HSP60 and Anti-HSP60 Antibodies in Vasculitis: They are Two of a Kind

Pathogenic Autoimmunity in Atherosclerosis Evolves from HSP60-Reactive CD4 + T Cells

Clinical evidence suggests anti-Hsp60 antibodies could contribute to atherosclerosis (AS) development, with unclear mechanisms. This study aims to explore the role of anti-HSP60-mediated autoimmunity in AS progression. HSP60-MHC tetramers were used to characterize HSP60-specific CD4 + T cells and assess TCR responses in mice. These cells were transplanted into AS mice to examine immune cell differentiation and infiltration in plaques and blood. Mice were injected with recombinant HSP60 or anti-HSP60 sera to evaluate effects on plaque progression and macrophage activity. Experiments with muMT-/-Apoe-/- mice examined humoral immunity's role in this autoimmunity. HSP60-reactive CD4 + T cells in AS mice differentiated into follicular helper cells, not Th1/Th17. Anti-HSP60 treatments increased macrophage infiltration and M1 polarization, indicating an anti-HSP60-driven inflammatory progression, dependent on humoral immunity. Anti-HSP60 influences macrophage infiltration, polarization, and plaque formation via humoral immunity, shedding light on its potential role in AS progression.

Molecular Chaperonin HSP60: Current Understanding and Future Prospects

Molecular chaperones are highly conserved across evolution and play a crucial role in preserving protein homeostasis. The 60 kDa heat shock protein (HSP60), also referred to as chaperonin 60 (Cpn60), resides within mitochondria and is involved in maintaining the organelle's proteome integrity and homeostasis. The HSP60 family, encompassing Cpn60, plays diverse roles in cellular processes, including protein folding, cell signaling, and managing high-temperature stress. In prokaryotes, HSP60 is well understood as a GroEL/GroES complex, which forms a double-ring cavity and aids in protein folding. In eukaryotes, HSP60 is implicated in numerous biological functions, like facilitating the folding of native proteins and influencing disease and development processes. Notably, research highlights its critical involvement in sustaining oxidative stress and preserving mitochondrial integrity. HSP60 perturbation results in the loss of the mitochondria integrity and activates apoptosis. Currently, numerous clinical investigations are in progress to explore targeting HSP60 both in vivo and in vitro across various disease models. These studies aim to enhance our comprehension of disease mechanisms and potentially harness HSP60 as a therapeutic target for various conditions, including cancer, inflammatory disorders, and neurodegenerative diseases. This review delves into the diverse functions of HSP60 in regulating proteo-homeostasis, oxidative stress, ROS, apoptosis, and its implications in diseases like cancer and neurodegeneration.

Alarmins in autoimmune diseases

Alarmins are endogenous, constitutively expressed, chemotacting and immune activating proteins or peptides released because of non-programmed cell death (i.e. infections, trauma, etc). They are considered endogenous damage-associated molecular patterns (DAMPs), able to induce a sterile inflammation. In the last years, several studies highlighted a possible role of different alarmins in the pathogenesis of various autoimmune and immune-mediated diseases. We reviewed the relevant literature about this topic, for about 160 articles. Particularly, we focused on systemic autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, idiopathic inflammatory myopathies, ANCA-associated vasculitides, Behçet's disease) and cutaneous organ-specific autoimmune diseases (vitiligo, psoriasis, alopecia, pemphigo). Finally, we discussed about future perspectives and potential therapeutic implications of alarmins in autoimmune diseases. In fact, identification of receptors and downstream signal transducers of alarmins may lead to the identification of antagonistic inhibitors and agonists, with the capacity to modulate alarmins-related pathways and potential therapeutic applicability.

