Heat-shock proteins in autoimmunity

Genome-wide identification of heat shock protein gene family and their responses to pathogen challenge in Trachinotus ovatus

Heat Shock Proteins (HSPs) are a widely distributed family of proteins produced in response to heat and other stresses. To develop a deeper understanding of the mechanisms governing expression of HSPs in the bony fish Trachinotus ovatus, we carried out a whole genome analysis and identified 43 HSP genes. Based on their phylogenetic relationships with Danio rerio, Seriola dumerili, and Seriola lalandi, they were divided into four subfamilies: HSP20, HSP60, HSP70, and HSP90. We performed an analysis of the predicted physicochemical properties and subcellular localization of proteins encoded by these genes. The chromosomal localization results showed that the HSP genes are distributed across 20 chromosomes of T. ovatus.These genes were found to be expressed in different tissues, and they showed differential expression in the immune response against Streptococcus agalactiae. However, there was no significant differential expression in the different skin tissue locations of T. ovatus after infection by Cryptocaryon irritans Brown. This study provides basic information for further research on the evolution and structure and function of HSPs in teleosts.

Infectious diseases, autoantibodies, and autoimmunity

Infections are known to trigger flares of autoimmune diseases in humans and serve as an inciting cause of autoimmunity in animals. Evidence suggests a causative role of infections in triggering antigen-specific autoimmunity, previous thought mainly through antigen mimicry. However, an infection can induce bystander autoreactive T and B cell polyclonal activation, believed to result in non-pathogenic and pathogenic autoimmune responses. Lastly, epitope spreading in autoimmunity is a mechanism of epitope changes of autoreactive cells induced by infection, promoting the targeting of additional self-epitopes. This review highlights recent research findings, emphasizes infection-mediated autoimmune responses, and discusses the possible mechanisms involved.

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.

Role of heat shock proteins in aging and chronic inflammatory diseases

Advanced age is associated with a decline in response to stress. This contributes to the establishment of chronic inflammation, one of the hallmarks of aging and age-related disease. Heat shock proteins (HSP) are determinants of life span, and their progressive malfunction leads to age-related pathology. To discuss the function of HSP on age-related chronic inflammation and illness. An updated review of literature and discussion of relevant work on the topic of HSP in normal aging and chronic inflammatory pathology was performed. HSP contribute to inflamm-aging. They also play a key role in age-associated pathology linked to chronic inflammation such as autoimmune disorders, neurological disease, cardiovascular disorder, and cancer. HSP may be targeted for control of their effects related to age and chronic inflammation. Research on HSP functions in age-linked chronic inflammatory disorders provides an opportunity to improve health span and delay age-related chronic disorders.

SARS-CoV-2 Infection and Guillain-Barré Syndrome: A Review on Potential Pathogenic Mechanisms

Since December 2019, the world has been facing an outbreak of a new disease called coronavirus disease 2019 (COVID-19). The COVID-19 pandemic is caused by a novel beta-coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 infection mainly affects the respiratory system. Recently, there have been some reports of extra-respiratory symptoms such as neurological manifestations in COVID-19. According to the increasing reports of Guillain-Barré syndrome following COVID-19, we mainly focused on SARS-CoV-2 infection and Guillain-Barré syndrome in this review. We tried to explain the possibility of a relationship between SARS-CoV-2 infection and Guillain-Barré syndrome and potential pathogenic mechanisms based on current and past knowledge.

SARS-CoV-2 and Guillain-Barré syndrome: molecular mimicry with human heat shock proteins as potential pathogenic mechanism

Severe acute respiratory syndrome-related coronavirus 2 infection has been associated with Guillain-Barré syndrome. We investigated here the potential mechanism underlying the virus-induced damage of the peripheral nervous systems by searching the viral amino acid sequence for peptides common to human autoantigens associated with immune-mediated polyneuropathies. Our results show molecular mimicry between the virus and human heat shock proteins 90 and 60, which are associated with Guillain-Barré syndrome and other autoimmune diseases. Crucially, the shared peptides are embedded in immunoreactive epitopes that have been experimentally validated in the human host.

