessed via Western blot. Although we observed elevations in mean body temperature with each increase in exercise intensity, autophagy was only stimulated during vigorous-intensity exercise, where we observed elevations in LC3-II (P < 0.05). However, when the same exercise was performed in the heat, the LC3-II response was attenuated, which was accompanied by significant p62 accumulation (P < 0.05). Altogether, our findings demonstrate that older adults exhibit autophagic impairments when the same vigorous-intensity exercise is performed in hot environments, potentially underlying heat-induced cellular vulnerability in older men.NEW & NOTEWORTHY We demonstrate that autophagic stimulation occurs in response to short-duration (30-min) vigorous-intensity exercise in peripheral blood mononuclear cells from older adults; however, no changes in autophagy occur during low- or moderate-intensity exercise. Moreover, older adults exhibit autophagic impairments when the same vigorous-intensity exercise is performed in hot ambient conditions. When paired with an attenuated heat shock response, as well as elevated apoptotic responses, older men may exhibit greater cellular vulnerability to exertional heat stress.

Capsaicin binds the N-terminus of Hsp90, induces lysosomal degradation of Hsp70, and enhances the anti-tumor effects of 17-AAG (Tanespimycin)

Heat shock protein 90 (Hsp90) and its co-chaperones promote cancer, and targeting Hsp90 holds promise for cancer treatment. Most of the efforts to harness this potential have focused on targeting the Hsp90 N-terminus ATP binding site. Although newer-generation inhibitors have shown improved efficacy in aggressive cancers, induction of the cellular heat shock response (HSR) by these inhibitors is thought to limit their clinical efficacy. Therefore, Hsp90 inhibitors with novel mechanisms of action and that do not trigger the HSR would be advantageous. Here, we investigated the mechanism by which capsaicin inhibits Hsp90. Through mutagenesis, chemical modifications, and proteomic studies, we show that capsaicin binds to the N-terminus of Hsp90 and inhibits its ATPase activity. Consequently, capsaicin and its analogs inhibit Hsp90 ATPase-dependent progesterone receptor reconstitution in vitro. Capsaicin did not induce the HSR, instead, it promoted the degradation of Hsp70 through the lysosome-autophagy pathway. Remarkably, capsaicin did not induce degradation of the constitutively expressed cognate Hsc70, indicating selectivity for Hsp70. Combined treatments of capsaicin and the Hsp90 inhibitor 17-AAG improved the anti-tumor efficacy of 17-AAG in cell culture and tridimensional tumor spheroid growth assays using breast and prostate cancer models. Consistent with this, in silico docking studies revealed that capsaicin binding to the ATP binding site of Hsp90 was distinct from classical N-terminus Hsp90 inhibitors, indicating a novel mechanism of action. Collectively, these findings support the use of capsaicin as a chemical scaffold to develop novel Hsp90 N-terminus inhibitors as well as its ability to be a potential cancer co-therapeutic.

Proteotoxic stress-induced autophagy is regulated by the NRF2 pathway via extracellular vesicles

Protein homeostasis involves a number of overlapping mechanisms, including the autophagy program, that can lead to the resolution of protein damage. We aimed in this study to examine mechanisms of autophagy in the proteotoxic stress response. We found that such stress results in a rapid elevation in the rate of autophagy in mammalian cells. Induction of this process occurred coincidentally with the increased release of extracellular vesicles (EVs) into the extracellular microenvironment. We next found that purified EVs that had been released from stressed cells were capable of directly increasing autophagic flux in recipient cells. The EVs contained a range of cargo proteins, including HSP70, BAG3, and activated transcription factor phospho-NRF2 (pNRF2). NRF2 regulates the activation of both the oxidative stress response and autophagy genes. Both heat shock and exposure of cells to proteotoxic stress-induced EVs increased the intracellular levels of pNRF2 in cells. Heat shock-induced proteotoxicity also led to increases in the levels of proteins in the oxidative stress response, including HO-1 and NQO1, as well as the key autophagy proteins LC3, ATG5, and ATG7, known to be regulated by NRF2. Increases in these autophagy proteins were dependent on the expression of NRF2 and were ablated by NRF2 knockdown.

The Role of Heat Shock Proteins in the Pathogenesis of Polycystic Ovarian Syndrome: A Review of the Literature

Polycystic ovarian syndrome (PCOS) is the most common endocrine disorder in women of reproductive age and post-menopausal women. PCOS is a multifactorial heterogeneous disorder associated with a variety of etiologies, outcomes, and clinical manifestations. However, the pathophysiology of PCOS is still unclear. Heat shock proteins (HSPs) have recently been investigated for their role in the pathogenesis of PCOS. HSPs are a class of proteins that act as molecular chaperones and maintain cellular proteostasis. More recently, their actions beyond that of molecular chaperones have highlighted their pathogenic role in several diseases. In PCOS, different HSP family members show abnormal expression that affects the proliferation and apoptotic rates of ovarian cells as well as immunological processes. HSP dysregulation in the ovaries of PCOS subjects leads to a proliferation/apoptosis imbalance that mechanistically impacts follicle stage development, resulting in polycystic ovaries. Moreover, HSPs may play a role in the pathogenesis of PCOS-associated conditions. Recent studies on HSP activity during therapeutic interventions for PCOS suggest that modulating HSP activity may lead to novel treatment strategies. In this review, we summarize what is currently known regarding the role of HSPs in the pathogenesis of PCOS and their potential role in the treatment of PCOS, and we outline areas for future research.

Molecular mechanisms underlying the beneficial effects of exercise and dietary interventions in the prevention of cardiometabolic diseases

Cardiometabolic diseases still represent a major cause of mortality worldwide. In addition to pharmacological approaches, lifestyle interventions can also be adopted for the prevention of these morbid conditions. Lifestyle changes include exercise and dietary restriction protocols, such as calorie restriction and intermittent fasting, which were shown to delay cardiovascular ageing and elicit health-promoting effects in preclinical models of cardiometabolic diseases. Beneficial effects are mediated by the restoration of multiple molecular mechanisms in heart and vessels that are compromised by metabolic stress. Exercise and dietary restriction rescue mitochondrial dysfunction, oxidative stress and inflammation. They also improve autophagy. The result of these effects is a marked improvement of vascular and heart function. In this review, we provide a comprehensive overview of the molecular mechanisms involved in the beneficial effects of exercise and dietary restriction in models of diabetes and obesity. We also discuss clinical studies and gap in animal-to-human translation.

Celastrol inhibits rheumatoid arthritis by inducing autophagy via inhibition of the PI3K/AKT/mTOR signaling pathway

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disorder of the synovial joints. Celastrol (Cel) is a quinone-methylated triterpenoid extracted from Tripterygium wilfordii Hook F (TwHF) that has been proven to be effective in treating RA. However, the underlying molecular mechanism of celastrol in the treatment of RA remains unknown. This study explored the protective effect of celastrol against RA and the specific mechanisms of celastrol in vitro and in vivo.

