Activated, not resting, platelets increase leukocyte rolling in murine skin utilizing a distinct set of adhesion molecules

Step up to the platelet: Role of platelets in inflammation and infection

Platelets are anucleated cells derived from megakaryocytes that are primarily responsible for hemostasis. However, in recent years, these cytoplasts have become increasingly recognized as immune cells, able to detect, interact with, and kill pathogens. As platelets are involved in both immunity and coagulation, they have a central role in immunothrombosis, a physiological process in which immune cells induce the formation of microthrombi to both prevent the spread of pathogens, and to help facilitate clearance. In this review, we will highlight the role of platelets as key players in the inflammatory and innate immune response against bacterial and viral infection, including direct and indirect interactions with pathogens and other immune cells.

Molecular mechanisms of catch bonds and their implications for platelet hemostasis

Adhesive molecular bonds between blood cells are essential for thrombosis and hemostasis as they provide means for platelet adhesion, aggregation, and signaling in flowing blood. According to the nowadays conventional definition, a "catch" bond is a type of non-covalent bio-molecular bridge, whose dissociation lifetime counter-intuitively increases with applied tensile force. Following recent experimental findings, such receptor-ligand protein bonds are vital to the blood cells involved in the prevention of bleeding (hemostatic response) and infection (immunity). In this review, we examine the up-to-date experimental discoveries and theoretical insights about catch bonds between the blood cells, their biomechanical principles at the molecular level, and their role in platelet thrombosis and hemostasis.

Platelet activation: a promoter for psoriasis and its comorbidity, cardiovascular disease

Psoriasis is a chronic inflammatory skin disease with a prevalence of 0.14% to 1.99%. The underlying pathology is mainly driven by the abnormal immune responses including activation of Th1, Th17, Th22 cells and secretion of cytokines. Patients with psoriasis are more likely to develop cardiovascular disease (CVD) which has been well recognized as a comorbidity of psoriasis. As mediators of hemostasis and thromboinflammation, platelets play an important part in CVD. However, less is known about their pathophysiological contribution to psoriasis and psoriasis-associated CVD. A comprehensive understanding of the role of platelet activation in psoriasis might pave the path for more accurate prediction of cardiovascular (CV) risk and provide new strategies for psoriasis management, which alleviates the increased CV burden associated with psoriasis. Here we review the available evidence about the biomarkers and mechanisms of platelet activation in psoriasis and the role of platelet activation in intriguing the common comorbidity, CVD. We further discussed the implications and efficacy of antiplatelet therapies in the treatment of psoriasis and prevention of psoriasis-associated CVD.

Cancer metastasis chemoprevention prevents circulating tumour cells from germination

The war against cancer traces back to the signature event half-a-century ago when the US National Cancer Act was signed into law. The cancer crusade costs trillions with disappointing returns, teasing the possibility of a new breakthrough. Cure for cancer post-metastases still seems tantalisingly out of reach. Once metastasized, cancer-related death is extremely difficult, if not impossible, to be reversed. Here we present cancer pre-metastasis chemoprevention strategy that can prevent circulating tumour cells (CTCs) from initiating metastases safely and effectively, and is disparate from the traditional cancer chemotherapy and cancer chemoprevention. Deep learning of the biology of CTCs and their disseminating organotropism, complexity of their adhesion to endothelial niche reveals that if the adhesion of CTCs to their metastasis niche (the first and the most important part in cancer metastatic cascade) can be pharmaceutically interrupted, the lethal metastatic cascade could be prevented from getting initiated. We analyse the key inflammatory and adhesive factors contributing to CTC adhesion/germination, provide pharmacological fundamentals for abortifacients to intervene CTC adhesion to the distant metastasis sites. The adhesion/inhibition ratio (AIR) is defined for selecting the best cancer metastasis chemopreventive candidates. The successful development of such new therapeutic modalities for cancer metastasis chemoprevention has great potential to revolutionise the current ineffective post-metastasis treatments.