HSP60 regulates the cigarette smoke-induced activation of TLR4-NF-κB-MyD88 signalling pathway and NLRP3 inflammasome

Chronic obstructive pulmonary disease (COPD) is characterized by increased cellular stress and inflammation. Heat shock protein 60 (HSP60) is a highly conserved stress protein that acts as a cellular "danger" signal for immune reactions. In this study, we investigated the role of HSP60 in COPD and explored the underlying mechanisms. Expression levels of HSP60 in patients with acute exacerbation of COPD (AECOPD), stable COPD, and healthy people were detected by Western blotting and enzyme-linked immunosorbent assay (ELISA). Moreover, the effect and molecular mechanism of HSP60 in COPD were studied in cigarette smoke (CS)-treated C57BL/6 mice and macrophages. The results showed significant upregulation of HSP60 expression in the peripheral blood mononuclear cells (PBMCs) and sera of patients with AECOPD compared to those with stable COPD or healthy people. CS induced the expression of HSP60 in the COPD mouse model, accelerated the activation of toll-like receptor 4 (TLR4) and NLR family pyrin domain containing 3 (NLRP3) signalling pathways, promoted the increase of inflammatory cells in alveolar lavage fluid and serum inflammatory factors, and induced destruction of lung tissue structure. Furthermore, HSP60 knockdown affected TLR4 and MyD88 expression, IκBα degradation, and nuclear localization of NF-κB and NLRP3 inflammasome activity. Our study revealed that CS stimulates the expression of HSP60, activating the TLR4-MyD88-NF-κB signalling pathway and the NLRP3 inflammasome.

HSP60 in cancer: a promising biomarker for diagnosis and a potentially useful target for treatment

Heat shock proteins (HSPs), most of which are molecular chaperones, are highly conserved proteins produced by cells under physiological stress or pathological conditions. HSP60 (57-69 kDa) can promote or inhibit cell apoptosis through different mechanisms, and its abnormal expression is also related to tumour cell metastasis and drug resistance. In recent years, HSP60 has received increasing attention in the field of cancer research due to its potential as a diagnostic and prognostic biomarker or therapeutic target. However, in different types of cancer, the specific mechanisms of abnormally expressed HSP60 in tumour carcinogenesis and drug resistance are complicated and still require further study. In this article, we comprehensively review the regulative mechanisms of HSP60 on apoptosis, its applications as a cancer diagnostic biomarker and a therapeutic target, evidence of involvement in tumour resistance and the applications of exosomal HSP60 in liquid biopsy. By evaluating the current findings of HSP60 in cancer research, we highlight some core issues that need to be addressed for the use of HSP60 as a diagnostic or prognostic biomarker and therapeutic target in certain types of cancer.

Intense immunostaining of heat shock protein 70 within renal interstitium associates with long-term renal survival in an ANCA-associated vasculitis cohort

In anti-neutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV) genetic predisposition, ANCA autoantibodies, neutrophil extracellular traps (NETs), complement activation, and toll-like receptor signaling are implicated in AAV pathogenesis. Heat shock proteins (HSPs), a highly conserved group of small-sized molecular chaperones, take part in protein folding during cellular stress. Although HSPs were initially observed intracellularly, it has been shown that they can be secreted in the extracellular space and modulate the immune response in various autoimmune diseases including AAV. The scope of the present study is to investigate the role of heat shock protein 60 (HSP60) and 70 (HSP70) in the long renal effects in an ANCA vasculitis cohort. In this cohort of ANCA-associated vasculitis, 29 patients were followed up over 20 years. At diagnosis, immunohistochemistry was performed for HSP60 and HSP70 within the various nephron compartments. Higher renal HSP60 expression was associated with increased interstitial inflammatory infiltrates at diagnosis, while HSP70 expression was associated with a greater extent of interstitial fibrosis at diagnosis. Notably, intense tissue expression of HSP70 at the time of biopsy was associated with a worsened kidney survival. Renal HSP70 expression was associated with poor renal outcomes during long-term follow-up. This finding may indicate a role of HSPs in renal disease progression in ANCA vasculitis. Further validating studies are needed to verify a causative association between HSP70 expression and renal outcomes in ANCA-associated vasculitis.