METHODS

A chicken type II collagen (CII)-induced arthritis (CIA) mouse model was used to explore the anti-arthritic effects of celastrol, and paw swelling degree, the poly-arthritis index score and serum cytokine levels were determined. Pathological morphology was observed using hematoxylin and eosin (H&E) staining. The influences of celastrol on the proliferation of tumor necrosis factor-α (TNF-α)-induced fibroblast-like synoviocytes (FLSs) were tested by Cell Counting Kit-8 (CCK-8) assays and5-ethynyl-2'-deoxyuridine (EdU) staining assays. The level of autophagy was detected by transmission electron microscopy (TEM). Furthermore, the PI3K/AKT/mTOR pathway and the status of autophagy in the CIA model and FLSs were also detected by western blot and immunofluorescence staining.

RESULTS

The results showed that celastrol decreased arthritis severity and inhibited TNF-α-induced FLSs proliferation. Additionally, celastrol decreased the secretion of pro-inflammatory cytokines. Moreover, celastrol increased autophagosome levels and LC3B protein expression in TNF-α-treated FLSs. Furthermore, celastrol increased the protein expression of LC3-II and Beclin-1 and decreased the phosphorylation degree of mTOR and AKT.

CONCLUSION

In conclusion, our findings confirmed that celastrol ameliorates RA via the up-regulation of autophagy by inhibiting the PI3K/AKT/mTOR axis.

The autophagic response to exercise in peripheral blood mononuclear cells from young men is intensity-dependent and is altered by exposure to environmental heat

Autophagy is essential to maintaining cellular homeostasis in all eukaryotic cells and to tolerance of acute stressors such as starvation, heat, and recovery following exercise. Limited information exists regarding the exercise intensity-dependent autophagic response in humans, and it is unknown how environmental heat stress may modulate this response. Therefore, we evaluated autophagy and accompanying pathways of cellular stress (the heat shock response [HSR], apoptosis, and acute inflammation) in peripheral blood mononuclear cells (PBMCs) from 10 young men (mean [SD]; 22 [2] years) before, immediately after and up to 6h post-exercise recovery from 30 minutes of low-, moderate-, and high-intensity semi-recumbent cycling (40, 55 and 70% of maximal oxygen consumption (VO_2max), respectively)in a temperate environment (25°C) and at 70% of VO_2max in a hot environment (40°C). Changes in protein content were analyzed via Western blot. Each increase in exercise intensity was associated with elevations in mean body temperature. LC3-II increased following moderate-intensity exercise, with further increases following high-intensity exercise (p < 0.05). However, an increase in beclin-2 and ULK1, with a decrease in p62 was only observed after high-intensity exercise, which was paralleled by elevated TNF-α and cleaved-caspase-3, with the HSR peaking at 6h after exercise (p < 0.05). When exercise was performed in the heat, greater LC3-II and cleaved-caspase-3 accumulation was observed, however beclin-2 declined in recovery (p < 0.05). Therefore, our findings indicate that autophagy in PBMCs during exercise may be associated with greater heat strain exhibited during increasing exercise intensities, which is modulated by exposure to heat.

HIF1, HSF1, and NRF2: Oxidant-Responsive Trio Raising Cellular Defenses and Engaging Immune System

Cellular homeostasis is continuously challenged by damage from reactive oxygen species (ROS) and numerous reactive electrophiles. Human cells contain various protective systems that are upregulated in response to protein damage by electrophilic or oxidative stress. In addition to the NRF2-mediated antioxidant response, ROS and reactive electrophiles also activate HSF1 and HIF1 that control heat shock response and hypoxia response, respectively. Here, we review chemical and biological mechanisms of activation of these three transcription factors by ROS/reactive toxicants and the roles of their gene expression programs in antioxidant protection. We also discuss how NRF2, HSF1, and HIF1 responses establish multilayered cellular defenses consisting of largely nonoverlapping programs, which mitigates limitations of each response. Some innate immunity links in these stress responses help eliminate damaged cells, whereas others suppress deleterious inflammation in normal tissues but inhibit immunosurveillance of cancer cells in tumors.

Effects of pH alterations on stress- and aging-induced protein phase separation

Upon stress challenges, proteins/RNAs undergo liquid–liquid phase separation (LLPS) to fine-tune cell physiology and metabolism to help cells adapt to adverse environments. The formation of LLPS has been recently linked with intracellular pH, and maintaining proper intracellular pH homeostasis is known to be essential for the survival of organisms. However, organisms are constantly exposed to diverse stresses, which are accompanied by alterations in the intracellular pH. Aging processes and human diseases are also intimately linked with intracellular pH alterations. In this review, we summarize stress-, aging-, and cancer-associated pH changes together with the mechanisms by which cells regulate cytosolic pH homeostasis. How critical cell components undergo LLPS in response to pH alterations is also discussed, along with the functional roles of intracellular pH fluctuation in the regulation of LLPS. Further studies investigating the interplay of pH with other stressors in LLPS regulation and identifying protein responses to different pH levels will provide an in-depth understanding of the mechanisms underlying pH-driven LLPS in cell adaptation. Moreover, deciphering aging and disease-associated pH changes that influence LLPS condensate formation could lead to a deeper understanding of the functional roles of biomolecular condensates in aging and aging-related diseases.

Hormetic Heat Shock Enhances Autophagy through HSF1 in Retinal Pigment Epithelium Cells

To maintain homeostasis, cells have evolved stress-response pathways to cope with exogenous and endogenous stress factors. Diverse stresses at high doses may be detrimental, albeit low doses of stress, known as hormesis, can be beneficial. Upon exposure to stress, such as temperature rise, the conventional heat shock response (HSR) regulated by the heat shock transcription factor 1 (HSF1) facilitates refolding of misfolded proteins with the help of heat shock proteins (HSPs). However, the role and molecular mechanisms underlying the beneficial effects of HSR with other clearance processes, such as autophagy, remain poorly understood. In this study, human ARPE-19 cells, an in vitro model of retinal pigment epithelium, were treated with hormetic heat shock (HHS) and the autophagy expression profile was examined using quantitative PCR (qPCR), immunoblotting, immunoprecipitation, and immunofluorescence. We demonstrate that HHS enhances the expression of fundamental autophagy-associated genes in ARPE-19 cells through the activation of HSF1. HHS transiently increases the level of SQSTM1 and LC3B-II and activates autophagy. These findings reveal a role for autophagic HSF1-regulated functions and demonstrate the contribution of autophagy to hormesis in the HSR by improving proteostasis.

Heat shock protein A4 ablation leads to skeletal muscle myopathy associated with dysregulated autophagy and induced apoptosis

BACKGROUND

Molecular chaperones assist protein folding, facilitate degradation of misfolded polypeptides, and thereby maintain protein homeostasis. Impaired chaperone activity leads to defective protein quality control that is implicated in multiple skeletal muscle diseases. The heat shock protein A4 (HSPA4) acts as a co-chaperone for HSP70. Previously, we showed that Hspa4 deletion causes impaired protein homeostasis in the heart. However, its functional role in skeletal muscle has not been explored.

