Tertiary structure and conformational dynamics of the anti-amyloidogenic chaperone DNAJB6b at atomistic resolution.

DNAJB6b is a molecular chaperone of the heat shock protein network, shown to play a crucial role in preventing aggregation of several disease-related intrinsically disordered proteins. Using homology modeling and microsecond-long all-atom molecular dynamics (MD) simulations, we show that monomeric DNAJB6b is a transiently interconverting protein cycling between three states: a closed state, an open state (both abundant), and a less abundant extended state. Interestingly, the reported regulatory autoinhibitory anchor between helix V in the G/F1 region and helices II/III of the J-domain, which obstructs the access of Hsp70 to the J-domain remains present in all three states. This possibly suggests a mechanistically intriguing regulation in which DNAJB6b only becomes exposed when loaded with substrates that require Hsp70 processing. Our MD results of DNAJB6b carrying mutations in the G/F1 region that are linked to limb-girdle muscular dystrophy type D1 (LGMDD1) show that this G/F1 region becomes highly dynamic, pointing towards a spontaneous release of the autoinhibitory helix V from helices II/III. This would increase the probability of non-functional Hsp70 interactions to DNAJB6b without substrates. Our cellular data indeed confirm that non-substrate loaded LGMDD1 mutants have aberrant interactions with Hsp70.

Comprehensive analysis of human tissues reveals unique expression and localization patterns of HSF1 and HSF2.

Heat shock factors (HSFs) are the main transcriptional regulators of the evolutionarily conserved heat shock response. Beyond cell stress, several studies have demonstrated that HSFs also contribute to a vast variety of human pathologies, ranging from metabolic diseases to cancer and neurodegeneration. Despite their evident role in mitigating cellular perturbations, the functions of HSF1 and HSF2 in physiological proteostasis have remained inconclusive. Here, we analyzed a comprehensive selection of paraffin-embedded human tissue samples with immunohistochemistry. We demonstrate that both HSF1 and HSF2 display distinct expression and subcellular localization patterns in benign tissues. HSF1 localizes to the nucleus in all epithelial cell types, whereas nuclear expression of HSF2 was limited to only a few cell types, especially the spermatogonia and the urothelial umbrella cells. We observed a consistent and robust cytoplasmic expression of HSF2 across all studied smooth muscle and endothelial cells, including the smooth muscle cells surrounding the vasculature and the high endothelial venules in lymph nodes. Outstandingly, HSF2 localized specifically at cell-cell adhesion sites in a broad selection of tissue types, such as the cardiac muscle, liver, and epididymis. To the best of our knowledge, this is the first study to systematically describe the expression and localization patterns of HSF1 and HSF2 in benign human tissues. Thus, our work expands the biological landscape of these factors and creates the foundation for the identification of specific roles of HSF1 and HSF2 in normal physiological processes.

Roles of heat shock protein A12A in the development of diabetic cardiomyopathy.

Long-term hyperglycemia can lead to diabetic cardiomyopathy (DCM), a main lethal complication of diabetes. However, the mechanisms underlying DCM development have not been fully elucidated. Heat shock protein A12A (HSPA12A) is the atypic member of the Heat shock 70kDa protein family. In the present study, we found that the expression of HSPA12A was upregulated in the hearts of mice with streptozotocin-induced diabetes, while ablation of HSPA12A improved cardiac systolic and diastolic dysfunction and increased cumulative survival of diabetic mice. An increased expression of HSPA12A was also found in H9c2 cardiac cells following treatment with high glucose (HG), while overexpression of HSPA12A-enhanced the HG-induced cardiac cell death, as reflected by higher levels of propidium iodide cells, lactate dehydrogenase leakage, and caspase 3 cleavage. Moreover, the HG-induced increase of oxidative stress, as indicated by dihydroethidium staining, was exaggerated by HSPA12A overexpression. Further studies demonstrated that the HG-induced increases of protein kinase B and forkhead box transcription factors 1 phosphorylation were diminished by HSPA12A overexpression, while pharmacologically inhibition of protein kinase B further enhanced the HG-induced lactate dehydrogenase leakage in HSPA12A overexpressed cardiac cells. Together, the results suggest that hyperglycemia upregulated HSPA12A expression in cardiac cells, by which induced cell death to promote DCM development. Targeting HSPA12A may serve as a potential approach for DCM management.