Looking beyond the Skin: Pathophysiology of Cardiovascular Comorbidity in Psoriasis and the Protective Role of Biologics

Psoriasis is a chronic systemic inflammatory disease associated with a higher incidence of cardiovascular disease, especially in patients with moderate to severe psoriasis. It has been estimated that severe psoriasis confers a 25% increase in relative risk of cardiovascular disease, regardless of traditional risk factors. Although the underlying pathogenic mechanisms relating psoriasis to increased cardiovascular risk are not clear, atherosclerosis is emerging as a possible link between skin and vascular affection. The hypothesis that the inflammatory cascade activated in psoriasis contributes to the atherosclerotic process provides the underlying basis to suggest that an anti-inflammatory therapy that improved atherosclerosis would also reduce the risk of MACEs. In this sense, the introduction of biological drugs which specifically target cytokines implicated in the inflammatory cascade have increased the expectations of control over the cardiovascular comorbidity present in psoriasis patients, however, their role in vascular damage processes remains controversial. The aim of this paper is to review the mechanistic link between psoriasis and cardiovascular disease development, as well as analyzing which of the biological treatments could also reduce the cardiovascular risk in these patients, fueling a growing debate on the modification of the general algorithm of treatment.

Comparison of mean platelet volume (MPV) and red blood cell distribution width (RDW) between psoriasis patients and controls: A systematic review and meta-analysis

BACKGROUND

The predictive role of hematological indexes of mean platelet volume (MPV) and red cell distribution width (RDW) has been demonstrated in cardiovascular disease concomitant with psoriasis. This meta-analysis is intended to assess whether MPV and RDW can also serve as biomarkers for the early diagnosis and disease severity assessment of psoriasis.

MATERIAL AND METHODS

13 studies which enrolled 1331 psoriasis patients and 919 healthy volunteers were included after screening the search results from PubMed, Embase and the Cochrane Library since inception to Mar 14, 2020. MPV of psoriasis participants and their counterparts was assessed in 10 studies, and RDW was evaluated in 4 studies, while the disease severity was measured by the Psoriasis Area and Severity Index (PASI) in 11 studies. Random-effect model analysis was applied to calculate pooled standard mean difference (SMD) with 95% confidence interval (95% CI).

RESULTS

Associations of MPV and RDW with the presence of psoriasis were demonstrated (MPV: SMD = 0.503, 95% CI: 0.242-0.765; RDW: SMD = 0.522, 95% CI: 0.228-0.817), but no statistically significant correlation of MPV and disease severity of psoriasis was found in meta-regression analysis (p = 0.208). Subgroup analysis revealed that the diagnosis value of MPV and RDW was consistent regardless of PASI and study type. Heterogeneity analysis between studies was implemented by chi-squared test and I2 statistics. Begg's and Egger's test were utilized for the evaluation of publication bias. The sensitivity analysis revealed no significant alteration no matter which study was excluded.

CONCLUSION

MPV and RDW could serve as promising predictive diagnostic biomarkers of psoriasis.

Platelets: Underestimated Regulators of Autoinflammation in Psoriasis

Platelets have long been known as mediators of hemostasis and, more recently, as mediators of thromboinflammation, although their physiopathological role has mostly been investigated in the context of disease of internal organs, such as liver and kidney, or systemic disorders. Of late, exciting recent data suggest that platelets may also play a role in inflammation at distal sites such as the skin: recent studies show that platelets, by engaging polymorphonuclear neutrophils (PMNs), contribute to local inflammation in the frequent skin disorder, psoriasis. In an experimental model, systemic depletion of platelets drastically attenuated skin inflammation by preventing PMN infiltration of the skin. A broader role of platelets in different types of skin inflammation is therefore likely, and in this paper, we specifically review recent advances in psoriasis. Special emphasis is given to the crosstalk with systemic platelet effects, which may be of interest in psoriasis-related cardiovascular comorbidities. Furthermore, we discuss the potential for platelet-centered interventions in the therapy for psoriasis.

