The Pathophysiological Role of Heat Shock Response in Autoimmunity: A Literature Review

Chaperones vs. oxidative stress in the pathobiology of ischemic stroke

As many proteins prioritize functionality over constancy of structure, a proteome is the shortest stave in the Liebig's barrel of cell sustainability. In this regard, both prokaryotes and eukaryotes possess abundant machinery supporting the quality of the proteome in healthy and stressful conditions. This machinery, namely chaperones, assists in folding, refolding, and the utilization of client proteins. The functions of chaperones are especially important for brain cells, which are highly sophisticated in terms of structural and functional organization. Molecular chaperones are known to exert beneficial effects in many brain diseases including one of the most threatening and widespread brain pathologies, ischemic stroke. However, whether and how they exert the antioxidant defense in stroke remains unclear. Herein, we discuss the chaperones shown to fight oxidative stress and the mechanisms of their antioxidant action. In ischemic stroke, during intense production of free radicals, molecular chaperones preserve the proteome by interacting with oxidized proteins, regulating imbalanced mitochondrial function, and directly fighting oxidative stress. For instance, cells recruit Hsp60 and Hsp70 to provide proper folding of newly synthesized proteins-these factors are required for early ischemic response and to refold damaged polypeptides. Additionally, Hsp70 upregulates some dedicated antioxidant pathways such as FOXO3 signaling. Small HSPs decrease oxidative stress via attenuation of mitochondrial function through their involvement in the regulation of Nrf- (Hsp22), Akt and Hippo (Hsp27) signaling pathways as well as mitophagy (Hsp27, Hsp22). A similar function has also been proposed for the Sigma-1 receptor, contributing to the regulation of mitochondrial function. Some chaperones can prevent excessive formation of reactive oxygen species whereas Hsp90 is suggested to be responsible for pro-oxidant effects in ischemic stroke. Finally, heat-resistant obscure proteins (Hero) are able to shield client proteins, thus preventing their possible over oxidation.

Current biomarkers and treatment strategies in Alzheimer disease: An overview and future perspectives

Alzheimer's disease (AD), a progressive degenerative disorder first identified by Alois Alzheimer in 1907, poses a significant public health challenge. Despite its prevalence and impact, there is currently no definitive ante mortem diagnosis for AD pathogenesis. By 2050, the United States may face a staggering 13.8 million AD patients. This review provides a concise summary of current AD biomarkers, available treatments, and potential future therapeutic approaches. The review begins by outlining existing drug targets and mechanisms in AD, along with a discussion of current treatment options. We explore various approaches targeting Amyloid β (Aβ), Tau Protein aggregation, Tau Kinases, Glycogen Synthase kinase-3β, CDK-5 inhibitors, Heat Shock Proteins (HSP), oxidative stress, inflammation, metals, Apolipoprotein E (ApoE) modulators, and Notch signaling. Additionally, we examine the historical use of Estradiol (E2) as an AD therapy, as well as the outcomes of Randomized Controlled Trials (RCTs) that evaluated antioxidants (e.g., vitamin E) and omega-3 polyunsaturated fatty acids as alternative treatment options. Notably, positive effects of docosahexaenoic acid nutriment in older adults with cognitive impairment or AD are highlighted. Furthermore, this review offers insights into ongoing clinical trials and potential therapies, shedding light on the dynamic research landscape in AD treatment.

Interplay between the Chaperone System and Gut Microbiota Dysbiosis in Systemic Lupus Erythematosus Pathogenesis: Is Molecular Mimicry the Missing Link between Those Two Factors?

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease characterized by self-immune tolerance breakdown and the production of autoantibodies, causing the deposition of immune complexes and triggering inflammation and immune-mediated damage. SLE pathogenesis involves genetic predisposition and a combination of environmental factors. Clinical manifestations are variable, making an early diagnosis challenging. Heat shock proteins (Hsps), belonging to the chaperone system, interact with the immune system, acting as pro-inflammatory factors, autoantigens, as well as immune tolerance promoters. Increased levels of some Hsps and the production of autoantibodies against them are correlated with SLE onset and progression. The production of these autoantibodies has been attributed to molecular mimicry, occurring upon viral and bacterial infections, since they are evolutionary highly conserved. Gut microbiota dysbiosis has been associated with the occurrence and severity of SLE. Numerous findings suggest that proteins and metabolites of commensal bacteria can mimic autoantigens, inducing autoimmunity, because of molecular mimicry. Here, we propose that shared epitopes between human Hsps and those of gut commensal bacteria cause the production of anti-Hsp autoantibodies that cross-react with human molecules, contributing to SLE pathogenesis. Thus, the involvement of the chaperone system, gut microbiota dysbiosis, and molecular mimicry in SLE ought to be coordinately studied.