Immunohistochemistry of Human Hsp60 in Health and Disease: From Autoimmunity to Cancer

Hsp60 (also called Cpn60) is a chaperonin with essential functions for cell physiology and survival. Additionally, its involvement in the pathogenesis of a variety of diseases (e.g., some autoimmune disorders and cancer) is becoming evident with new research. For example, the distribution and levels of Hsp60 in cells and tissues have been found altered in many pathologic conditions, and the significance of these alterations is being investigated in a number of laboratories. The aim of this ongoing research is to determine the meaning of these Hsp60 alterations with regard to pathogenetic mechanisms, diagnosis, classification of lesions, and assessing prognosis and response to treatment.Hsp60 occurs in the mitochondria, i.e., its typical residence according to classic knowledge, and also in other locales, such as the cytosol, the cell membrane, the intercellular space, and biological fluids (e.g., blood and cerebrospinal fluid). Detection and quantitative determinations in all these locations are becoming essential components of laboratory pathology in clinics and research. Consequently, immunohistochemistry targeting Hsp60 is also becoming essential for pathologists and researchers interested in disorders involving this chaperonin.In this chapter, we summarize some recent discoveries on the participation of Hsp60 in the pathogenesis of human diseases, and describe in detail how to perform immunohistochemical reactions for detecting the chaperonin, determining its location, and measuring its quantitative levels.

Hsp60 chaperonopathies and chaperonotherapy: targets and agents

INTRODUCTION

Hsp60 (Cpn60) assembles into a tetradecamer that interacts with the co-chaperonin Hsp10 (Cpn10) to assist client polypeptides to fold, but it also has other roles, including participation in pathogenic mechanisms.

AREA COVERED

Hsp60 chaperonopathies are pathological conditions, inherited or acquired, in which the chaperone plays a determinant etiologic-pathogenic role. These diseases justify selection of Hsp60 as a target for developing agents that interfere with its pathogenic effects. We provide information on how to proceed.

EXPERT OPINION

The information available encourages the development of ways to improve Hsp60 activity (positive chaperonotherapy) when deficient or to block it (negative chaperonotherapy) when pathogenic. Many questions are still unanswered and obstacles are obvious. More information is needed to establish when and why autologous Hsp60 becomes a pathogenic autoantigen, or induces cytokine formation and inflammation, or favors carcinogenesis. Clarification of these points will take considerable time. However, analysis of the Hsp60 molecule and a search for active compounds aimed at structural sites that will affect its functioning should continue without interruption. No doubt that some of these compounds will offer therapeutic hopes and will also be instrumental for dissecting structure-function relationships at the biochemical and biological (using animal models and cultured cells) levels.

Vasculitic neuropathy

Vasculitis is a primary phenomenon in autoimmune diseases such as polyarteritis nodosa, Wegener's granulomatosis, Churg-Strauss syndrome, microscopic polyangiitis, and essential mixed cryoglobulinemia. As a secondary feature vasculitis may complicate, for example, connective tissue diseases, infections, malignancies, and diabetes. Vasculitic neuropathy is a consequence of destruction of the vessel wall and occlusion of the vessel lumen of small epineurial arteries. Sometimes patients present with nonsystemic vasculitic neuropathy, i.e., vasculitis limited to peripheral nerves and muscles with no evidence of further systemic involvement. Treatment with corticosteroids, sometimes in combination with other immunosuppressants, is required to control the inflammatory process and prevent further ischemic nerve damage.

Changes in immunohistochemical levels and subcellular localization after therapy and correlation and colocalization with CD68 suggest a pathogenetic role of Hsp60 in ulcerative colitis