Quantitative Proteomic Analyses To Reveal the Key Features of Proteins in New Onset Ankylosing Spondylitis Patients

Ankylosing spondylitis (AS) is a chronic immune-mediated disease. Various immune cells play an essential role in the AS pathogenesis. However, the specific pathogenesis of AS has not been well understood. Proteomic profiles of peripheral blood mononuclear cells (PBMCs) were applied to reveal the specific pathogenesis of AS. Quantitative proteomic analyses were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based methods to investigate the protein profiling of PBMCs from new-onset AS patients (n = 9) and healthy controls (n = 9). We identified 782 differentially expressed proteins (DEPs) and 527 differentially phosphorylated proteins (DPPs) between AS patients and healthy controls. The subcellular location of DEPs and DPPs showed that most of the DEPs were from the cytoplasm (n = 296, 38%), were extracellular (n = 141, 18%), and from the nucleus (n = 114, 15%); most of the DPPs were from the cytoplasm (n = 37, 34%), nucleus (n = 35, 32%), and plasma membrane (n = 10, 9%). We further identified 89 proteins with both expression and phosphorylation differences. The functional annotation of the 89 differentially expressed and phosphorylated proteins enriched in the antigen processing and presentation pathway. Four DEPs with six phosphorylated positions were found in the antigen processing and presentation pathway. The differentially expressed and phosphorylated proteins may be helpful to uncover the pathogenesis of AS. The six AS-specific proteins may serve as candidate markers for AS diagnosis and new treatment targets.

Past and Present Behçet's Disease Animal Models

Behçet's disease (BD) is presumably an autoinflammatory disease of unknown etiology for which several animal models have been described over the years. Agents and methods used for the development of these models have ranged from the herpes simplex type one virus (hsv-1) pathogen to the use of transgenic mice. Other models have also been used to investigate a possible autoimmune component. Each model possesses its own unique set of benefits and shortcomings, with no one model fully being able to recapitulate the disease phenotype. Here, we review the proposed models and provide commentary on their effectiveness and usefulness in studying the disease.

Serum heat-shock protein-65 antibody levels are elevated but not associated with disease activity in patients with rheumatoid arthritis and ankylosing spondylitis

Objectives

Heat-shock proteins (HSPs) have gained increased interest for their role in autoimmune disorders. These proteins are targeted by the immune system in various autoimmune diseases. The aim of this study was to assess the serum heat-shock protein-65 antibody (anti-HSP65) levels and their clinical significance in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS).

Patients and methods

A total of 30 patients with RA, 30 patients with AS, and 30 healthy controls were enrolled in this study. All patients were assessed using routine clinical and laboratory evaluations. Serum anti-HSP65 levels were determined by ELISA.

Results

Serum anti-HSP65 levels of both RA and AS patients were significantly higher than those of controls (p=0.014 and p=0.001, respectively). No association was found between serum anti-HSP65 levels and disease activity in either RA or AS patients. There was a significant correlation between anti-HSP65 and anti-cyclic citrullinated peptide levels in patients with RA (p=0.024).

Conclusion

In this study, serum anti-HSP65 levels were increased, but not associated with disease activity in both RA and AS patients. These results suggest that HSP antigens may play a role in the pathogenesis. However, further follow-up studies are needed. Identification of target antigens such as HSP65 is vital to developing new immunotherapeutic agents.

Modulation of Adjuvant Arthritis by Cellular and Humoral Immunity to Hsp65

Heat shock proteins (Hsps) are highly conserved, and their expression is upregulated in cells by heat and other stressful stimuli. These proteins play a vital role in preserving the structural and functional integrity of cells under stress. Despite the ubiquitous expression of Hsps in an individual, the immune system is not fully tolerant to them. In fact, Hsps are highly immunogenic in nature, and immune response to these proteins is observed in various inflammatory and autoimmune diseases. Studies on the immunopathogenesis of autoimmune arthritis in the rat adjuvant arthritis (AA) model of human rheumatoid arthritis (RA) as well as observations in patients with RA and juvenile idiopathic arthritis (JIA) have unraveled immunoregulatory attributes of self-Hsp65-directed immunity. Notable features of Hsp65 immunity in AA include protection rather than disease induction following immunization of Lewis rats with self (rat)-Hsp65; the diversification of T cell response to mycobacterial Hsp65 during the course of AA and its association with spontaneous induction of response to self-Hsp65; the cross-reactive T cells recognizing foreign and self homologs of Hsp65 and their role in disease suppression in rats; the suppressive effect of antibodies to Hsp65 in AA; and the use of Hsp65, its peptides, or altered peptide ligands in controlling autoimmune pathology. The results of studies in the AA model have relevance to RA and JIA. We believe that these insights into Hsp65 immunity would not only advance our understanding of the disease process in RA/JIA, but also lead to the development of novel therapeutic approaches for autoimmune arthritis.

Autoantibodies to Heat-Shock Protein, HSPA5, and Epitope Spreading: High-Dose Dexamethasone Therapy Rescues Ovarian Function in Experimental Autoimmune Ovarian Insufficiency Mouse Model

PROBLEM

Role of autoantibodies to heat-shock protein 70 isoform, HSPA5, both alone or in combination with other antigenic peptides in epitope spreading and effect of high-dose dexamethasone to overcome this.