METHODS

We performed a comparative phenotypic and biochemical analyses of Hspa4 knockout (KO) mice with wild-type (WT) littermates.

RESULTS

HSPA4 is markedly upregulated in regenerating WT muscle in vivo, and in differentiated myoblasts in vitro. Hspa4-KO mice are marked by growth retardation and increased variability in body weight, accompanied by 35% mortality rates during the peri-weaning period. The surviving Hspa4-KO mice experienced progressive skeletal muscle myopathy, characterized by increased number of muscle fibers with centralized nuclei, heterogeneous myofiber size distribution, inflammatory cell infiltrates and upregulation of embryonic and perinatal myosin heavy chain transcripts. Hspa4-KO muscles demonstrated an accumulation of autophagosome-associated proteins including microtubule associated protein1 light chain 3-II (LC3-II) and p62/sequestosome accompanied by increased number of TUNEL-positive nuclei.

CONCLUSIONS

Our findings underscore the indispensable role of HSPA4 in maintenance of muscle integrity through contribution in skeletal muscle autophagy and apoptosis, which might provide a novel therapeutic strategy for skeletal muscle morbidities.

Hijacking Cellular Stress Responses to Promote Lifespan

Organisms are constantly exposed to stress both from the external environment and internally within the cell. To maintain cellular homeostasis under different environmental and physiological conditions, cell have adapted various stress response signaling pathways, such as the heat shock response (HSR), unfolded protein responses of the mitochondria (UPR^MT), and the unfolded protein response of the endoplasmic reticulum (UPR^ER). As cells grow older, all cellular stress responses have been shown to deteriorate, which is a major cause for the physiological consequences of aging and the development of numerous age-associated diseases. In contrast, elevated stress responses are often associated with lifespan extension and amelioration of degenerative diseases in different model organisms, including C. elegans. Activating cellular stress response pathways could be considered as an effective intervention to alleviate the burden of aging by restoring function of essential damage-clearing machinery, including the ubiquitin-proteosome system, chaperones, and autophagy. Here, we provide an overview of newly emerging concepts of these stress response pathways in healthy aging and longevity with a focus on the model organism, C. elegans.

Heat Shock Proteins and HSF1 in Cancer

Fitness of cells is dependent on protein homeostasis which is maintained by cooperative activities of protein chaperones and proteolytic machinery. Upon encountering protein-damaging conditions, cells activate the heat-shock response (HSR) which involves HSF1-mediated transcriptional upregulation of a group of chaperones - the heat shock proteins (HSPs). Cancer cells experience high levels of proteotoxic stress due to the production of mutated proteins, aneuploidy-induced excess of components of multiprotein complexes, increased translation rates, and dysregulated metabolism. To cope with this chronic state of proteotoxic stress, cancers almost invariably upregulate major components of HSR, including HSF1 and individual HSPs. Some oncogenic programs show dependence or coupling with a particular HSR factor (such as frequent coamplification of HSF1 and MYC genes). Elevated levels of HSPs and HSF1 are typically associated with drug resistance and poor clinical outcomes in various malignancies. The non-oncogene dependence ("addiction") on protein quality controls represents a pancancer target in treating human malignancies, offering a potential to enhance efficacy of standard and targeted chemotherapy and immune checkpoint inhibitors. In cancers with specific dependencies, HSR components can serve as alternative targets to poorly druggable oncogenic drivers.

Alterations of the 70 kDa heat shock protein (HSP70) and sequestosome-1 (p62) in women with breast cancer

Peripheral blood mononuclear cells (PBMCs) respond to altered physiological conditions to alleviate the threat. Production of the 70 kDa heat shock protein (HSP70) is up-regulated to protect proteins from degradation. Sequestosome-1 (p62) binds to altered proteins and the p62-protein complex is degraded by autophagy. P62 is also a regulator of intracellular kinase activity and cell differentiation. We hypothesized that the PBMC response to a malignant breast mass involves elevated production of HSP70 and a decrease in intracellular p62. In this study 46 women had their breast mass excised. PBMCs were isolated and intracellular levels of HSP70 and p62 were quantitated by ELISA. Differences between women with a benign or malignant breast mass were determined. A breast malignancy was diagnosed in 38 women (82.6%) while 8 had a benign lesion. Mean intracellular HSP70 levels were 79.3 ng/ml in PBMCs from women with a malignant lesion as opposed to 44.2 ng/ml in controls (p = 0.04). The mean PBMC p62 level was 2.3 ng/ml in women with a benign breast lesion as opposed to 0.6 ng/ml in those with breast cancer (p < 0.001). Mean p62 levels were lowest in women with invasive carcinoma and a positive lymph node biopsy when compared to those with in-situ carcinoma or absence of lymphadenopathy, respectively. Intracellular HSP70 and p62 levels in PBMCs differ between women with a malignant or benign breast lesion. These measurements may be of value in the preoperative triage of women with a breast mass.

What's Genetic Variation Got to Do with It? Starvation-Induced Self-Fertilization Enhances Survival in Paramecium

The pervasiveness of sex despite its well-known costs is a long-standing puzzle in evolutionary biology. Current explanations for the success of sex in nature largely rely on the adaptive significance of the new or rare genotypes that sex may generate. Less explored is the possibility that sex-underlying molecular mechanisms can enhance fitness and convey benefits to the individuals that bear the immediate costs of sex. Here, we show that the molecular environment associated with self-fertilization can increase stress resistance in the ciliate Paramecium tetraurelia. This advantage is independent of new genetic variation, coupled with a reduced nutritional input, and offers fresh insights into the mechanistic origin of sex. In addition to providing evidence that the molecular underpinnings of sexual reproduction and the stress response are linked in P. tetraurelia, these findings supply an integrative explanation for the persistence of self-fertilization in this ciliate.

Investigating the role of the transcriptional regulator Ure2 on the metabolism of Saccharomyces cerevisiae: a multi-omics approach

Ure2 regulates nitrogen catabolite repression in Saccharomyces cerevisiae. Deletion of URE2 induces a physiological state mimicking the nitrogen starvation and autophagic responses. Previous work has shown that deletion of URE2 increases the fermentation rate of some wine-producing strains of S. cerevisiae. In this work, we investigated the effect of URE2 deletion (ΔURE2) on the metabolism of S. cerevisiae. During growth on glucose, the ΔURE2 mutant grew at a 40% slower rate than the wild type; however, it produced ethanol at a 31% higher rate. To better under the behavior of this mutant, we performed transcriptomics and metabolomics. Analysis of the RNA sequencing results and metabolite levels indicates that the mutant strain exhibited characteristics of both nitrogen starvation and autophagy, including the upregulation of allantoin, urea, and amino acid uptake and utilization pathways and selective autophagic machinery. In addition, pyruvate decarboxylase and alcohol dehydrogenase isoforms were expressed at higher rates than the wild type. The mutant also accumulated less trehalose and glycogen, and produced more lipids. The induction of a nitrogen starvation-like state and increase in lipid production in nitrogen-rich conditions suggest that URE2 may be a promising target for metabolic engineering in S. cerevisiae and other yeasts for the production of lipids and lipid-derived compounds. KEY POINTS: • Deletion of URE2 increases ethanol and lipid production in Saccharomyces cerevisiae. • Deletion of URE2 reduces glycogen and trehalose production. • Metabolic changes mimic nitrogen starvation and autophagic response.