Platelet Dysfunction and Its Role in the Pathogenesis of Psoriasis

BACKGROUND

Psoriasis is an immune-mediated inflammatory skin disease in conjunction with the systemic inflammatory process. It appears to be related to increased risks of cardiovascular disease events, especially in severe cases. The hemostatic balance is disrupted due to the prothrombotic bias in psoriasis, which might be mainly preserved by platelet hyperactivity. Platelets are also immune cells that initiate and regulate immune and inflammatory processes, except as the principal mediator of hemostasis and thrombosis, and platelet dysfunction is deeply involved in the pathogenesis of psoriasis.

SUMMARY

The aim of this study is to perform a review that expounds abnormal platelet function in psoriasis and explains the important role of platelets in the pathogenic mechanism of psoriasis in order to provide new targets for comprehensive medical treatment.

High Levels of Platelet-Lymphocyte Complexes in Patients with Psoriasis Are Associated with a Better Response to Anti-TNF-α Therapy

Psoriasis is currently considered to be an immune-mediated disease whose patho-mechanisms involve platelet activation, which seems to correlate with the activity of the disease. Platelet activation is associated with the formation of platelet-lymphocyte complexes (PLyC), although their significance remains unknown. Moreover, biological treatments that target tumor necrosis factor-α (TNF-α) reduce platelet activation. To clarify the significance of PLyC, we compared their levels in patients with psoriasis with those of healthy donors and determined whether platelet binding modifies the secretion of IL-17A by T helper cells. Finally, we assessed the effect of anti-TNF-α treatment on PLyC in responder and non-responder patients with psoriasis. Ours results demonstrated an increase in PLyC in patients with psoriasis. Moreover, the percentage of IL-17-secreting cells was observed to be higher in the platelet-lymphocyte complex population, and these cells tended to secrete greater amounts of IL-17A. Psoriasis patients treated with anti-TNF-α normalized platelet-lymphocyte complex values, and the basal percentage of platelet-T helper lymphocyte complexes was significantly higher in the responder group. In conclusion, PLyC are increased in psoriasis patients, and the number of complexes decreases in response to anti-TNF-α treatment, specifically in the responder group of patients. This finding suggests that PLyC are a prognostic biomarker of response to anti-TNF-α therapy, but prospective studies are necessary to verify these results in patients with psoriasis.

Platelets Aggregate With Neutrophils and Promote Skin Pathology in Psoriasis

Psoriasis is a frequent systemic inflammatory autoimmune disease characterized primarily by skin lesions with massive infiltration of leukocytes, but frequently also presents with cardiovascular comorbidities. Especially polymorphonuclear neutrophils (PMNs) abundantly infiltrate psoriatic skin but the cues that prompt PMNs to home to the skin are not well-defined. To identify PMN surface receptors that may explain PMN skin homing in psoriasis patients, we screened 332 surface antigens on primary human blood PMNs from healthy donors and psoriasis patients. We identified platelet surface antigens as a defining feature of psoriasis PMNs, due to a significantly increased aggregation of neutrophils and platelets in the blood of psoriasis patients. Similarly, in the imiquimod-induced experimental in vivo mouse model of psoriasis, disease induction promoted PMN-platelet aggregate formation. In psoriasis patients, disease incidence directly correlated with blood platelet counts and platelets were detected in direct contact with PMNs in psoriatic but not healthy skin. Importantly, depletion of circulating platelets in mice in vivo ameliorated disease severity significantly, indicating that both PMNs and platelets may be relevant for psoriasis pathology and disease severity.