Plasmodium falciparum heat shock proteins as antimalarial drug targets: An update.

Global efforts to eradicate malaria are threatened by multiple factors, particularly the emergence of antimalarial drug resistant strains of Plasmodium falciparum. Heat shock proteins (HSPs), particularly P. falciparum HSPs (PfHSPs), represent promising drug targets due to their essential roles in parasite survival and virulence across the various life cycle stages. Despite structural similarities between human and malarial HSPs posing challenges, there is substantial evidence for subtle differences that could be exploited for selective drug targeting. This review provides an update on the potential of targeting various PfHSP families (particularly PfHSP40, PfHSP70, and PfHSP90) and their interactions within PfHSP complexes as a strategy to develop new antimalarial drugs. In addition, the need for a deeper understanding of the role of HSP complexes at the host-parasite interface is highlighted, especially heterologous partnerships between human and malarial HSPs, as this opens novel opportunities for targeting protein-protein interactions crucial for malaria parasite survival and pathogenesis.

Ascorbic acid mitigates the impact of oxidative stress in a human model of febrile seizure and mesial temporal lobe epilepsy.

Prolonged febrile seizures (FS) in children are linked to the development of temporal lobe epilepsy (MTLE). The association between these two pathologies may be ascribed to the long-term effects that FS exert on neural stem cells, negatively affecting the generation of new neurons. Among the insults associated with FS, oxidative stress is noteworthy. Here, we investigated the consequences of exposure to hydrogen peroxide (H2O2) in an induced pluripotent stem cell-derived neural stem cells (iNSCs) model of a patient affected by FS and MTLE. In our study, we compare the findings from the MTLE patient with those derived from iNSCs of a sibling exhibiting a milder phenotype defined only by FS, as well as a healthy individual. In response to H2O2 treatment, iNSCs derived from MTLE patients demonstrated an elevated production of reactive oxygen species and increased apoptosis, despite the higher expression levels of antioxidant genes and proteins compared to other cell lines analysed. Among the potential causative mechanisms of enhanced vulnerability of MTLE patient iNSCs to oxidative stress, we found that these cells express low levels of the heat shock protein HSPB1 and of the autophagy adaptor SQSTM1/p62. Pre-treatment of diseased iNSCs with the antioxidant molecule ascorbic acid restored HSBP1 and p62 expression and simultaneously reduced the levels of ROS and apoptosis. Our findings suggest the potential for rescuing the impaired oxidative stress response in diseased iNSCs through antioxidant treatment, offering a promising mechanism to prevent FS degeneration in MTLE.

Lack of the Histone Deacetylase SIRT1 Leads to Protection against Endoplasmic Reticulum Stress through the Upregulation of Heat Shock Proteins.

Histone deacetylase SIRT1 represses gene expression through the deacetylation of histones and transcription factors and is involved in the protective cell response to stress and aging. However, upon endoplasmic reticulum (ER) stress, SIRT1 impairs the IRE1α branch of the unfolded protein response (UPR) through the inhibition of the transcriptional activity of XBP-1 and SIRT1 deficiency is beneficial under these conditions. We hypothesized that SIRT1 deficiency may unlock the blockade of transcription factors unrelated to the UPR promoting the synthesis of chaperones and improving the stability of immature proteins or triggering the clearance of unfolded proteins. SIRT1+/+ and SIRT1-/- fibroblasts were exposed to the ER stress inducer tunicamycin and cell survival and expression of heat shock proteins were analyzed 24 h after the treatment. We observed that SIRT1 loss significantly reduced cell sensitivity to ER stress and showed that SIRT1-/- but not SIRT1+/+ cells constitutively expressed high levels of phospho-STAT3 and heat shock proteins. Hsp70 silencing in SIRT1-/- cells abolished the resistance to ER stress. Furthermore, accumulation of ubiquitinated proteins was lower in SIRT1-/- than in SIRT1+/+ cells. Our data showed that SIRT1 deficiency enabled chaperones upregulation and boosted the proteasome activity, two processes that are beneficial for coping with ER stress.

Heat shock proteins as a key defense mechanism in poultry production under heat stress conditions.

