Comparison of expression of heat-shock protein 60, Toll-like receptors 2 and 4, and T-cell receptor gammadelta in plaque and guttate psoriasis

Psoriasis and extra domain A fibronectin loops

We have previously postulated that as well as T-helper (Th) 1 and Th17 cells, the transforming growth factor (TGF)-beta/fibronectin (FN)/alpha5beta1 pathway is central to psoriasis pathogenesis. EDA+ FN refers to an alternatively spliced isoform of FN with an additional domain known as extra domain A. EDA+ FN has two important properties pertinent to psoriasis lesions: it stimulates keratinocyte hyperproliferation, and, through stimulation of Toll-like receptor (TLR) 4, stimulates production of proinflammatory cytokines. EDA+ FN production induced by TGF-beta stimulation can be maintained in psoriasis lesions via two main feedback loops. Firstly, EDA+ FN stimulates proliferation of keratinocytes, which, in an autocrine fashion, will release more EDA+ FN. Secondly, EDA+ FN stimulates TLR4 expressed by antigen-presenting cells resulting in the production of proinflammatory cytokines such as tumour necrosis factor-alpha, interleukin (IL)-1, IL-6 and IL-12. The resultant promotion of cutaneous inflammation results in the recruitment of Th1 cells, which also produce EDA+ FN. We propose that these 'FN loops' contribute to the maintenance and progression of psoriatic lesions. Finally, although the association between psoriasis and heart/thrombotic disease remains unclear one plausible link may be the promotion of atherosclerosis and thrombotic heart disease by EDA+ FN.

The role of toll-like receptors in host defenses and their relevance to dermatologic diseases

The family of toll-like receptors (TLRs) plays a central role in the cutaneous immune defense system. To date, different TLRs have been found on several major cell populations of the skin, such as keratinocytes, fibroblasts, antigen-presenting cells, and melanocytes. Activation of TLRs leads, via different intracellular signaling pathways, to the production of pro-inflammatory stimuli, and is considered a danger signal that should transform the skin in to the functional state of defense. However, TLRs have also been implicated in tissue homeostasis and renewal. Within the group of TLRs, two types have been identified: surface-expressed TLRs, which are predominantly active against bacterial cell wall compounds; and intracellular receptors, which preferentially recognize virus-associated pattern molecules. In addition, surface-expressed receptors trigger phagocytotic and maturation signals, while the intracellular TLRs lead to the induction of antiviral genes. Our review aims to outline the importance of TLRs in the pathogenesis of numerous skin diseases and the potential of TLR agonists as a treatment option for various skin diseases.

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.

Role of corticotropin-releasing hormone and receptor in the pathogenesis of psoriasis

Psoriasis is a chronic inflammatory disease characterized by epidermal keratinocytic hyperproliferation and abnormal differentiation. It is one of the most illustrative examples of the close relation between exacerbation of disease and the psychopathologic burden of the patients. However, the mechanism remains poorly understood. In recent years, evidence has suggested that endocrine stress responses not only are under control of the central nervous system but also occur in peripheral tissue, outside of the classical HPA axis. Corticotrophin-releasing hormone (CRH) is a central component of the hypothalamic-pituitary-adrenal (HPA) axis and is an important coordinator of the systemic stress response. In peripheral sites, cutaneous CRH and CRH-receptor1 (CRH-R1) is believed to regulate various functions of the skin that are important for local homeostasis. These findings have shed new light on the role of peripheral CRH and CRH-R1 in cutaneous diseases, especially psoriasis. Many researchers focus on the pro-inflammatory role of CRH, such as CRH-induced activation of mast cells in the phenomenon of stress related exacerbation of cutaneous inflammatory diseases, and some researches demonstrated that CRH protein expression was increased in the affected skin of psoriasis. Meanwhile, it is reported that CRH could downregulate pro-inflammatory factors, such as IL-18. Tagen found CRH-R1 mRNA expression in psoriasis skin lower than that in normal controls. Previous studies revealed that the functional role of the CRH/CRH-R1 system in pathological human skin conditions remains to be identified. Interestingly, we found that both CRH and CRH-R1 were presented in psoriatic lesion, perilesional skin and normal control skin by immunohistochemistry, and lesions from patients with psoriasis showed significantly lower CRH/CRH-R1 expression compared with psoriatic perilesional skin and normal control skin. Presumably a localized circuit regulates the peripheral functions of cutaneous CRH/CRH-R1, and the aberrant expression of CRH/CRH-R1 in the skin disturbs the local homeostasis and leads to abnormal differentiation and proliferation in keratinocytes. However, dysfunction of keratinocytes may decrease CRH/CRH-R1 expression because of disharmony in differentiation and proliferation of keratinocytes. Thus, we hypothesize that a cutaneous CRH/CRH-R1 system might be aberrant in lesions of psoriasis. The detuning of CRH/CRH-R1 regulation might contribute to the formation of plaque in psoriasis. What is more important, we hypothesize that the role of CRH/CRH-R1 system might play a protective role in the pathogenesis of psoriasis. This would provide a new treatment for psoriasis. Thus, further study in vitro and in vivo has to be done to test our hypothesis.