The complement system as a key modulator of the oral microbiome in health and disease

In this review, we address the interplay between the complement system and host microbiomes in health and disease, focussing on oral bacteria known to contribute to homeostasis or to promote dysbiosis associated with dental caries and periodontal diseases. Host proteins modulating complement activities in the oral environment and expression profiles of complement proteins in oral tissues were described. In addition, we highlight a sub-set of bacterial proteins involved in complement evasion and/or dysregulation previously characterized in pathogenic species (or strains), but further conserved among prototypical commensal species of the oral microbiome. Potential roles of these proteins in host-microbiome homeostasis and in the emergence of commensal strain lineages with increased virulence were also addressed. Finally, we provide examples of how commensal bacteria might exploit the complement system in competitive or cooperative interactions within the complex microbial communities of oral biofilms. These issues highlight the need for studies investigating the effects of the complement system on bacterial behaviour and competitiveness during their complex interactions within oral and extra-oral host sites.

Introducing Molecular Chaperones into the Causality and Prospective Management of Autoimmune Hepatitis

Molecular chaperones influence the immunogenicity of peptides and the activation of effector T cells, and their pathogenic roles in autoimmune hepatitis are unclear. Heat shock proteins are pivotal in the processing and presentation of peptides that activate CD8+ T cells. They can also induce regulatory B and T cells and promote immune tolerance. Tapasin and the transporter associated with antigen processing-binding protein influence the editing and loading of high-affinity peptides for presentation by class I molecules of the major histocompatibility complex. Their over-expression could enhance the autoimmune response, and their deficiency could weaken it. The lysosome-associated membrane protein-2a isoform in conjunction with heat shock cognate 70 supports the importation of cytosolic proteins into lysosomes. Chaperone-mediated autophagy can then process the peptides for activation of CD4+ T cells. Over-expression of autophagy in T cells may also eliminate negative regulators of their activity. The human leukocyte antigen B-associated transcript three facilitates the expression of class II peptide receptors, inhibits T cell apoptosis, prevents T cell exhaustion, and sustains the immune response. Immunization with heat shock proteins has induced immune tolerance in experimental models and humans with autoimmune disease by inducing regulatory T cells. Therapeutic manipulation of other molecular chaperones may promote T cell exhaustion and induce tolerogenic dendritic cells. In conclusion, molecular chaperones constitute an under-evaluated family of ancillary proteins that could affect the occurrence, severity, and outcome of autoimmune hepatitis. Clarification of their contributions to the immune mechanisms and clinical activity of autoimmune hepatitis could have therapeutic implications.

Progesterone modulates extracellular heat-shock proteins and interlukin-1β in human choriodecidual after Escherichia coli infection

INTRODUCTION

Chorioamnionitis is an adverse condition in human pregnancy caused by many bacterial pathogens including Escherichia coli (E. coli); which has been associated with higher risk of preterm birth. We recently reported that human maternal decidua (MDec) tissue responds to E. coli infection by secreting extracellular heat-shock proteins (eHsp)-60, -70 and interlukin-1β (IL-1β). Previous studies have shown that progesterone (P4) regulates the immune response, but it is unknown whether P4 inhibits the secretion of eHsp. The aim of this investigation was to determine the role of P4 on the secretion of eHsp-27, -60, -70 and IL-1β in MDec after 3, 6, and 24 h of E. coli infection.

METHODS

Nine human feto-maternal interface (HFMi) tissues were included and mounted in the Transwell culture system. Only the maternal decidua (MDec) was stimulated for 3, 6 and 24 h with E. coli alone or in combination with progesterone and RU486. After each treatment, the HFMi tissue was recovered to determine histological changes and the culture medium recovered to evaluate the levels of eHsp-27, -60, -70 and IL-1β by ELISA and mRNA expression by RT-PCR.