Over the past years, the poultry industry has been assigned to greater production performance but has become highly sensitive to environmental changes. The average world temperature has recently risen and is predicted to continue rising. In open-sided houses, poultry species confront high outside temperatures, which cause heat stress (HS) problems. Cellular responses are vital in poultry, as they may lead to identifying confirmed HS biomarkers. Heat shock proteins (HSP) are highly preserved protein families that play a significant role in cell function and cytoprotection against various stressors, including HS. The optimal response in which the cell survives the HS elevates HSP levels that prevent cellular proteins from damage caused by HS. The HSP have chaperonic action to ensure that stress-denatured proteins are folded, unfolded, and refolded. The HSP70 and HSP90 are the primary HSP in poultry with a defensive function during HS. HSP70 was the optimal biological marker for assessing HS among the HSP studied. The current review attempts to ascertain the value of HSP as a heat stress defense mechanism in poultry.

Reactive astrocytes secrete the chaperone HSPB1 to mediate neuroprotection.

Molecular chaperones are protective in neurodegenerative diseases by preventing protein misfolding and aggregation, such as extracellular amyloid plaques and intracellular tau neurofibrillary tangles in Alzheimer's disease (AD). In addition, AD is characterized by an increase in astrocyte reactivity. The chaperone HSPB1 has been proposed as a marker for reactive astrocytes; however, its astrocytic functions in neurodegeneration remain to be elucidated. Here, we identify that HSPB1 is secreted from astrocytes to exert non-cell-autonomous protective functions. We show that in human AD brain, HSPB1 levels increase in astrocytes that cluster around amyloid plaques, as well as in the adjacent extracellular space. Moreover, in conditions that mimic an inflammatory reactive response, astrocytes increase HSPB1 secretion. Concomitantly, astrocytes and neurons can uptake astrocyte-secreted HSPB1, which is accompanied by an attenuation of the inflammatory response in reactive astrocytes and reduced pathological tau inclusions. Our findings highlight a protective mechanism in disease conditions that encompasses the secretion of a chaperone typically regarded as intracellular.

Transcriptional modulation of heat shock proteins and adipogenic regulators in bovine adipocytes following heat exposure.

This research endeavored to elucidate the transcriptional modulation of heat shock proteins and adipogenic regulators in bovine subcutaneous adipocytes following thermal exposure. Post-differentiation, mature adipocytes were subjected to three treatments of control (CON), moderate (MHS), and extreme (EHS) heat stress. These treatments consist of thermal conditions at temperatures of 38 °C (CON), 39.5 °C (MHS), or 41 °C (EHS) along with of 3 or 12 h. There was no statistically significant variations observed in the gene expressions of HSP27 and HSP70 when comparing CON with MHS across both exposures. Contrastingly, when comparing CON with EHS, an upregulation (P < 0.01) in HSP27 gene expression was evident for both 3 and 12 h of incubation, while HSP70 gene expression exhibited elevation (P < 0.01) at the 3-h mark, with no change observed at 12 h. Protein quantification, however, revealed an elevation (P < 0.01) in HSP27 and HSP70 for both CON vs. MHS and CON vs. EHS at the 12-h exposure. This trend in protein level mirrored (P < 0.05) that of proliferator-activated receptor-gamma (PPARγ). Elevated (P < 0.05) protein levels of fatty acid synthase (FAS) were exclusively discernible in the CON vs. MHS. Increased (P < 0.01) transcriptional activity of PPARγ, CCAAT/enhancer-binding protein alpha (C/EBPα), stearoyl-CoA desaturase (SCD), and FAS was evident in the CON vs. EHS comparison. Complementary to these molecular findings, an augmented lipid droplet accumulation was observed (P < 0.01) in EHS-exposed adipocytes progressively from day 6 through day 9. Our current study highlights how different levels and lengths of heat stress can impact the activity of important heat-related proteins and factors that play a role in fat development in beef cattle. These findings can help guide strategies to manage how beef cattle are exposed to heat, which can affect fat storage and ultimately the quality of the meat's marbling.

Exploring Host-Guest Interactions within a 600 kDa DegP Protease Cage Complex Using Hydrodynamics Measurements and Methyl-TROSY NMR.