Platelets in Skin Autoimmune Diseases

Systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and small vessel vasculitis are three autoimmune diseases frequently manifested in the skin. They share common pathogenic features, including production of autoantibodies, loss of tolerance to self-antigens, tissue necrosis and fibrosis, vasculopathy and activation of the coagulation system. Platelets occupy a central part within the coagulation cascade and are well-recognized for their hemostatic role. However, recent cumulative evidence implicates their additional and multifaceted immunoregulatory functions. Platelets express immune receptors and they store growth factors, cytokines, and chemokines in their granules enabling a significant contribution to inflammation. A plethora of activating triggers such as damage associated molecular patterns (DAMPs) released from damaged endothelial cells, immune complexes, or complement effector molecules can mediate platelet activation. Activated platelets further foster an inflammatory environment and the crosstalk with the endothelium and leukocytes by the release of immunoactive molecules and microparticles. Further insight into the pathogenic implications of platelet activation will pave the way for new therapeutic strategies targeting autoimmune diseases. In this review, we discuss the inflammatory functions of platelets and their mechanistic contribution to the pathophysiology of SSc, ANCA associated small vessel vasculitis and other autoimmune diseases affecting the skin.

Biomarkers of subclinical atherosclerosis in patients with psoriatic arthritis

Background: Psoriatic arthritis (PsA) is a chronic immune-mediated disease. It is associated with an increase in cardiovascular risk factors (obesity, hypertension, diabetes, and dyslipidemia), giving a higher risk of major adverse cardiovascular events. Patients with PsA have an increased incidence of subclinical atherosclerosis and endothelial dysfunction. The aim of this study is to perform a review of the biomarkers of subclinical atherosclerosis in patients with PsA.

Methods: A search was performed in the electronic databases (PubMed, Web of Science, Scopus, and Embase) up until July 2017. Studies were considered if they included data on biomarkers of subclinical atherosclerosis in PsA, and each article was then reviewed for quality and clinical relevance. After completing the literature search, all screened literature was summarized and discussed in our study group (CaRRDs study group).

Results: The initial search produced 532 abstracts, which were limited to 258 potentially relevant articles by preliminary review of the titles and by excluding review articles and case reports (n=274). A further 102 articles were deemed ineligible after examining the abstracts. Full texts of the remaining 156 articles were retrieved. Most articles were excluded because they were not relevant to the biomarkers of subclinical atherosclerosis in psoriasis and/or PsA. In the end, 54 articles were deemed eligible for this review.

Conclusion: Patients with PsA showed more severe atherosclerotic disease compared with patients with only psoriasis. This may have been due to the higher systemic inflammatory burden from the combination of both diseases. In patients with PsA some molecules may be considered as markers of atherosclerotic disease, and their detection may be a prognostic marker, in addition to imaging procedures, for the development of atherosclerotic disease, and could be suitable for the management of patients with PsA.

Platelets are important for the development of immune tolerance: Possible involvement of TGF-β in the mechanism

Platelets have diverse roles in immune processes in addition to their key functions in haemostasis and thrombosis. Some studies imply that platelets may be possibly related to the immune tolerance induction. However, the role of platelets in the development of immune tolerance is not fully understood. The purpose of this study was to investigate the role of platelets in the development of regulatory mechanisms responsible for cutaneous inflammation using a mouse model of low zone tolerance (LZT). Mice were treated with 2,4,6-trinitro-1-chlorobenzene (TNCB) 8 times every other day for tolerance induction with administration of anti-platelet antibody or control antibody during the tolerance induction phase every 3 days. After the treatment for the tolerance induction, mice were sensitized and then challenged with TNCB. The contact hypersensitivity (CHS) was significantly decreased at 24 hours after challenge in the mice with LZT than in those without LZT. Platelet depletion via administration of anti-platelet antibody reversed the inhibition of CHS and reduced the frequency of Foxp3⁺ Tregs in the inflamed skin and draining lymph nodes in mice with LZT. In addition, repeated low-dose skin exposure resulted in elevated plasma levels of transforming growth factor (TGF)-β1. Interestingly, platelet depletion reduced plasma TGF-β1 levels of mice with LZT. Furthermore, the CHS response was reduced by administration of recombinant TGF-β1 during platelet depletion in mice with LZT. Administration of anti-TGF-β antibody reversed the inhibition of the CHS responses. These results suggest that platelets are involved in the induction of immune tolerance via the release of TGF-β1.