Maternal obesity interrupts the coordination of the unfolded protein response and heat shock response in the postnatal developing hypothalamus of male offspring in mice

Maternal obesity malprograms offspring obesity and associated metabolic disorder. As a common phenomenon in obesity, endoplasmic reticulum (ER) stress also presents early prior to the development. Here, we investigate metabolic effect of early activated hypothalamic ER stress in offspring exposed to maternal obesogenic environment and the underlying mechanism in ICR mice model. We found higher body weight, hyperphagia and defective hypothalamic feeding-circuit in the offspring born to obese dams, with hypothalamic ER stress, and even more comprehensive cell proteotoxic stress were induced during the early postnatal period. However, neonatal inhibition of hypothalamic ER stress worsened the metabolic end. We believe that the uncoordinated interaction between the unfolded protein response and the heat shock response, regulated by heat shock protein 70, might be responsible for the malformed hypothalamic feeding circuit of the offspring exposure to maternal obesogenic conditions and were linked with deleterious metabolism in adulthood, especially when exposure to high-energy conditions.

Autophagy facilitates mitochondrial rebuilding after acute heat stress via a DRP-1-dependent process

Acute heat stress (aHS) can induce strong developmental defects in Caenorhabditis elegans larva but not lethality or sterility. This stress results in transitory fragmentation of mitochondria, formation of aggregates in the matrix, and decrease of mitochondrial respiration. Moreover, active autophagic flux associated with mitophagy events enables the rebuilding of the mitochondrial network and developmental recovery, showing that the autophagic response is protective. This adaptation to aHS does not require Pink1/Parkin or the mitophagy receptors DCT-1/NIX and FUNDC1. We also find that mitochondria are a major site for autophagosome biogenesis in the epidermis in both standard and heat stress conditions. In addition, we report that the depletion of the dynamin-related protein 1 (DRP-1) affects autophagic processes and the adaptation to aHS. In drp-1 animals, the abnormal mitochondria tend to modify their shape upon aHS but are unable to achieve fragmentation. Autophagy is induced, but autophagosomes are abnormally elongated and clustered on mitochondria. Our data support a role for DRP-1 in coordinating mitochondrial fission and autophagosome biogenesis in stress conditions.

Autophagy and heat: a potential role for heat therapy to improve autophagic function in health and disease

Autophagy is a crucial cell survival mechanism that involves the degradation and recycling of old or damaged organelles and proteins to maintain cellular homeostasis. Impairments in autophagy are central to the pathogenesis of many conditions including metabolic and neurodegenerative disorders, cardiovascular and pulmonary diseases, diabetes, and aging. Although various pharmacological agents may be able to stimulate autophagic function, to our knowledge, few interventions exist that have been deemed safe and effective in humans. An emerging body of evidence suggests that targeting the autophagic pathway via passive heating (heat therapy) may stimulate autophagic function. Therefore, the primary focus of the present review is to analyze the mechanisms in which passive heating induces autophagy as defined by in vitro and in vivo (animal and human) models. Our secondary focus is to examine the implications of utilizing passive heating to restore dysfunctional autophagy in chronic disease and aging. Finally, we discuss potential therapeutic strategies to implement passive heating to stimulate autophagic function in humans.

Melanogenesis Connection with Innate Immunity and Toll-Like Receptors

The epidermis is located in the outermost layer of the living body and is the place where external stimuli such as ultraviolet rays and microorganisms first come into contact. Melanocytes and melanin play a wide range of roles such as adsorption of metals, thermoregulation, and protection from foreign enemies by camouflage. Pigmentary disorders are observed in diseases associated with immunodeficiency such as Griscelli syndrome, indicating molecular sharing between immune systems and the machineries of pigment formation. Melanocytes express functional toll-like receptors (TLRs), and innate immune stimulation via TLRs affects melanin synthesis and melanosome transport to modulate skin pigmentation. TLR2 enhances melanogenetic gene expression to augment melanogenesis. In contrast, TLR3 increases melanosome transport to transfer to keratinocytes through Rab27A, the responsible molecule of Griscelli syndrome. TLR4 and TLR9 enhance tyrosinase expression and melanogenesis through p38 MAPK (mitogen-activated protein kinase) and NFκB signaling pathway, respectively. TLR7 suppresses microphthalmia-associated transcription factor (MITF), and MITF reduction leads to melanocyte apoptosis. Accumulating knowledge of the TLRs function of melanocytes has enlightened the link between melanogenesis and innate immune system.

Functional inhibition of heat shock protein 70 by VER-155008 suppresses pleural mesothelioma cell proliferation via an autophagy mechanism

Background: Pleural mesothelioma, a devastating asbestos‐associated malignancy, urgently requires a novel effective therapy. Heat shock protein 70 (HSP70), which is synthesized in the cell response to protein damage, is expected to be a new target for antitumor treatment. In addition to its well‐known protein refolding function, HSP70 regulates cell proliferation through different pathways, including PI3K/AKT/mTOR, and autophagy in malignant cells. In this study, we attempted to clarify the effects of VER‐155008, an HSP70 inhibitor, on pleural mesothelioma.

Methods: Human pleural mesothelioma cell lines 211H, H2452 and H28 were cultured with VER‐155008, and protein expression, cell proliferation, colony formation, cell cycle, synergistic effect with cisplatin, and autophagy induction were analyzed.

Results: In mesothelioma cell lines, VER‐155008 (5.0 μM or more) inhibited cell growth and colony formation, accompanied by G₁ cell cycle arrest. According to western blot analysis, VER‐155008 reduced p‐AKT expression. However, VER‐155008 failed to show a synergistic effect with cisplatin on cell growth. Mesothelioma cells transfected with the novel plasmid pMRX‐IP‐GFP‐LC3‐RFP‐LC3ΔG, which was developed for the quantitative and statistical estimation of macroautophagy, showed enhanced macroautophagy upon treatment with VER‐155008 and gefitinib which is an EGFR‐tyrosine kinase inhibitor. In addition, fetal bovine serum deprivation induced macroautophagy was further enhanced by VER‐155008.

Conclusions: On the basis of these results, functional HSP70 inhibition by VER‐155008 suppressed cell growth in pleural mesothelioma cells, accompanied by enhanced macroautophagy. HSP70 inhibition is thus expected to become a new strategy for treating mesothelioma.

Key points

Significant findings of the study

In pleural mesothelioma cells, inhibition of HSP70 function by VER‐155008 suppressed cell proliferation accompanied by induction of autophagy which was synergistically enhanced under the starvation condition, whereas gefitinib, an EGFR‐TKI, did not show the same synergistic effect in autophagy.

What this study adds

The inhibition of HSP70 induced autophagy and suppressed cell proliferation in mesothelioma cells.