The DegP protease-chaperone operates within the periplasm of Gram-negative bacteria, where it assists in the regulation of protein homeostasis, promotes virulence, and is essential to survival under stress. To carry out these tasks, DegP forms a network of preorganized apo oligomers that facilitate the capture of substrates within distributions of cage-like complexes which expand to encapsulate clients of various sizes. Although the architectures of DegP cage complexes are well understood, little is known about the structures, dynamics, and interactions of client proteins within DegP cages and the relationship between client structural dynamics and function. Here, we probe host-guest interactions within a 600 kDa DegP cage complex throughout the DegP activation cycle using a model α-helical client protein through a combination of hydrodynamics measurements, methyl-transverse relaxation optimized spectroscopy-based solution nuclear magnetic resonance studies, and proteolytic activity assays. We find that in the presence of the client, DegP cages assemble cooperatively with few intermediates. Our data further show that the N-terminal half of the bound client, which projects into the interior of the cages, is predominantly unfolded and flexible, and exchanges between multiple conformational states over a wide range of time scales. Finally, we show that a concerted structural transition of the protease domains of DegP occurs upon client engagement, leading to activation. Together, our findings support a model of DegP as a highly cooperative and dynamic molecular machine that stabilizes unfolded states of clients, primarily via interactions with their C-termini, giving rise to efficient cleavage.

Heat Shock Proteins as Potential Indicators of Induced Stress in Nematodes.

Heat shock proteins (HSPs) in all animals studied to date constitute potential indicators of stress, under various environmental conditions. The goal of this chapter is to show, for the first time, the suitability of the approach based on evaluation of the expression levels of heat shock proteins, as good indicators of stress induced in nematodes by the cultivation of resistant plant varieties or by other potential stressors.

Elevated external temperature affects cell ultrastructure and heat shock proteins (HSPs) in Paramacrobiotus experimentalis Kaczmarek, Mioduchowska, Poprawa, & Roszkowska, 2020.

Increasing temperature influences the habitats of various organisms, including microscopic invertebrates. To gain insight into temperature-dependent changes in tardigrades, we isolated storage cells exposed to various temperatures and conducted biochemical and ultrastructural analysis in active and tun-state Paramacrobiotus experimentalis Kaczmarek, Mioduchowska, Poprawa, & Roszkowska, 2020. The abundance of heat shock proteins (HSPs) and ultrastructure of the storage cells were examined at different temperatures (20 °C, 30 °C, 35 °C, 37 °C, 40 °C, and 42 °C) in storage cells isolated from active specimens of Pam. experimentalis. In the active animals, upon increase in external temperature, we observed an increase in the levels of HSPs (HSP27, HSP60, and HSP70). Furthermore, the number of ultrastructural changes in storage cells increased with increasing temperature. Cellular organelles, such as mitochondria and the rough endoplasmic reticulum, gradually degenerated. At 42 °C, cell death occurred by necrosis. Apart from the higher electron density of the karyoplasm and the accumulation of electron-dense material in some mitochondria (at 42 °C), almost no changes were observed in the ultrastructure of tun storage cells exposed to different temperatures. We concluded that desiccated (tun-state) are resistant to high temperatures, but not active tardigrades (survival rates of tuns after 24 h of rehydration: 93.3% at 20 °C, 60.0% at 35 °C, 33.3% at 37 °C, 33.3% at 40 °C, and 20.0% at 42 °C).

Fungal heat shock proteins: molecular phylogenetic insights into the host takeover.

Heat shock proteins are constitutively expressed chaperones induced by cellular stress, such as changes in temperature, pH, and osmolarity. These proteins, present in all organisms, are highly conserved and are recruited for the assembly of protein complexes, transport, and compartmentalization of molecules. In fungi, these proteins are related to their adaptation to the environment, their evolutionary success in acquiring new hosts, and regulation of virulence and resistance factors. These characteristics are interesting for assessment of the host adaptability and ecological transitions, given the emergence of infections by these microorganisms. Based on phylogenetic inferences, we compared the sequences of HSP9, HSP12, HSP30, HSP40, HSP70, HSP90, and HSP110 to elucidate the evolutionary relationships of different fungal organisms to suggest evolutionary patterns employing the maximum likelihood method. By the different reconstructions, our inference supports the hypothesis that these classes of proteins are associated with pathogenic gains against endothermic hosts, as well as adaptations for phytopathogenic fungi.