RESULTS

No structural changes were observed in the HFMi tissue treated with P4 and RU486. However, stimulation with E. coli produces diffuse inflammation and ischemic necrosis. E. coli induced infection decreases, in time- and dose-dependent manner, eHsp-27 and increases eHsp-60, eHsp-70 and IL-1β levels. In contrast, incubation of HFMi tissue with E. coli + P4 reversed eHsp and IL-1β secretion levels relative to E. coli stimulation group but not relative to the control group. The same profile was observed on the expression of eHsp-27 and eHsp-60.

DISCUSSION

we found that progesterone modulates the anti-inflammatory (eHsp-27) and pro-inflammatory (eHsp-60 and eHsp-70) levels of eHsp induced by E. coli infection in human choriodecidual tissue. eHsp-60 and eHsp-70 levels were not completely reversed; maintaining the secretion of IL-1β, which has been associated with adverse events during pregnancy.

Heat Shock Proteins in Behçet Syndrome

Behçet syndrome (BS) is a systemic vasculitis of unknown etiology that affects the skin, mucosa, joints, eyes, central nervous system, gastrointestinal system, arteries, and veins. It is generally believed to have a complex genetic background where both innate and adaptive immune systems are activated through environmental factors, such as infections, and auto-antigens. Heat shock proteins (HSPs) are highly conserved and immunogenic endogenous proteins that are thought to play both an enhancing and regulating role in several autoimmune and inflammatory diseases, such as rheumatoid arthritis, juvenile idiopathic arthritis, and Type I diabetes. There is evidence supporting the role of various microorganisms in BS, which may be using a common pathway to trigger or activate BS through molecular mimicry. The significant homology between microbial and human HSPs suggests that HSPs could serve as a common trigger. This review summarizes the work on the role of HSPs in the pathogenesis of BS. However, it remains unknown whether the HSPs detected in BS lesions play a causative role, their presence is a result of the ongoing inflammation, or they have a protective role against inflammation, as suggested in some other diseases.

Proteome analysis, bioinformatic prediction and experimental evidence revealed immune response down-regulation function for serum-starved human fibroblasts

Emerging evidence indicates that fibroblasts play pivotal roles in immunoregulation by producing various proteins under health and disease states. In the present study, for the first time, we compared the proteomes of serum-starved human skin fibroblasts and peripheral blood mononuclear cells (PBMCs) using Nano-LC-ESI-tandem mass spectrometry. This analysis contributes to a better understanding of the underlying molecular mechanisms of chronic inflammation and cancer, which are intrinsically accompanied by growth factor deficiency.The proteomes of starved fibroblasts and PBMCs consisted of 307 and 294 proteins, respectively, which are involved in lymphocyte migration, complement activation, inflammation, acute phase response, and immune regulation. Starved fibroblasts predominantly produced extracellular matrix-related proteins such as collagen/collagenase, while PBMCs produced focal adhesion-related proteins like beta-parvin and vinculin which are involved in lymphocyte migration. PBMCs produced a more diverse set of inflammatory molecules like heat shock proteins, while fibroblasts produced human leukocytes antigen-G and -E that are known as main immunomodulatory molecules. Fifty-four proteins were commonly found in both proteomes, including serum albumin, amyloid-beta, heat shock cognate 71 kDa, and complement C3. GeneMANIA bioinformatic tool predicted 418 functions for PBMCs, including reactive oxygen species metabolic processes and 241 functions for starved fibroblasts such as antigen processing and presentation including non-classical MHC -Ib pathway, and negative regulation of the immune response. Protein-protein interactions network analysis indicated the immunosuppressive function for starved fibroblasts-derived human leucocytes antigen-G and -E. Moreover, in an in vitro model of allogeneic transplantation, the immunosuppressive activity of starved fibroblasts was experimentally documented.

Conclusion

Under serum starvation-induced metabolic stress, both PBMCs and fibroblasts produced molecules like heat shock proteins and amyloid-beta, which can have pathogenic roles in auto-inflammatory diseases such as rheumatoid arthritis, type 1 diabetes mellitus, systemic lupus erythematosus, aging, and cancer. However, starved fibroblasts showed immunosuppressive activity in an in vitro model of allogeneic transplantation, suggesting their potential to modify such adverse reactions by down-regulating the immune system.