Associations between the neutrophil-to-lymphocyte and the platelet-to-lymphocyte ratios and the presence and severity of psoriasis: a systematic review and meta-analysis

The diagnosis of psoriasis, an immune-mediated disease that affects 2% of the population in Western countries, is largely based on history and clinical examination. The aim of this systematic review and meta-analysis was to investigate the associations between the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) and the presence and clinical severity of psoriasis. A systematic literature search was conducted in PubMed, Web of Science, and Scopus, from inception to January 2018. Twelve case-control studies enrolling 1067 psoriasis patients (537 males and 530 females) and 799 healthy controls (404 males and 395 females) were included in the meta-analysis. The NLR was evaluated in all the studies, while the PLR was assessed in four studies. Pooled results showed that both the NLR and the PLR values were significantly higher in patients with psoriasis (SMD = 0.69, 95% CI 0.53-1.85, p < 0.001, and SMD = 0.40, 95% CI 0.12-0.68, p = 0.006, respectively). There were no significant differences in NLR values according to the severity of disease (p = 0.52). The NLR and the PLR are significantly associated with the presence, but not with the severity, of psoriasis. Further studies are required to determine the additional utility of these haematological indexes in the diagnosis of psoriasis.

Systemic Inflammation and Cardiovascular Comorbidity in Psoriasis Patients: Causes and Consequences

Psoriasis is a common inflammatory skin disease characterized by the appearance of red scaly plaques that can affect any part of the body. High prevalence, chronicity, disfiguration, disability, and associated comorbidity make it a challenge for clinicians of multiple specialties. Likewise, its complex pathogenesis, comprising inflammation, hyperproliferation, and angioneogenesis, intrigues numerous scientific disciplines, namely, immunology. From a clinical perspective, the severity of psoriasis is highlighted by its increased mortality, with cardiovascular diseases contributing the highest excess risk. From a scientific point of view, psoriasis has to be considered a systemic inflammatory condition, as blood biomarkers of inflammation are elevated and imaging techniques document sites of inflammation beyond the skin. While the association of psoriasis with cardiovascular diseases is now widely accepted, causes and consequences of this association are controversially discussed. This review comments on epidemiologic, genetic, and mechanistic studies that analyzed the relation between psoriasis and cardiovascular comorbidity. The hypothesis of psoriasis potentially being an independent cardiovascular risk factor, driving atherosclerosis via inflammation-induced endothelial dysfunction, will be discussed. Finally, consequences for the management of psoriasis with the objective to reduce the patients’ excess cardiovascular risk will be pointed out.

Long-term treatment of chronic plaque psoriasis with biological drugs can control platelet activation: targeting the bridge between inflammation and atherothrombosis

Introduction

Platelet activation is elevated in moderate to severe psoriasis, and the reduction in platelet activation during short-term treatment has already been demonstrated. Soluble P-selectin is a well-established marker of platelet activation.

Aim

To show whether the long-term treatment of psoriasis with biological drugs can reduce elevated platelet activation.

Material and methods

An observational study of 27 patients with chronic plaque psoriasis, treated with infliximab, adalimumab, etanercept, or ustekinumab for up to 12 months was conducted. Psoriasis area and severity index (PASI), serum P-selectin and interleukin (IL)-6 were monitored throughout the treatment.

Results

There was no significant correlation between PASI and platelet activation in our patients. After 3 months of treatment, a significant reduction in PASI and IL-6 was found, while P-selectin was not significantly reduced. When a cohort of patients who had shown elevated P-selectin prior to the treatment was evaluated, a significant reduction in P-selectin was observed in all 8 patients following 3 months; a reduction that was sustained after 6 and 12 months of therapy.