HDX-MS finds that partial unfolding with sequential domain activation controls condensation of a cellular stress marker.

Eukaryotic cells form condensates to sense and adapt to their environment [S. F. Banani, H. O. Lee, A. A. Hyman, M. K. Rosen, Nat. Rev. Mol. Cell Biol. 18, 285-298 (2017), H. Yoo, C. Triandafillou, D. A. Drummond, J. Biol. Chem. 294, 7151-7159 (2019)]. Poly(A)-binding protein (Pab1), a canonical stress granule marker, condenses upon heat shock or starvation, promoting adaptation [J. A. Riback et al., Cell 168, 1028-1040.e19 (2017)]. The molecular basis of condensation has remained elusive due to a dearth of techniques to probe structure directly in condensates. We apply hydrogen-deuterium exchange/mass spectrometry to investigate the mechanism of Pab1's condensation. Pab1's four RNA recognition motifs (RRMs) undergo different levels of partial unfolding upon condensation, and the changes are similar for thermal and pH stresses. Although structural heterogeneity is observed, the ability of MS to describe populations allows us to identify which regions contribute to the condensate's interaction network. Our data yield a picture of Pab1's stress-triggered condensation, which we term sequential activation (Fig. 1A), wherein each RRM becomes activated at a temperature where it partially unfolds and associates with other likewise activated RRMs to form the condensate. Subsequent association is dictated more by the underlying free energy surface than specific interactions, an effect we refer to as thermodynamic specificity. Our study represents an advance for elucidating the interactions that drive condensation. Furthermore, our findings demonstrate how condensation can use thermodynamic specificity to perform an acute response to multiple stresses, a potentially general mechanism for stress-responsive proteins.

Distinct induction pathways of heat shock protein 27 in human keratinocytes: Heat stimulation or capsaicin through phosphorylation of heat shock factor 1 at serine 326 and/or suppression of ΔNp63.

Epidermal keratinocytes, forming the outermost layer of the human body, serve as a crucial barrier against diverse external stressors such as ultraviolet radiation. Proper keratinocyte differentiation and effective responses to external stimuli are pivotal for maintaining barrier integrity. Heat is one such stimulus that triggers the synthesis of heat shock proteins (HSPs) when cells are exposed to temperatures above 42 °C. Additionally, activation of the transient receptor potential cation channel subfamily V member 1 (TRPV1) occurs at 42 °C. Here, we explore the interplay between TRPV1 signaling and HSP induction in human keratinocytes. Both heat and capsaicin, a TRPV1 agonist, induce expression of HSP27, HSP70, and HSP90 in keratinocytes. Interestingly, pharmacological inhibition of TRPV1 attenuates heat-induced HSP27 expression, but not that of HSP70 or HSP90. Furthermore, both heat and capsaicin stimulation result in distinct phosphorylation patterns of heat shock factor 1 (HSF1), with phosphorylation at serine 326 being a common feature. Notably, genetic manipulation to mimic dephosphorylation of HSF1 at serine 326 reduces HSP27 levels. Additionally, ΔNp63, a key regulator of epidermal differentiation, negatively modulates HSP27 expression independently of HSF1 phosphorylation status. While heat stimulation has no effect on ΔNp63 expression, capsaicin reduces its levels. The precise role of TRPV1 signaling in keratinocytes warrants further investigation for a comprehensive understanding of its impact on barrier function.

Heat shock protein gp96 drives natural killer cell maturation and anti-tumor immunity by counteracting Trim28 to stabilize Eomes.

The maturation process of natural killer (NK) cells, which is regulated by multiple transcription factors, determines their functionality, but few checkpoints specifically targeting this process have been thoroughly studied. Here we show that NK-specific deficiency of glucose-regulated protein 94 (gp96) leads to decreased maturation of NK cells in mice. These gp96-deficient NK cells exhibit undermined activation, cytotoxicity and IFN-γ production upon stimulation, as well as weakened responses to IL-15 for NK cell maturation, in vitro. In vivo, NK-specific gp96-deficient mice show increased tumor growth. Mechanistically, we identify Eomes as the downstream transcription factor, with gp96 binding to Trim28 to prevent Trim28-mediated ubiquitination and degradation of Eomes. Our study thus suggests the gp96-Trim28-Eomes axis to be an important regulator for NK cell maturation and cancer surveillance in mice.