Heat shock increases levels of reactive oxygen species, autophagy and apoptosis

Hyperthermia is a promising anticancer treatment used in combination with radiotherapy and chemotherapy. Temperatures above 41.5 °C are cytotoxic and hyperthermia treatments can target a localized area of the body that has been invaded by a tumor. However, non-lethal temperatures (39-41 °C) can increase cellular defenses, such as heat shock proteins. This adaptive survival response, thermotolerance, can protect cells against subsequent cytotoxic stress such as anticancer treatments and heat shock (>41.5 °C). Autophagy is another survival process that is activated by stress. This study aims to determine whether autophagy can be activated by heat shock at 42 °C, and if this response is mediated by reactive oxygen species (ROS). Autophagy was increased during shorter heating times (<60 min) at 42 °C in cells. Levels of acidic vesicular organelles (AVO) and autophagy proteins Beclin-1, LC3-II/LC-3I, Atg7 and Atg12-Atg5 were increased. Heat shock at 42 °C increased levels of ROS. Increased levels of LC3 and AVOs at 42 °C were inhibited by antioxidants. Therefore, increased autophagy during heat shock at 42 °C (<60 min) was mediated by ROS. Conversely, heat shock at 42 °C for longer times (1-3 h) caused apoptosis and activation of caspases in the mitochondrial, death receptor and endoplasmic reticulum (ER) pathways. Thermotolerant cells, which were developed at 40 °C, were resistant to activation of apoptosis at 42 °C. Autophagy inhibitors 3-methyladenine and bafilomycin sensitized cells to activation of apoptosis by heat shock (42 °C). Improved understanding of autophagy in cellular responses to heat shock could be useful for optimizing the efficacy of hyperthermia in the clinic.

Oridonin suppresses autophagy and survival in rheumatoid arthritis fibroblast-like synoviocytes

Context: Oridonin exhibits various pharmacological and physiological activities, including antioxidant, antibacterial, anti-inflammatory, pro-apoptotic, anticancer and neurological effects. However, its role in rheumatoid arthritis (RA) is yet to be revealed.Objective: We evaluated the effects of oridonin on the survival and autophagy of RA-fibroblast-like synoviocytes (FLSs).Materials and methods: RA-FLSs were treated with oridonin at serial concentrations of 0, 2, 4, 6, 8 and 10 µg/mL for 24, 48 and 72 h. Then, cell proliferation and apoptosis were measured. A GFP-LC3 plasmid was transfected into the cells to determine autophagy.Results: Oridonin suppressed RA-FLS proliferation in a dose-dependent manner. The half maximal inhibitory concentrations (IC₅₀) of oridonin at 24, 48 and 72 h were 8.28, 7.88 and 8.35 µg/mL, respectively. Treatment with oridonin for 24 h increased apoptosis by 4.1%, and increased the protein levels of Bax and cleaved caspase-3 but significantly decreased the levels of IL-1β in the culture supernatant (p < 0.05). In addition, 6 h of oridonin treatment significantly decreased the number of GFP-LC3 punctate dots and inhibited the protein levels of ATG5 and Beclin1 by 80.01% and 42.12%, respectively. Chloroquine (CQ) significantly reinforced the effects of oridonin on inhibition of autophagy, suppression of proliferation, and induction of apoptosis in RA-FLSs (p < 0.05).Conclusions: Our results indicate that treatment with oridonin in combination with CQ inhibits autophagy and cell proliferation and induces apoptosis in RA-FLSs more effectively than treatment oridonin alone. This finding indicates that oridonin is a potential therapeutic agent for RA.

Impaired autophagy following ex vivo heating at physiologically relevant temperatures in peripheral blood mononuclear cells from elderly adults

With the increasing threat of climate change and the accompanying rise in the frequency and severity of extreme heat events, there are growing health concerns for heat-vulnerable elderly adults. Elderly adults are at increased risk of developing heat-related injuries, in part due to age-related declines in thermoregulatory and cellular function. Regarding the latter, the process of autophagy is activated as a cellular protective mechanism to counter heat-induced stress, but the extent that heat stress activates autophagy in elderly adults is not known. Further, the interplay between autophagy, the heat shock response (HSR), the acute inflammatory response, and apoptosis remains poorly understood in elderly adults. Therefore, the purpose of this study was to examine changes in autophagy, the HSR, inflammation, and apoptosis following increasing levels of ex vivo heat stress representative of physiologically relevant increases in body core temperatures (37-41 °C). Whole blood from 20 elderly adults (72 ± 4 years; 14 men, 6 women) was heated (via water immersion) to temperatures representative of normal resting conditions (normothermia; 37 °C), in addition to moderate and severe heat stress conditions (39, and 41 °C, respectively) for 90 min. Peripheral blood mononuclear cells (PBMC) were isolated and protein markers of autophagy, the HSR, acute inflammation, and apoptosis were examined. No significant increases in markers of autophagy or the HSR were observed following any temperature condition. However, an increase in acute inflammation was observed above baseline following moderate heat stress (39 °C), with further increases in inflammation and apoptosis observed during severe heat stress (41 °C). Our findings indicate that PBMCs from elderly adults do not exhibit increases in autophagy or the HSR following severe heat stress, potentially contributing to the elevated risk of cellular dysfunction seen in elderly adults during heat stress.

Hsp70 in cancer: A double agent in the battle between survival and death

The heat shock protein (Hsps) superfamily, also known as molecular chaperones, are highly conserved and present in all living organisms and play vital roles in protein fate. The HspA1A (Hsp70-1), called Hsp70 in this review, is expressed at low or undetectable levels in most unstressed normal cells, but numerous studies have shown that diverse types of tumor cells express Hsp70 at the plasma membrane that leads to resistance to programmed cell death and tumor progression. Hsp70 is released into the extracellular milieu in three forms including free soluble, complexed with cancer antigenic peptides, and exosome forms. Therefore, it seems to be a promising therapeutic target in human malignancies. However, a great number of studies have indicated that both intracellular and extracellular Hsp70 have a dual function. A line of evidence presented that intracellular Hsp70 has a cytoprotective function via suppression of apoptosis and lysosomal cell death (LCD) as well as that extracellular Hsp70 can promote tumorigenesis and angiogenesis. Other evidence showed intracellular Hsp70 can promote apoptosis and membrane-associated/extracellular Hsp70 can elicit antitumor innate and adaptive immune responses. Given the contradictory functions, as a "double agent," could Hsp70 be a promising tool in the future of targeted cancer therapies? To answer this question, in this review, we will discuss the functions of Hsp70 in cancers besides inhibition and stimulation strategies for targeting Hsp70 along with their challenges.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.