METHOD OF STUDY

Experimental autoimmune premature ovarian insufficiency mouse model generated by immunization with immunodominant epitopes of HSPA5 alone or in combination with other antigenic peptides. Two doses of dexamethasone treatment are given to the latter group. Immunosorbent assay and Western blot analysis were undertaken to detect cross-reactivity. Hormonal estimations, histological evaluation, and fertility studies were performed to assess treatment efficacy.

RESULTS

One of the immunodominant epitopes of HSPA5 led to epitope spreading. Of the two doses, 100 mg was more effective in rescuing fertility.

CONCLUSIONS

We postulate that the shared immunodominant peptide could be included in a peptide array to detect both HSAP5 and HSP90β autoantibodies for early diagnosis or prognosis of aPOI and customized glucocorticoid therapy for such subjects.

The virus-induced HSPs regulate the apoptosis of operatus APCs that result in autoimmunity, not in homeostasis

The viruses stand salient as environmental factors that trigger autoimmunity. The virus realizes its effects through induction of heat-shock proteins (HSPs) as well as by the viral IE-axis-mediated conversion of organ epithelial cells into virgin de novo professional antigen-presenting cells (APCs). The HSP is the accomplished operator in homeostasis by the logic of it being the regulator of apoptosis. By virtue of its regulation of apoptosis, the HSP is also involved in autoimmunity: (1) adornment of viral IE-axis-generated virgin de novo professional APCs with HSP-induced co-stimulatory molecules which transform these otherwise epithelial cells to competent antigen presenters, the operatus APCs, liable to apoptosis that becomes the initiator of organ damages; (2) molecular mimicry mechanism: epitopes on the HSP may be mistaken for viral peptides and be presented by operatus APCs to autoreactive TCRs resulting in the apoptosis of the operatus APCs; (3) regulation of MHC class II DR-mediated apoptosis of operatus APCS which can result in organ-specific autoimmune syndromes. We should remember, however, that Nature's intended purpose for apoptosis of the professional APCs is benevolence: as a principal regulator of immune homeostasis. But the apoptosis of our postulated operatus APCs can result in autoimmunity. The transformation of virgin de novo professional APCs to operatus APCs mirrors the maturation of DCs through their acquisition of HSP-induced costimulatory molecules. What happens to mature DCs as antigen presenters that end in homeostasis is replicated by what happens to operatus APCs that ends instead in autoimmunity.

The wonderous chaperones: A highlight on therapeutics of cancer and potentially malignant disorders

Diverse environmental and physiological factors are known to induce the transcription of a set of genes encoding special protective molecules known as "molecular chaperones" within our cells. Literature abounds in evidence regarding the varied roles; these "guides" can effectively perform in our system. Highly conserved through evolution, from the prokaryotes to the eukaryotes, these make perfect study tools for verifying their role in both the pathogenesis as well as the therapeutics of varied neurodegenerative, autoimmune and potentially malignant disorders and varied cancer states. We present a concise review of this ever dynamic molecule, highlighting the probable role in a potentially malignant disorder, oral lichen planus.

The Extracellular IFI16 Protein Propagates Inflammation in Endothelial Cells Via p38 MAPK and NF-κB p65 Activation

The nuclear interferon-inducible-16 (IFI16) protein acts as DNA sensor in inflammasome signaling and as viral restriction factor. Following Herpesvirus infection or UV-B treatment, IFI16 delocalizes from the nucleus to the cytoplasm and is eventually released into the extracellular milieu. Recently, our group has demonstrated the occurrence of IFI16 in sera of systemic-autoimmune patients that hampers biological activity of endothelia through high-affinity membrane binding. As a continuation, we studied the activity of endotoxin-free recombinant IFI16 (rIFI16) protein on primary endothelial cells. rIFI16 caused dose/time-dependent upregulation of IL-6, IL-8, CCL2, CCL5, CCL20, ICAM1, VCAM1, and TLR4, while secretion of IL-6 and IL-8 was amplified with lipopolysaccharide synergy. Overall, cytokine secretion was completely inhibited in MyD88-silenced cells and partially by TLR4-neutralizing antibodies. By screening downstream signaling pathways, we found that IFI16 activates p38, p44/42 MAP kinases, and NF-kB. In particular, activation of p38 is an early event required for subsequent p44/42 MAP kinases activity and cytokine induction indicating a key role of this kinase in IFI16 signaling. Altogether, our data conclude that extracellular IFI16 protein alone or by synergy with lipopolysaccharide acts like Damage-associated molecular patterns propagating "Danger Signal" through MyD88-dependent TLR-pathway.