Heat Shock Protein 22 Attenuates Nerve Injury-induced Neuropathic Pain Via Improving Mitochondrial Biogenesis and Reducing Oxidative Stress Mediated By Spinal AMPK/PGC-1α Pathway in Male Rats.

Heat shock protein 22 (hsp22) plays a significant role in mitochondrial biogenesis and redox balance. Moreover, it's well accepted that the impairment of mitochondrial biogenesis and redox imbalance contributes to the progress of neuropathic pain. However, there is no available evidence indicating that hsp22 can ameliorate mechanical allodynia and thermal hyperalgesia, sustain mitochondrial biogenesis and redox balance in rats with neuropathic pain. In this study, pain behavioral test, western blotting, immunofluorescence staining, quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and Dihydroethidium staining are applied to confirm the role of hsp22 in a male rat model of spared nerve injury (SNI). Our results indicate that hsp22 was significantly decreased in spinal neurons post SNI. Moreover, it was found that intrathecal injection (i.t.) with recombinant heat shock protein 22 protein (rhsp22) ameliorated mechanical allodynia and thermal hyperalgesia, facilitated nuclear respiratory factor 1 (NRF1)/ mitochondrial transcription factor A (TFAM)-dependent mitochondrial biogenesis, decreased the level of reactive oxygen species (ROS), and suppressed oxidative stress via activation of spinal adenosine 5'monophosphate-activated protein kinase (AMPK)/ peroxisome proliferative activated receptor γ coactivator 1α (PGC-1α) pathway in male rats with SNI. Furthermore, it was also demonstrated that AMPK antagonist (compound C, CC) or PGC-1α siRNA reversed the improved mechanical allodynia and thermal hyperalgesia, mitochondrial biogenesis, oxidative stress, and the decreased ROS induced by rhsp22 in male rats with SNI. These results revealed that hsp22 alleviated mechanical allodynia and thermal hyperalgesia, improved the impairment of NRF1/TFAM-dependent mitochondrial biogenesis, down-regulated the level of ROS, and mitigated oxidative stress through stimulating the spinal AMPK/PGC-1α pathway in male rats with SNI.

Bacterial heat shock protein: A new crosstalk between T lymphocyte and macrophage via JAK2/STAT1 pathway in bloodstream infection.

Bloodstream infection (BSI) refers to the infection of blood by pathogens. Severe immune response to BSI can lead to sepsis, a systemic infection leading to multiple organ dysfunction, coupled with drug resistance, mortality, and limited clinical treatment options. This work aims to further investigate the new interplay between bacterial exocrine regulatory protein and host immune cells in the context of highly drug-resistant malignant BSI. Whether interfering with related regulatory signaling pathways can reverse the inflammatory disorder of immune cells. In-depth analysis of single-cell sequencing results in Septic patients for potential immunodeficiency factors. Analysis of key proteins enriched by host cells and key pathways using proteomics. Cell models and animal models validate the pathological effects of DnaK on T cells, MAITs, macrophages, and osteoclasts. The blood of patients was analyzed for the immunosuppression of T cells and MAITs. We identified that S. maltophilia-DnaK was enriched in immunodeficient T cells. The activation of the JAK2/STAT1 axis initiated the exhaustion of T cells. Septic patients with Gram-negative bacterial infections exhibited deficiencies in MAITs, which correspond to IFN-γ. Cellular and animal experiments confirmed that DnaK could facilitate MAIT depletion and M1 polarization of macrophages. Additionally, Fludarabine mitigated M1 polarization of blood, liver, and spleen in mice. Interestingly, DnaK also repressed osteoclastogenesis of macrophages stimulated by RANKL. S.maltophilia-DnaK prompts the activation of the JAK2/STAT1 axis in T cells and the M1 polarization of macrophages. Targeting the DnaK's crosstalk can be a potentially effective approach for treating the inflammatory disorder in the broad-spectrum drug-resistant BSI.

Intestinal heat shock proteins in metabolic syndrome: Novel mediators of obesity and its comorbidities resolution after metabolic surgery.