Autophagy is a pro-survival adaptive response to heat shock in bovine cumulus-oocyte complexes

Autophagy is a physiological mechanism that can be activated under stress conditions. However, the role of autophagy during oocyte maturation has been poorly investigated. Therefore, this study characterized the role of autophagy on developmental competence and gene expression of bovine oocytes exposed to heat shock (HS). Cumulus-oocyte-complexes (COCs) were matured at Control (38.5 °C) and HS (41 °C) temperatures in the presence of 0 and 10 mM 3-methyladenine (3MA; autophagy inhibitor). Western blotting analysis revealed that HS increased autophagy marker LC3-II/LC3-I ratio in oocytes. However, there was no effect of temperature for oocytes matured with 3MA. On cumulus cells, 3MA reduced LC3-II/LC3-I ratio regardless of temperature. Inhibition of autophagy during IVM of heat-shocked oocytes (3MA-41 °C) reduced cleavage and blastocyst rates compared to standard in vitro matured heat-shocked oocytes (IVM-41 °C). Therefore, the magnitude of HS detrimental effects was greater in the presence of autophagy inhibitor. Oocyte maturation under 3MA-41 °C reduced mRNA abundance for genes related to energy metabolism (MTIF3), heat shock response (HSF1), and oocyte maturation (HAS2 and GREM1). In conclusion, autophagy is a stress response induced on heat shocked oocytes. Inhibition of autophagy modulated key functional processes rendering the oocyte more susceptible to the deleterious effects of heat shock.

Treatment with Melittin Induces Apoptosis and Autophagy of Fibroblast-like Synoviocytes in Patients with Rheumatoid Arthritis

Background:

Melittin, the major medicinal component of honeybee venom, exerts antiinflammatory, analgesic, and anti-arthritic effects in patients with Rheumatoid Arthritis (RA). RA is an inflammatory autoimmune joint disease that leads to irreversible joint destruction and functional loss. Fibroblast-Like Synoviocytes (FLS) are dominant, special mesenchymal cells characterized by the structure of the synovial intima, playing a crucial role in both the initiation and progression of RA.

Objective:

In this study, we evaluated the effects of melittin on the viability and apoptosis of FLS isolated from patients with RA.

Methods:

Cell viability was determined using CCK-8 assays; apoptosis was evaluated by flow cytometry, and the expression levels of apoptosis-related proteins (caspase-3, caspase-9, BAX, and Bcl-2) were also determined. To explore whether melittin alters inflammatory processes in RA-FLS, IL-1β levels were determined using an enzyme-linked immunosorbent assay (ELISA). Furthermore, we performed GFP-LC3 punctate fluorescence dot assays and western blotting (for LC3, ATG5, p62, and Beclin 1) to assess autophagy in RA-FLS.

Results:

Our results show that melittin can significantly impair viability, promote apoptosis and autophagy, and inhibit IL-1β secretion in RA-FLS.

Conclusion:

Melittin may be useful in preventing damage to the joints during accidental local stimulation.

Autophagy protects HUVECs against ER stress-mediated apoptosis under simulated microgravity

Astronauts exposed to a gravity-free environment experience cardiovascular deconditioning that causes post-spaceflight orthostatic intolerance and other pathological conditions. Endothelial dysfunction is an important factor responsible for this alteration. Our previous study showed enhanced autophagy in endothelial cells under simulated microgravity. The present study explored the cytoprotective role of autophagy under microgravity in human umbilical vein endothelial cells (HUVECs). We found that clinorotation for 48 h induced apoptosis and endoplasmic reticulum (ER) stress in HUVECs. ER stress and the unfolded protein response (UPR) partially contributed to apoptosis under clinorotation. Autophagy partially reduced ER stress and restored UPR signaling by autophagic clearance of ubiquitin-protein aggregates, thereby reducing apoptosis. In addition, the ER stress antagonist 4-phenylbutyric acid upregulated autophagy in HUVECs. Taken together, these findings indicate that autophagy plays a protective role against apoptosis under clinorotation by clearing protein aggregates and partially restoring the UPR.

Targeting metabolic syndrome with phytochemicals: Focus on the role of molecular chaperones and hormesis in drug discovery

Adaptive cellular stress response confers stress tolerance against inflammatory and metabolic disorders. In response to metabolic stress, the key mediator of cellular adaptation and tolerance is a class of molecules called the molecular chaperones (MCs). MCs are highly conserved molecules that play critical role in maintaining protein stability and functionality. Hormesis in this context is a unique adaptation mechanism where a low dose of a stressor (which is toxic at high dose) confers a stress-resistant adaptive cellular phenotype. Hormesis can be observed at different level of biological organization at various measurable endpoints. The MCs are believed to play a key role in adaptation during hormesis. Several phytochemicals are known for their hormetic response and are called phytochemical hormetins. The role of phytochemical-mediated hormesis on the adaptive cellular processes is proposed as a potential therapeutic approach to target inflammation associated with metabolic syndrome. However, the screening of phytochemical hormetins would require a paradigm shift in the methods currently used in drug discovery.

Hyperthermia and protein homeostasis: Cytoprotection and cell death

Protein homeostasis or proteostasis, the correct balance between production and degradation of proteins, is an essential pillar for proper cellular function. Among the several cellular mechanisms that disrupt homeostatic conditions in cancer cells, hyperthermia (HT) has shown promising anti-tumor effects. However, cancer cells are also capable of thermoresistance. Indeed, HT-induced protein denaturation and aggregation results in the up regulation of heat shock proteins, a group of molecular chaperones with cytoprotective and anti-apoptotic properties via stress-inducible transcription factor, heat shock factor 1(HSF1). Heat shock proteins assist in the refolding of misfolded proteins and aids in their elimination if they become irreversibly damaged by various stressors. Furthermore, HSF1 also initiates the unfolded protein response in the endoplasmic reticulum (ER) to assist in the protein folding capacity of ER and also promotes the translation of pro-survival proteins' mRNA such as activating transcription factor 4 (ATF 4). Moreover, HT associated induction of microRNAs is also involved in thermal resistance of cancer cells via up-regulation of anti-apoptotic Bcl-2 proteins and down regulation of pro-apoptotic Bax and caspase 3 activities. Another cellular protection in response to stressors is Autophagy, which is regulated by the Mammalian target of rapamycin (mTOR) protein. Kinase activity in mTOR phosphorylates HSF1 and promotes its nuclear translocation for heat shock protein synthesis. Over-expression of heat shock proteins are reported to up-regulate Beclin-1, an autophagy initiator. Moreover, HT-induced reactive oxygen species (ROS) generation is sensitized by transcription factor NF-E2 related factor 2 (Nrf2) and activates the cellular expression of antioxidants and autophagy gene. Furthermore, ROS also potentiates autophagy via activation of Beclin-1. Inhibition of thermotolerance can potentiate HT-induced apoptosis. Here, we outlined that heat stress alters cellular proteins which activates cellular homeostatic processes to promote cell survival and make cancer cells thermotolerant.