Emerging roles of tyrosine kinases in hepatic inflammatory diseases and therapeutic opportunities

Inflammation has been convicted of causing and worsening many liver diseases like acute liver failure, fibrosis, cirrhosis, fatty liver and liver cancer. Pattern recognition receptors (PRRs) like TLRs 4 and 9 localized on resident or recruited immune cells are well known cellular detectors of pathogen and damage-associated molecular patterns (PAMPs/DAMPs). Stimulation of these receptors generates the sterile and non-sterile inflammatory responses in the liver. When these responses are repeated, there will be a sustained liver injury that may progress to fibrosis and its outcomes. Crosstalk between inflammatory/fibrogenic-dependent streams and certain tyrosine kinases (TKs) has recently evolved in the context of hepatic diseases. Because of TKs increasing importance, their role should be elucidated to highlight effective approaches to manage the diverse liver disorders. This review will give a brief overview of types and functions of some TKs like BTK, JAKs, Syk, PI3K, Src and c-Abl, as well as receptors for TAM, PDGF, EGF, VEGF and HGF. It will then move to discuss the roles of these TKs in the regulation of the proinflammatory, fibrogenic and tumorigenic responses in the liver. Lastly, the therapeutic opportunities for targeting TKs in hepatic inflammatory disorders will be addressed. Overall, this review sheds light on the diverse TKs that have substantial roles in hepatic disorders and potential therapeutics modulating their activity.

Incorporating the Molecular Mimicry of Environmental Antigens into the Causality of Autoimmune Hepatitis

Molecular mimicry between foreign and self-antigens has been implicated as a cause of autoimmune hepatitis in experimental models and cross-reacting antibodies in patients. This review describes the experimental and clinical evidence for molecular mimicry as a cause of autoimmune hepatitis, indicates the limitations and uncertainties of this premise, and encourages investigations that assess diverse environmental antigens as sources of disease-relevant molecular mimics. Pertinent articles were identified in PubMed using multiple search phrases. Several pathogens have linear or conformational epitopes that mimic the self-antigens of autoimmune hepatitis. The occurrence of an acute immune-mediated hepatitis after vaccination for severe acute respiratory syndrome (SARS)-associated coronavirus 2 (SARS-CoV-2) has suggested that vaccine-induced peptides may mimic disease-relevant tissue antigens. The intestinal microbiome is an under-evaluated source of gut-derived antigens that could also engage in molecular mimicry. Chaperone molecules may enhance the pathogenicity of molecular mimics, and they warrant investigation. Molecular mimics of immune dominant epitopes within cytochrome P450 IID6, the autoantigen most closely associated with autoimmune hepatitis, should be sought in diverse environmental antigens and assessed for pathogenicity. Avoidance strategies, dietary adjustments, vaccine improvement, and targeted manipulation of the intestinal microbiota may emerge as therapeutic possibilities. In conclusion, molecular mimicry may be a missing causality of autoimmune hepatitis. Molecular mimics of key immune dominant epitopes of disease-specific antigens must be sought in diverse environmental antigens. The ubiquity of molecular mimicry compels rigorous assessments of peptide mimics for immunogenicity and pathogenicity in experimental models. Molecular mimicry may complement epigenetic modifications as causative mechanisms of autoimmune hepatitis.

Complexity of the Immune Response Elicited by Different COVID-19 Vaccines, in the Light of Natural Autoantibodies and Immunomodulatory Therapies