Over the past 40 years, the prevalence of obesity has risen dramatically, reaching epidemic proportions. Metabolic surgery has proven to be highly effective in treating obesity, leading to significant improvements or complete resolution of obesity-related comorbidities. Research conducted in both animals and humans suggests that the metabolic benefits achieved through metabolic surgery cannot be solely attributed to weight loss. Indeed, there has been an increasing recognition of intestinal inflammation as a novel factor influencing obesity. The gastrointestinal tract is continuously exposed to dietary components, particularly diets rich in saturated fats, which are known to contribute to obesity. It is now widely accepted that heat shock proteins can be released from various cells including intestinal epithelial cells and act as proinflammatory signals. Several studies have shown that circulating levels of glucose-regulated protein 78 (GRP78) are increased in subjects with obesity and correlate with the severity of the disease. Moreover, mice with a partial knockout of GRP78 are protected from diet-induced obesity. In this review, we discuss the role of GRP78 in the development of obesity. Several evidence suggests that GRP78 can influence adipogenesis, lipid droplets stabilization, insulin resistance, and liver steatosis. We also provide an update on GRP78 regulation following metabolic surgery, focusing on the bypass of the small intestine as a key factor for GRP78 secretion. Finally, we discuss the potential role of monoclonal antibodies against GRP78 as a treatment for obesity.

Combination of Polygonatum Rhizoma and Scutellaria baicalensis triggers apoptosis through downregulation of PON3-induced mitochondrial damage and endoplasmic reticulum stress in A549 cells.

OBJECTIVE: Scutellaria baicalensis (SB) and Polygonatum Rhizoma (PR), two traditional Chinese medicines, are both known to suppress cancer. However, the mechanism and effect of combined treatment of them for lung cancer are rarely known. Investigating the combined effect of SB and PR (hereafter referred to as SP) in potential mechanism of lung cancer is required. This study was to evaluate the inhibitory effects of SP on A549 cell growth and to explore the underlying molecular mechanisms. METHODS: According to the theory of Chinese medicine and network pharmacology, in the in vivo experiment, a mouse model of carcinoma in situ was constructed, and lung carcinoma in situ tissues were collected for proteomics analysis, hematoxylin-eosin staining, and CK19 immunohistochemistry. In the in vitro experiment, lung cancer A549 cells at logarithmic growth stage were taken, and the inhibitory effect of SP on the proliferation of A549 cells was detected by CCK8 method. The expression of PON3 was detected by quantitative polymerase chain reaction and western blot. In addition, the effect of SP on the induction of apoptosis in A549 cells and the changes of membrane potential and reactive oxygen species (ROS) content were detected by flow cytometry. The changes of PON3 content in endoplasmic reticulum (ER) are observed by laser confocal microscopy, whereas the effects of SP on the expression of apoptosis-related proteins and ER stress-related proteins in A549 cells were examined by western blot. RESULT: By searching the Traditional Chinese Medicines of Systems Pharmacology (TCMSP) (https://www.tcmspe.com/index.php) database and SymMap database, the respective target genes of PR and SB were mapped into protein network interactions, and using Venn diagrams to show 38 genes in common between PR and SB and lung cancer, SP was found to play a role in the treatment of lung cancer. In vivo experiments showed that in a lung carcinoma in situ model, lung tumor tissue was significantly lower in the SP group compared with the control group, and PON3 was shown to be downregulated by lung tissue proteomics analysis. The combination of SP was able to inhibit the proliferation of A549 cells in a concentration-dependent manner (p < .0001). The expression levels of apoptosis-related proteins and ER stress proteins were significantly increased and the expression levels of PON3 and anti-apoptosis-related proteins were decreased in A549 cells. At the same time, knockdown of PON3 could inhibit tumor cell proliferation (p < .0001). The combination of different concentrations of SP significantly induced apoptosis in A549 cells (p < .05; p < .0001), increased ROS content (p < .01), and damaged mitochondrial membrane potential of A549 cells (p < .05; p < .0001), and significantly increased the expression levels of apoptosis-related proteins and ER stress proteins in lung cancer A549 cells. CONCLUSION: SP inhibits proliferation of lung cancer A549 cells by downregulating PON3-induced apoptosis in the mitochondrial and ER pathways.