In an earlier work, the role of heat shock protein (Hsp60) in the pathogenesis of ulcerative colitis (UC) was suggested by its significant increase in the pathological mucosa parallel with an increase in inflammatory cells. More data in this direction are reported in this work. We analyzed by immunohistochemistry biopsies of colon tissue from 2 groups of patients with UC and treated with either 5-aminosalicylic acid (5-ASA) alone or in combination with a probiotic. We looked for inflammatory markers and Hsp60. Both the treatments were effective in reducing symptoms but the group treated with both 5-ASA and probiotics showed better clinical results. Amelioration of symptoms was associated with reduction of both inflammation and Hsp60, a reduction that was most marked in the group treated with 5-ASA and probiotics. The levels of Hsp60 positively correlated with those of CD68-positive cells, and double immunofluorescence showed a high index of colocalization of the chaperonin and CD68 in lamina propria. Immunoelectron microscopy showed that Hsp60-classically a mitochondrial protein-was abundantly also present in cytosol in biopsies taken at the time of diagnosis, but not after the treatment. Our data suggest that Hsp60 is an active player in pathogenesis of UC and it can be hypothesized that the chaperonin is responsible, at least in part, for initiation and maintenance of disease.

The ambiguity in immunology

In the present article, we discuss the various ambiguous aspects of the immune system that render this complex biological network so highly flexible and able to defend the host from different external invaders. This ambiguity stems mainly from the property of the immune system to be both protective and harmful. Immunity cannot be fully protective without producing a certain degree of damage (immunopathology) to the host. The balance between protection and tissue damage is, therefore, critical for the establishment of immune homeostasis and protection. In this review, we will consider as ambiguous, various immunological tactics including: (a) the opposing functions driving immune responses, immune-regulation, and contra-regulation, as well as (b) the phenomenon of chronic immune activation as a result of a continuous cross-presentation of apoptotic T cells by dendritic cells. All these plans participate principally to maintain a state of chronic low-level inflammation during persisting infections, and ultimately to favor the species survival.

Multiple sclerosis: a chronic infective cerebrospinal venulitis?

The aetiology proposed for the development of chronic cerebrospinal venous insufficiency (CCSVI) associated with multiple sclerosis (MS) has been the presence of congenital truncular venous malformations. However, this hypothesis is not consistent with the epidemiology or geographical incidence of MS and is not consistent with many of the ultrasonographic or radiographical findings of the venous disturbances found in MS patients. However, the probability of a venous aetiology of MS remains strong based on evidence accumulated from the time the disorder was first described. The method used in this review was to search PubMed for all past medical publications related to vascular, venous, haematological, epidemiological, biochemical, and genetic investigations and treatments of MS. Epidemiological and geographical findings of prevalence of MS indicate the involvement of an infective agent. This review of the venous pathology associated with MS describes a hypothesis that the pathogenesis of the venous disease could be initiated by a respiratory infective agent such as Chlamydophila pneumonia, which causes a specific chronic persistent venulitis affecting the cerebrospinal venous system. Secondary spread of the agent would initially be via the lymphatic system to specifically involve the azygos, internal jugular and vertebral veins. The hypothesis proposes mechanisms by which an infective venous vasculitis could result in the specific neural damage, metabolic, immunological and vascular effects observed in MS. The hypothesis described is consistent with many of the known facts of MS pathogenesis and therefore provides a framework for further research into a venous aetiology for the disease. If MS does result from a chronic infective venulitis rather than a syndrome involving congenital truncular venous malformations, then additional therapies to the currently used angioplasties will be required to optimize results.

Autoantibodies to endothelial cell surface ATP synthase, the endogenous receptor for hsp60, might play a pathogenic role in vasculatides

BACKGROUND

Heat shock protein (hsp) 60 that provides "danger signal" binds to the surface of resting endothelial cells (EC) but its receptor has not yet been characterized. In mitochondria, hsp60 specifically associates with adenosine triphosphate (ATP) synthase. We therefore examined the possible interaction between hsp60 and ATP synthase on EC surface.