Conclusions

We conclude that PASI is not a good predictor of platelet activity in patients with PASI near to 10. Biological drugs reduce platelet activation in patients who have increased platelet activation prior to treatment, and this effect is stable during chronic therapy.

Platelets and Airway Diseases. In: Gresele P, Kleiman NS, Lopez JA, Page CP, editors. Platelets in Thrombotic and Non-Thrombotic Disorders. Cham: Springer International Publishing; 2017. pp. 1149-68. [DOI: 10.1007/978-3-319-47462-5_77]

The role of platelets as inflammatory cells is now well established. Given the peculiar characteristics of the lung circulation, with a broad capillary bed, platelets are especially involved with the physiology of the lungs and play a key role in a number of inflammatory lung disorders. The platelet precursors, megakaryocytes, are detected in the lung microcirculation; moreover platelets with their endothelium-protective and vascular reparative activities contribute to the lung capillary blood barrier integrity. Given the function of the lungs as first wall against pathogen invasion, platelets participate in immune defence of the normal lung. On the other hand, platelets may turn into effectors of the inflammatory reaction of the lungs to allergens, to infectious agents, to chemical agents and may contribute strongly to the perpetuation of chronic inflammatory reactions, largely by their ability to interact with other inflammatory cells and the endothelium. In this chapter we provide an overview of the role of platelets in several inflammatory lung disorders discussing the pathophysiologic bases of platelet involvement in these conditions and the experimental and clinical evidence for a role of platelets in lung diseases.

Increased levels of circulating platelet-derived microparticles in psoriasis: Possible implications for the associated cardiovascular risk

AIM

To evaluate platelet activation markers in psoriasis patients, compared to controls, and investigate their association with the inflammatory burden of psoriasis.

METHODS

Forty psoriatic patients without cardiovascular disease, and 12 healthy controls were subjected to measurement of baseline platelet CD62P, CD63 and CD42b expression, platelet-leukocyte complexes, i.e., platelet-monocyte complexes (PMC), platelet-neutrophil complexes (PNC) and platelet-lymphocyte complexes, and concentrations of platelet-derived microparticles (PMPs) using flow cytometry. Both larger-size (0.5-0.9 μm) and smaller-size (< 0.5 μm) PMPs were determined. Serum interleukin (IL)-12 and IL-17 levels were also measured by enzyme-linked immunosorbent assay. The severity of psoriasis was evaluated by the Psoriasis Area Severity Index (PASI).

RESULTS

PMP concentrations were significantly higher in psoriasis patients than controls [mean ± standard error of mean (SEM): 22 ± 5/μL vs 11 ± 6/μL; P = 0.018), for both smaller-size (10 ± 2/μL vs 4 ± 2/μL; P = 0.033) and larger-size (12 ± 3/μL vs 6 ± 4/μL; P = 0.014) PMPs. Platelet CD62P, CD63 and CD42b expression and circulating PMC and PNC were similar between the two groups. Lower circulating PLC were observed in psoriasis patients compared to controls (mean ± SEM: 16% ± 3% vs 23% ± 6%; P = 0.047). Larger-size PMPs were related with IL-12 levels (P < 0.001) and smaller-size PMPs with both IL-12 and IL-17 levels (P < 0.001). Total PMPs also correlated with IL-12 (P < 0.001). CD63 expression was positively correlated with both IL-12 and IL-17 (P < 0.05). Increased PASI score was associated with increased levels of larger-size PMPs (r = 0.45; P = 0.011) and increased CD63 expression (r = 0.47; P < 0.01).

CONCLUSION

PMPs, known to be predictive of cardiovascular outcomes, are increased in psoriasis patients, and associated with high inflammatory disease burden. Enhanced platelet activation may be the missing link leading to cardiovascular events in psoriatic patients.

Tissue-engineered human psoriatic skin supplemented with cytokines as an in vitro model to study plaque psoriasis

AIM

Psoriasis is a chronic inflammatory skin disease. To study its complex etiology, a psoriatic skin substitute model supplemented with a cytokine cocktail has been used.