Humoral response against small heat shock proteins in Parkinson's disease

Introduction

In the light of evidence for the increased heat shock proteins (HSP) expression in neurodegenerative disorders, the presence of the adaptive humoral response of the immune system can be expected. The aim of the study was to check whether Parkinson’s disease (PD) has the ability to elicit immune response against small heat shock proteins.

Methods

IgG and IgM autoantibodies against alpha B-crystallin were assessed in 26 PD patients 26 healthy subjects. For the assessment of anti-HSP IgG autoantibodies serum samples from 31 parkinsonian patients and 31 healthy control subjects were collected. Serum samples from PD patients and healthy control subjects were collected twice, at baseline and after mean of 13 months follow up.

Results

Both IgM and IgG autoantibodies against alpha ß-crystallin in PD patients were significantly higher compared to healthy controls (p<0.05). We also found statistically significant increase in antibodies titers against alpha ß-crystallin over the time of 13 months, both for IgG (p = 0.021) and for IgM (p<0.0001). Additionally, PD patients presented higher levels of anti-HSP IgG autoantibodies than healthy controls (p = 0.02).

Conclusions

Increase of IgG and IgM autoantibodies against alpha B-crystallin in PD patients over time may suggest their involvement in the disease pathogenesis and progression. Further studies are required to confirm the role of this antibody as a biomarker of the disease progression.

The virus-induced HSPs regulate the apoptosis of operatus APCs that results in autoimmunity, not in homeostasis

The viruses are salient in the roles of environmental factors that trigger autoimmunity. The virus realizes its effects by the power of its induction of heat shock proteins (HSPs) as well as by the viral IE-axis-mediated conversion of organ epithelial cells into virgin de novo professional antigen-presenting cells (APCs). The HSP is the accomplished operator in homeostasis by the logic of it being the regulator of apoptosis. That HSP which regulates and controls different points in the pathways of apoptosis is rationally propitious as both HSP and apoptosis are highly conserved in multicellular organisms. By virtue of its regulation of apoptosis, the HSP is also involved in human autoimmunity and this involvement is tripartite: (i) adornment of viral IE-axis-generated virgin de novo professional APCs with HSP-induced co-stimulatory molecules which transform these otherwise epithelial cells to achieve the status of fledged competent antigen-presenters, the operatus APCs, which are liable to apoptosis that becomes the initiator of organ damages that can culminate in the autoimmune syndrome(s); apoptosis is a routine fate that befalls all APCs following their antigen presentation; (ii) molecular mimicry mechanism: epitopes on the HSP may be mistaken for viral peptides and be presented by operatus APCs to autoreactive TCRs resulting in the apoptosis of the operatus APCs; and (iii) regulation of MHC class II-DR-mediated apoptosis of operatus APCs which can ultimately consequent in organ-specific autoimmune syndromes. We should remember, however, that Nature's intended purpose for the apoptosis of the professional APCs is benevolence: as a principal regulator of homeostasis. It is only from the apoptosis of our postulated operatus APCs that the apoptotic consequence can be deleterious, an autoimmune syndrome(s). The transformation of virgin de novo professional APCs to operatus APCs mirrors the maturation of DCs, through their acquisition of HSP-induced co-stimulatory molecules; and what happens to mature DCs as antigen-presenters that ends in homeostasis is replicated by what happens to operatus APCs that ends instead in autoimmune syndromes (Fig. 1).

Polymorphism of FCGR3A gene in sarcoidosis

We showed increased level of immune complexes (ICs) with mycobacterial heat shock proteins (Mtb-hsp) and increased expression of receptors for Fc fragment of immunoglobulin G (FcγR) I-III on blood monocytes with their increased phagocytic activity, responsible for clearance of these ICs in sarcoidosis (SA). Since FcγRIIIa is the most crucial in this process, we genotyped 77 SA patients and 143 healthy controls with polymerase chain reaction for V158F polymorphism of FCGR3A gene, encoding FcγRIIIa. We revealed significantly higher percentage of 158F and 158FF and lower of 158FV variants in Stage I of SA versus controls. Conversely, in Stage II of SA, we found increase in 158VV homozygotes versus controls. We also showed significant increase of 158F and 158FF variants in Stage I vs II and of 158V in Stage II vs I. Therefore, in Stage I, 158F allele may cause decreased FcγRIIIa affinity and clearance of ICs, whereas in Stage II, 158V allele may cause effective FcγRIIIa affinity to ICs with e.g. mycobacteria, their phagocytosis, Mtb-hsp secretion with ICs formation, Mtb-hsp epitope spread and subsequent immune reaction. Thus, V158F polymorphism of FCGR3A may explain the immunocomplexemia in our patients and might serve as prognostic marker of clinical course of sarcoidosis.