METHODOLOGY/PRINCIPAL FINDINGS

Using Far Western blot approach, co-immunoprecipitation studies and surface plasmon resonance analyses, we demonstrated that hsp60 binds to the β-subunit of ATP synthase. As a cell surface-expressed molecule, ATP synthase is potentially targeted by anti-EC-antibodies (AECAs) found in the sera of patients suffering vasculitides. Based on enzyme-linked immunosorbent assay and Western blotting techniques with F1-ATP synthase as substrate, we established the presence of anti-ATP synthase antibodies at higher frequency in patients with primary vasculitides (group I) compared with secondary vasculitides (group II). Anti-ATP synthase reactivity from group I patients was restricted to the β-subunit of ATP synthase, whereas those from group II was directed to the α-, β- and γ-subunits. Cell surface ATP synthase regulates intracellular pH (pHi). In low extracellular pH medium, we detected abnormal decreased of EC pHi in the presence of anti-ATP synthase antibodies, irrespective of their fine reactivities. Interestingly, soluble hsp60 abrogated the anti-ATP synthase-induced pHi down-regulation.

CONCLUSIONS/SIGNIFICANCE

Our results indicate that ATP synthase is targeted by AECAs on the surface of EC that induce intracellular acidification. Such pathogenic effect in vasculitides can be modulated by hsp60 binding on ATP synthase which preserves ATP synthase activity.

Immunohistochemistry of human Hsp60 in health and disease: from autoimmunity to cancer

Hsp60 (also called Cpn60) is a chaperonin with essential functions for cell physiology and survival. Additionally, its involvement in the pathogenesis of a number of diseases (e.g., some autoimmune disorders and cancer) is becoming evident with new research. For example, the distribution and levels of Hsp60 in cells and tissues have been found altered in many pathologic conditions, and the significance of these alterations is being investigated in a number of laboratories. The aim of this ongoing research is to determine the meaning of these Hsp60 alterations with regard to pathogenetic mechanisms, diagnosis, classification of lesions, and assessing of prognosis and response to treatment. Hsp60 occurs in the mitochondria, i.e., its typical residence according to classic knowledge, and also in other locales, such as the cytosol, the cell membrane, the intercellular space, and biological fluids (e.g., blood and cerebrospinal fluid). Detection and quantitative determinations in all these locations are becoming essential components of laboratory pathology in clinics and research. Consequently, immunohistochemistry targeting Hsp60 is also becoming essential for pathologists and researchers interested in disorders involving this chaperonin. In this chapter, we briefly summarize some recent discoveries on the participation of Hsp60 in the pathogenesis of human diseases and describe in detail how to perform immunohistochemical reactions for detecting the chaperonin, determining its location, and measuring its levels of expression.

Chlamydia trachomatis infection and anti-Hsp60 immunity: the two sides of the coin

Chlamydia trachomatis (CT) infection is one of the most common causes of reproductive tract diseases and infertility. CT-Hsp60 is synthesized during infection and is released in the bloodstream. As a consequence, immune cells will produce anti-CT-Hsp60 antibodies. Hsp60, a ubiquitous and evolutionarily conserved chaperonin, is normally sequestered inside the cell, particularly into mitochondria. However, upon cell stress, as well as during carcinogenesis, the chaperonin becomes exposed on the cell surface (sf-Hsp60) and/or is secreted from cells into the extracellular space and circulation. Reports in the literature on circulating Hsp and anti-Hsp antibodies are in many cases short on details about Hsp60 concentrations, and about the specificity spectra of the antibodies, their titers, and their true, direct, pathogenetic effects. Thus, more studies are still needed to obtain a definitive picture on these matters. Nevertheless, the information already available indicates that the concurrence of persistent CT infection and appearance of sf-Hsp60 can promote an autoimmune aggression towards stressed cells and the development of diseases such as autoimmune arthritis, multiple sclerosis, atherosclerosis, vasculitis, diabetes, and thyroiditis, among others. At the same time, immunocomplexes composed of anti-CT-Hsp60 antibodies and circulating Hsp60 (both CT and human) may form deposits in several anatomical locations, e.g., at the glomerular basal membrane. The opposite side of the coin is that pre-tumor and tumor cells with sf-Hsp60 can be destroyed with participation of the anti-Hsp60 antibody, thus stopping cancer progression before it is even noticed by the patient or physician.