MATERIALS & METHODS

Reconstructed psoriatic skin substitutes were supplemented with a cocktail of four cytokines: TNF-α, IL-1α, IL-6 and IL-17A, to monitor their impact on gene expression by DNA microarray.

RESULTS

Gene profiling analyses identified several deregulated genes reported as being also deregulated in psoriasis skin in vivo (S100A12, IL-8, DEFB4A and KYNU). The expression of those genes was dramatically increased compared with basal levels of controls (p < 0.005 to < 0.05).

CONCLUSION

Psoriatic substitutes supplemented with a cocktail of TNF-α, IL-1α, IL-6 and IL-17A showed similar transcriptome alterations to those found in psoriasis.

Platelets Play Differential Role During the Initiation and Progression of Autoimmune Neuroinflammation

RATIONALE

Platelets are known to participate in vascular pathologies; however, their role in neuroinflammatory diseases, such as multiple sclerosis (MS), is unknown. Autoimmune CD4 T cells have been the main focus of studies of MS, although the factors that regulate T-cell differentiation toward pathogenic T helper-1/T helper-17 phenotypes are not completely understood.

OBJECTIVE

We investigated the role of platelets in the modulation of CD4 T-cell functions in patients with MS and in mice with experimental autoimmune encephalitis, an animal model for MS.

METHODS AND RESULTS

We found that early in MS and experimental autoimmune encephalitis, platelets degranulated and produced soluble factors serotonin (5-hydroxytryptamine), platelet factor 4, and platelet-activating factor, which specifically stimulated differentiation of T cells toward pathogenic T helper-1, T helper-17, and interferon-γ/interleukin-17-producing CD4 T cells. At the later stages of MS and experimental autoimmune encephalitis, platelets became exhausted in their ability to produce proinflammatory factors and stimulate CD4 T cells but substantially increased their ability to form aggregates with CD4 T cells. Formation of platelet-CD4 T-cell aggregates involved the interaction of CD62P on activated platelets with adhesion molecule CD166 on activated CD4 T cells, contributing to downmodulation of CD4 T-cell activation, proliferation, and production of interferon-γ. Blocking of formation of platelet-CD4 T-cell aggregates during progression of experimental autoimmune encephalitis substantially enhanced proliferation of CD4 T cells in the central nervous system and the periphery leading to exacerbation of the disease.

CONCLUSION

Our study indicates differential roles for platelets in the regulation of functions of pathogenic CD4 T cells during initiation and progression of central nervous system autoimmune inflammation.

Psoriasis is a systemic disease with multiple cardiovascular and metabolic comorbidities. Dermatol Clin. 2015;33:41-55. [PMID: 25412782 DOI: 10.1016/j.det.2014.09.004]

There is evidence that patients with moderate to severe psoriasis have an increased risk of conditions such as cardiovascular disease, obesity, diabetes mellitus, and metabolic syndrome. The precise mechanisms underlying the observed increase in cardiovascular disease in psoriasis remain to be defined but inflammatory pathways mutual to both conditions are probably involved. Suppression of systemic inflammation in psoriasis could help reduce cardiovascular inflammation but robust evidence is still lacking evidence is lacking. This article summarizes the current literature on cardiovascular and metabolic comorbidities in psoriasis, identifies research gaps, and suggests management strategies to reduce cardiovascular risk in patients with moderate to severe psoriasis.