A comprehensive review of biomarkers in psoriasis

Psoriasis is a common, chronic skin disorder, the pathogenesis of which is incompletely understood. Results from various clinical and experimental studies indicate that psoriasis is a complex, multifactorial disease with a genetic predisposition. Factors such as climate, physical trauma, drug, stress and infections (Streptococcus, human immunodeficiency virus) are known to trigger psoriasis. The success of treatment of psoriasis with T-cell depletion and antitumour necrosis factor (TNF)-alpha treatment is explained by the involvement of T cells and TNF- alpha in the pathogenesis of psoriasis. The biochemical basis for the pathogenesis of psoriasis can be attributed to both overexpression and underexpression of certain proteins in psoriatic lesions. The anomalies in protein expression can be classified as abnormal keratinocyte differentiation, keratinocyte hyperproliferation and inflammation. Oxidative stress (OS) and increased free-radical generation have been linked to skin inflammation in psoriasis. The review presents evidence for various markers of psoriasis that can be targeted for effective treatment, including biomarkers of inflammation, keratinocyte hyperproliferation and abnormal differentiation, and stress.

Hepatosplenic T-cell lymphomas and therapy with TNF-alpha-blocking biologics: a risk for psoriasis patients?

Tumor necrosis factor (TNF)-alpha antagonists have considerably improved the therapeutic approach to chronic inflammatory disorders including psoriasis vulgaris. Recently, some cases of highly aggressive hepatosplenic T-cell lymphoma (HSTCL) have developed in patients with inflammatory bowel diseases (IBD) being treated with infliximab or adalimumab. Analysis of the published data suggests that the emergence of HSTCL is favored by the combination of purine analogues and infliximab or adalimumab in the therapy of a granulomatous inflammation involving Vdelta1(+)gammadelta T cells. Because psoriasis vulgaris is different from IBD in regard to the type of inflammation, the concomitant therapies used and the tissue-specific subsets of gammadelta T cells, the use of infliximab or adalimumab in psoriasis may not necessarily be associated with an increase in the risk of HSTCL.

Heat-shock proteins can promote as well as regulate autoimmunity

Heat-shock proteins (Hsps) are among the most highly conserved and immunogenic proteins shared by microbial agents and mammals. Under physiological conditions, the ubiquitously distributed Hsps maintain the integrity and function of other cellular proteins when cells are exposed to stressful stimuli. However, owing to their conserved nature and stress inducibility, Hsps may become targets of immune response. The T cells and/or antibodies induced by a microbial Hsp may crossreact with the corresponding mammalian Hsp (molecular mimicry) and trigger an autoimmune response, which if unchecked can lead to immune pathology and clinical manifestations. Furthermore, enhanced expression of Hsp under stress can unveil previously hidden antigenic determinants that can initiate and perpetuate autoimmune reactivity. Also, the innate immune mechanisms activated by an Hsp can reinforce and even direct the type of adaptive immune response to that protein. Hsps have been implicated in the induction and propagation of autoimmunity in several diseases, including rheumatoid arthritis, atherosclerosis and type 1 diabetes. However, Hsps possess immunoregulatory attributes as well and therefore, are being exploited for immunomodulation of various immune-mediated disorders.

Toll-like receptors in skin

TLRs have emerged as a major class of PRRs that are involved in detecting invading pathogens in the skin and initiating cutaneous immune responses. TLRs are expressed on many different cell types in the skin, including keratinocytes and Langerhans cells in the epidermis. Each TLR can recognize a different microbial component and there are differences among the TLR signaling pathways, which lead to distinct immune responses against a given pathogen. Certain TLRs have been implicated in the pathogenesis of skin diseases, such as atopic dermatitis, psoriasis, and acne vulgaris. In addition, TLRs have been shown to be important in cutaneous host defense mechanisms against common bacterial, fungal, and viral pathogens in the skin, such as S aureus, C albicans, and HSV. Since the discovery that topical TLR agonists promote antiviral and antitumor immune responses, there has been considerable interest in the development of TLR-based therapies for skin diseases, skin cancer, and infections. Future research involving TLRs in skin will hopefully provide new insights into host defense against skin pathogens and novel therapeutic targets aimed at treating skin disease and skin cancer.