Late gestation heat stress in dairy cows: Effects on dam and daughter

In dairy cattle, the final weeks before parturition are physiologically challenging and an important determinant of subsequent production performance. External stressors should be carefully managed during this period to avoid adding strain on the animals. Late-gestation heat stress impairs productivity in the dam and exerts transgenerational effects on progeny. Physiological responses are complex and detriments to performance are multifaceted. Late-gestation heat stress blunts mammary gland involution in the first half of the dry period and impairs cell proliferation as calving approaches. Moreover, cows that were exposed to prepartum heat-stress exhibit reduced adipose tissue mobilization and a lower degree of insulin resistance during early lactation. Prepartum heat exposure also depresses immune function and evidence links this decrease to altered prolactin signaling under heat stress. Placental functions are also impaired as reflected in a higher cotyledon mass but lower maternal circulating estrone sulfate concentrations, potentially resulting in lower nutrient supply and reduced calf birth weight. In addition, calves born to heat-stressed dams show impaired immune function and therefore higher disease susceptibly. Novel evidence reported that intrauterine heat stress alters the methylation profile of liver and mammary DNA, which may also contribute to the poorer performance during adulthood of calves exposed to heat stress in utero. Understanding the contribution of all altered biological systems during late-gestation heat stress can be used as a basis for improving cow management during the dry period. This article provides a review of the impacts of late-gestation heat stress and of the emerging understanding of the biological mechanisms that underlie the observed impairments of performance.

Autophagy compensates for defects in mitochondrial dynamics

Compromising mitochondrial fusion or fission disrupts cellular homeostasis; however, the underlying mechanism(s) are not fully understood. The loss of C. elegans fzo-1MFN results in mitochondrial fragmentation, decreased mitochondrial membrane potential and the induction of the mitochondrial unfolded protein response (UPRmt). We performed a genome-wide RNAi screen for genes that when knocked-down suppress fzo-1MFN(lf)-induced UPRmt. Of the 299 genes identified, 143 encode negative regulators of autophagy, many of which have previously not been implicated in this cellular quality control mechanism. We present evidence that increased autophagic flux suppresses fzo-1MFN(lf)-induced UPRmt by increasing mitochondrial membrane potential rather than restoring mitochondrial morphology. Furthermore, we demonstrate that increased autophagic flux also suppresses UPRmt induction in response to a block in mitochondrial fission, but not in response to the loss of spg-7AFG3L2, which encodes a mitochondrial metalloprotease. Finally, we found that blocking mitochondrial fusion or fission leads to increased levels of certain types of triacylglycerols and that this is at least partially reverted by the induction of autophagy. We propose that the breakdown of these triacylglycerols through autophagy leads to elevated metabolic activity, thereby increasing mitochondrial membrane potential and restoring mitochondrial and cellular homeostasis.

Heat-shock transcription factor 2 promotes sodium butyrate-induced autophagy by inhibiting mTOR in ulcerative colitis

Butyrate-induced autophagy and anti-inflammatory effects of IECs plays an important role in UC. HSP has been proved to be associated with autophagy. HSF2, as an important regulator of HSP, has been determined to be highly expressed in UC. This study was designed to elucidate the relationship between HSF2, butyrate and epithelial autophagy and the potential mechanism of HSF2-related autophagy in UC. The autophagy levels and HSF2 expression in intestinal mucosa were increased in UC patients compared to controls. In DSS colitis models, hsf2^-/- mice exhibited more severe intestinal inflammation and lower autophagy levels than wild-type mice. HSF2 expression could be induced by sodium butyrate and LPS as a dose-response relationship in HT-29 cells, epigenetically via increasing histone acetylation levels at the promoter region by sodium butyrate. Autophagy induced by sodium butyrate was promoted by overexpression HSF2 in HT-29 cells. Moreover, overexpression HSF2 decreased the expression and phosphorylation levels of PI3K, Akt and mTOR induced by sodium butyrate. HSF2 might induced by sodium butyrate and inflammation and played protective roles in UC by enhancing autophagy of IECs. This indicated that HSF2 may be a critical target for autophagy modulation and a new potential therapeutic target in UC.

Intracellular C3 Protects Human Airway Epithelial Cells from Stress-associated Cell Death

The complement system provides host defense against pathogens and environmental stress. C3, the central component of complement, is present in the blood and increases in BAL fluid after injury. We recently discovered that C3 is taken up by certain cell types and cleaved intracellularly to C3a and C3b. C3a is required for CD4⁺ T-cell survival. These observations made us question whether complement operates at environmental interfaces, particularly in the respiratory tract. We found that airway epithelial cells (AECs, represented by both primary human tracheobronchial cells and BEAS-2B [cell line]) cultured in C3-free media were unique from other cell types in that they contained large intracellular stores of de novo synthesized C3. A fraction of this protein reduced ("storage form") but the remainder did not, consistent with it being pro-C3 ("precursor form"). These two forms of intracellular C3 were absent in CRISPR knockout-induced C3-deficient AECs and decreased with the use of C3 siRNA, indicating endogenous generation. Proinflammatory cytokine exposure increased both stored and secreted forms of C3. Furthermore, AECs took up C3 from exogenous sources, which mitigated stress-associated cell death (e.g., from oxidative stress or starvation). C3 stores were notably increased within AECs in lung tissues from individuals with different end-stage lung diseases. Thus, at-risk cells furnish C3 through biosynthesis and/or uptake to increase locally available C3 during inflammation, while intracellularly, these stores protect against certain inducers of cell death. These results establish the relevance of intracellular C3 to airway epithelial biology and suggest novel pathways for complement-mediated host protection in the airway.

Heat shock pretreatment improves mesenchymal stem cell viability by heat shock proteins and autophagy to prevent cisplatin-induced granulosa cell apoptosis

Background

Bone marrow mesenchymal stem cells (BMSCs) can partially repair chemotherapy-induced ovarian damage. However, low survival rate after transplantation hampers the therapeutic efficiency of BMSCs. Heat shock pretreatment (HSP) effectively improves the cell survival. This study attempted to investigate the mechanisms of HSP on BMSCs survival and the effects of heat shock-pretreated BMSCs (HS-MSCs) on cisplatin-induced granulosa cell (GC) apoptosis.

Methods

BMSCs were isolated, cultured, and identified. After receiving HSP for different duration times in a 42 °C water bath, the apoptotic rates of BMSCs were detected by Annexin V-FITC/PI to determine the optimal condition of HSP. Cisplatin was added to the medium of HS-MSCs to simulate chemotherapy environment. The proliferative curve, apoptotic rate, and viability of HS-MSCs were determined by CCK-8, Annexin V-FITC/PI, and Hoechst33342/PI respectively to explore the alteration of biological characteristics. The levels of heat shock protein 70 and 90 (HSP70 and HSP90) and the expressions of autophagy-related markers (Beclin1 and LC3B) were detected by Western blot. In addition, the autophagosomes were observed by transmission electronic microscopy to discuss the possible mechanisms. The GCs were isolated, cultured, and identified. The HS-MSCs were co-cultured with GCs before and after the addition of cisplatin. Then, the apoptotic rate and viability of GCs were detected to investigate the therapeutic and preventive effects of HS-MSCs on GC apoptosis.