Despite the abundance of data on the COVID-19 vaccine-induced immune activation, the impact of natural autoantibodies (nAAbs) on these processes is less well defined. Therefore, we investigated potential connections between vaccine efficacy and nAAb levels. We were also interested in the impact of immunomodulatory therapies on vaccine efficacy. Clinical residual samples were used for the assessment of the COVID-19 vaccine-elicited immune response (IR) (n=255), as well as for the investigation of the immunization-associated expansion of the nAAb pool (n=185). In order to study the potential interaction between immunomodulatory therapies and the vaccine-induced IR, untreated, healthy individuals and patients receiving anti-TNFα or anti-IL-17 therapies were compared (n total =45). In-house ELISAs (anticitrate synthase, anti-HSP60 and-70) and commercial ELISAs (anti-SARS-CoV-2 ELISAs IgG, IgA, NeutraLISA and IFN-γ release assay 'IGRA') were applied. We found significant differences in the IR given to different vaccines. Moreover, nAAb levels showed plasticity in response to anti-COVID-19 immunization. We conclude that our findings may support the theorem about the non-specific beneficial 'side effects' of vaccination, including the broadening of the nAAb repertoire. Considering immunomodulation, we suggest that anti-TNFα and anti-IL17 treatments may interfere negatively with MALT-associated IR, manifested as decreased IgA titers; however, the modest sample numbers of the herein presented model might be a limiting factor of reaching a more comprehensive conclusion.

HSP70 and Primary Arterial Hypertension

Heat shock protein 70 (HSP70) production is a stress-generated cellular response with high interspecies homology. HSP70 has both chaperone and cytokine functions and may induce, depending on the context, tolerogenic anti-inflammatory reactivity or immunogenic and autoimmune reactivity. Intracellular (chaperoning transit of antigens to MHC in antigen-presenting cells) and extracellular HSP70-related effects are associated with hypertension, which is an inflammatory condition recognized as the most important risk factor for cardiovascular disease mortality. Here, we review (a) the relationship between HSP70, inflammation and immune reactivity, (b) clinical evidence relating to stress, HSP70 and anti-HSP70 reactivity with primary hypertension and (c) experimental data showing that salt-sensitive hypertension is associated with delayed hypersensitivity to HSP70. This is a consequence of anti-HSP70 reactivity in the kidneys and may be prevented and corrected by the T-cell-driven inhibition of kidney inflammation triggered by specific epitopes of HSP70. Finally, we discuss our postulate that lifelong stress signals and danger-associated molecular patterns stimulate HSP-70 and individual genetic and epigenetic characteristics determine whether the HSP70 response would drive inflammatory immune reactivity causing hypertension or, alternatively, would drive immunomodulatory responses that protect against hypertension.

Exploring the immunomodulatory effects and mechanisms of Xinjiang fermented camel milk-derived bioactive peptides based on network pharmacology and molecular docking

Purpose: Fermented camel milk from Xinjiang is rich in probiotics and has immunomodulatory effects as an important source of bioactive peptides. However, it is not clear whether it is the probiotic or the bioactive peptide that acts. The present study aimed to extract and identify bioactive peptides from fermented camel milk in Xinjiang and investigate their immunomodulatory effects and mechanisms based on network pharmacology and molecular docking. Methods: Four probiotic bacteria were used to ferment the fresh camel milk and the bioactive peptides were extracted and isolated by ultrafiltration and column chromatography. Network pharmacology predicts targets and pathways of action. GeneCards and OMIM-GENE-MAP database were used in order to search disease target genes and screen common target genes. Then we used STRING web to construct a protein-protein interaction (PPI) interaction network of the common target protein. The key targets were analyzed by GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis through the David database. The "drug (bioactive peptide)-disease-targets-pathway" network was established and molecular docking was used for prediction. Results: Two fractions were obtained by UV spectrophotometer; whey acidic protein, α-lactalbumin, and peptidoglycan recognition protein 1 were the main protein-like components of Xinjiang fermented camel milk-derived bioactive peptides. The repeat sequence of peptidoglycan recognition protein 1 was selected and then seven bioactive peptides were obtained. Bioactive peptides had 222 gene targets, anti-inflammatory diseases had 2598 gene targets, and immune regulation had 866 gene targets, the intersection of which was 66 in common gene targets. Gene ontology and KEGG analysis reveals that bioactive peptides mainly play a vital role in the signaling pathways of lipid and atherosclerosis, pathways in cancer. The molecular docking results showed that the seven bioactive peptides bound well to the top four scoring proteins. Conclusion: The immunomodulatory and anti-inflammatory effects and mechanisms of Xinjiang fermented camel milk-derived bioactive peptides were initially investigated by network pharmacology and molecular docking, providing a scientific basis for future studies.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.