Results

After receiving HSP at 42 °C for 1 h, BMSCs represented the lowest apoptotic rate. After the addition of cisplatin, the apoptotic rate of HS-MSCs (11.94% ± 0.63%) was lower than that of BMSCs (14.30% ± 0.80%) and the percentage of HS-MSCs expressing bright blue/dull red fluorescence was lower than that of BMSCs. The expression of HSP70 and HSP90 increased, while the number of autophagosomes, the expression of Beclin1, and the LC3BII/LC3BI ratio decreased in HS-MSCs. The apoptotic rates of GCs co-cultured with HS-MSCs before and after the addition of cisplatin were 39.88% ± 1.65% and 36.72% ± 0.96%, both lower than those of cisplatin-induced GCs (53.81% ± 1.89%).

Conclusion

HSP can alleviate the apoptosis and improve the survival of BMSCs under chemotherapy environment. The mechanism may be associated with the elevated expression of HSP70 and HSP90 and the attenuation of autophagy. Moreover, HS-MSCs have both therapeutic and preventive effects on cisplatin-induced GC apoptosis.

Conserved Autophagy Pathway Contributes to Stress Tolerance and Virulence and Differentially Controls Autophagic Flux Upon Nutrient Starvation in Cryptococcus neoformans

Autophagy is mainly a catabolic process, which is used to cope with nutrient deficiency and various stress conditions. Human environment often imposes various stresses on Cryptococcus neoformans, a major fungal pathogen of immunocompromised individuals; therefore, autophagic response of C. neoformans to these stresses often determines its survival in the host. However, a systematic study on how autophagy related (ATG) genes influence on autophagic flux, virulence, stress response and pathogenicity of C. neoformans is lacking. In this study, 22 ATG-deficient strains were constructed to investigate their roles in virulence, pathogenesis, stress response, starvation tolerance and autophagic flux in C. neoformans. Our results showed that Atg6 and Atg14-03 significantly affect the growth of C. neoformans at 37°C and laccase production. Additionally, atg2Δ and atg6Δ strains were sensitive to oxidative stress caused by hydrogen peroxide. Approximately half of the atgΔ strains displayed higher sensitivity to 1.5 M NaCl and remarkably lower virulence in the Galleria mellonella model than the wild type. Autophagic flux in C. neoformans was dependent on the Atg1-Atg13, Atg5-Atg12-Atg16, and Atg2-Atg18 complexes and Atg11. Cleavage of the green fluorescent protein (GFP) from Atg8 was difficult to detect in these autophagy defective mutants; however, it was detected in the atg3Δ, atg4Δ, atg6Δ and atg14Δ strains. Additionally, no homologs of Saccharomyces cerevisiae ATG10 were detected in C. neoformans. Our results indicate that these ATG genes contribute differentially to carbon and nitrogen starvation tolerance in C. neoformans compared with S. cerevisiae. Overall, this study advances our knowledge of the specific roles of ATG genes in C. neoformans.

HSF1Base: A Comprehensive Database of HSF1 (Heat Shock Factor 1) Target Genes

HSF1 (heat shock factor 1) is an evolutionarily conserved master transcriptional regulator of the heat shock response (HSR) in eukaryotic cells. In response to high temperatures, HSF1 upregulates genes encoding molecular chaperones, also called heat shock proteins, which assist the refolding or degradation of damaged intracellular proteins. Accumulating evidence reveals however that HSF1 participates in several other physiological and pathological processes such as differentiation, immune response, and multidrug resistance, as well as in ageing, neurodegenerative demise, and cancer. To address how HSF1 controls these processes one should systematically analyze its target genes. Here we present a novel database called HSF1Base (hsf1base.org) that contains a nearly comprehensive list of HSF1 target genes identified so far. The list was obtained by manually curating publications on individual HSF1 targets and analyzing relevant high throughput transcriptomic and chromatin immunoprecipitation data derived from the literature and the Yeastract database. To support the biological relevance of HSF1 targets identified by high throughput methods, we performed an enrichment analysis of (potential) HSF1 targets across different tissues/cell types and organisms. We found that general HSF1 functions (targets are expressed in all tissues/cell types) are mostly related to cellular proteostasis. Furthermore, HSF1 targets that are conserved across various animal taxa operate mostly in cellular stress pathways (e.g., autophagy), chromatin remodeling, ribosome biogenesis, and ageing. Together, these data highlight diverse roles for HSF1, expanding far beyond the HSR.

The Effect of Heat Stress on Autophagy and Apoptosis of Rumen, Abomasum, Duodenum, Liver and Kidney Cells in Calves

The objective of this study was to assess the effect of heat stress on the autophagy and apoptosis of the rumen, abomasum, duodenum, liver and kidney in calves. Two groups of Holstein male calves were selected with similar birth weights and health conditions. Heat stress (HT): Six calves (birth weight 42.2 ± 2.3) were raised from July 15 to August 19. Cooling (CL): Six calves (birth weight 41.5 ± 3.1 kg) were raised from April 10 to May 15. All the calves were euthanized following captive bolt gun stunning at 35 d of age. The expression of protein 1 light chain 3-Ⅱ (LC3-Ⅱ) and caspase3 in the rumen, abomasum, duodenum, liver and kidney were determined by western blotting. In addition, other possible relevant serum biochemical parameters were evaluated. Significant differences were observed in alkaline phosphatase (ALP), albumin (ALB) and glucose (Glu). The results showed that heat stress could increase the autophagy and apoptosis of the kidney, duodenum and abomasum. However, heat stress had no effect on the autophagy and apoptosis of the liver. Additionally, the expression of caspase-3 in the rumen in HT was significantly lower than that in CL. In conclusion, the effects of heat stress on autophagy and apoptosis are organ-specific. The results provide knowledge regarding autophagy and autophagy in calf heat stress management.

Contribution of Epithelial Cells to Defense Mechanisms in the Human Vagina

PURPOSE OF REVIEW

The vaginal milieu in women differs from that of other mammals, including non-human primates, in composition of secretions, the endogenous microbiota, and level of acidity. These changes apparently reflect evolutionary variations that maximized productive responses to a uniquely human vaginal environment. This review will highlight recent findings on properties of human vaginal epithelial cells that contribute to maintenance of a healthy vaginal environment.

RECENT FINDINGS

Vaginal epithelial cells are responsive to the composition of the vaginal microbiome even in women who are in apparently good health and do not exhibit any adverse physical symptoms. This is especially important during pregnancy when immune defenses are modified and an effective epithelial cell-derived anti-microbial activity is essential to prevent the migration to the uterus of bacteria potentially harmful to pregnancy progression. When Lactobacillus crispatus numerically predominates in the vagina, epithelial cell activity is low. Conversely, predominance of Lactobacillus iners, Gardnerella vaginalis, or other non-Lactobacilli evokes production and release of a large variety of compounds to minimize the potentially negative consequences of an altered microbiome. The extent of autophagy in vaginal epithelial cells, a basic process that functions to maintain intracellular homeostasis and engulf microbial invaders, is also sensitive to the external microbial environment Vaginal epithelial cells bind and release norepinephrine and upregulate their anti-microbial activity in response to external stress. Vaginal epithelial cells in women are responsive to local conditions that are unique to humans and, thereby, contribute to maintenance of a healthy milieu.