The role of heparanase in pulmonary cell recruitment in response to an allergic but not non-allergic stimulus

Heparanase is an endo-β-glucuronidase that specifically cleaves heparan sulfate proteoglycans in the extracellular matrix. Expression of this enzyme is increased in several pathological conditions including inflammation. We have investigated the role of heparanase in pulmonary inflammation in the context of allergic and non-allergic pulmonary cell recruitment using heparanase knockout (Hpa^-/-) mice as a model. Following local delivery of LPS or zymosan, no significant difference was found in the recruitment of neutrophils to the lung between Hpa^-/- and wild type (WT) control. Similarly neutrophil recruitment was not inhibited in WT mice treated with a heparanase inhibitor. However, in allergic inflammatory models, Hpa^-/- mice displayed a significantly reduced eosinophil (but not neutrophil) recruitment to the airways and this was also associated with a reduction in allergen-induced bronchial hyperresponsiveness, indicating that heparanase expression is associated with allergic reactions. This was further demonstrated by pharmacological treatment with a heparanase inhibitor in the WT allergic mice. Examination of lung specimens from patients with different severity of chronic obstructive pulmonary disease (COPD) found increased heparanase expression. Thus, it is established that heparanase contributes to allergen-induced eosinophil recruitment to the lung and could provide a novel therapeutic target for the development of anti-inflammatory drugs for the treatment of asthma and other allergic diseases.

Is enhanced platelet activation the missing link leading to increased cardiovascular risk in psoriasis?

BACKGROUND

Psoriasis is an immune mediated inflammatory skin disease associated with systemic inflammation resulting in increased risk for associated cardiovascular co-morbidities. The role of platelet activation in the pathophysiology of this condition has not been clearly studied. We undertook to study the platelet activation markers in psoriasis, as compared to controls and to identify its association with disease severity in psoriasis.

METHODS

Sixty-two patients with psoriasis and 62 age and gender matched healthy controls were enrolled in this cross-sectional study. The severity of the disease was assessed using the psoriasis area severity index (PASI) scoring. The platelet indices [mean platelet volume (MPV) and platelet distribution width (PDW)] were estimated by an automated haematological laser optical analyzer. Plasma soluble P-selectin and platelet derived microparticle (PDMP) concentrations, serum high sensitivity C-reactive protein (hs-CRP) and interleukin (IL)-6 concentrations were estimated in all study participants. Platelet aggregation was assessed using adenosine diphosphate (ADP) as aggregating agent.

RESULTS

We observed that there was significantly higher platelet indices (MPV and PDW) in patients with psoriasis, when compared to controls. Plasma soluble P-selectin concentrations, PDMP and platelet aggregation were significantly elevated in patients with psoriasis, as compared to controls. We also found significantly higher concentrations of hs-CRP and IL-6 in patients with psoriasis, as compared to controls. Platelet activation and systemic inflammation markers correlated positively with PASI, except PDW. We also observed significant positive correlation between platelet activation and systemic inflammation in psoriasis.

CONCLUSION

Significant platelet activation and systemic inflammation were observed in patients with psoriasis, especially when associated with severe disease. The increased platelet activation might be the missing link between the persistent inflammation and the development of atherosclerotic plaque leading onto cardiovascular co-morbidities seen associated with psoriasis.

Aspirin and P2Y12 Inhibitors in platelet-mediated activation of neutrophils and monocytes

Platelets are key players in haemostasis and represent a pivotal link between inflammation, immunity and atherogenesis. Depending on the (patho)physiological environment platelets modulate various leukocyte functions via release of inflammatory mediators and direct cell-cell interactions. Elevated levels of circulating platelet-leukocyte aggregates are found in patients suffering from several thrombotic or inflammatory conditions. Platelet-monocyte and platelet-neutrophil interaction can trigger pro- and anti-inflammatory responses and modulate effector functions of all leukocyte subpopulations. These platelet-mediated immune responses have implications for the progression of cardiovascular diseases and also play a crucial role during infections, cancer, transplantations and other inflammatory diseases of several organs. Antiplatelet therapy including the COX inhibitor aspirin and/or ADP receptor P2Y12 inhibitors such as clopidogrel, prasugrel and ticagrelor are the therapy of choice for various cardiovascular complications. Both aspirin and P2Y12 inhibitors attenuate platelet-leukocyte interactions, thereby also modulating immune responses. This may have beneficial effects in some pathological conditions, while it might be detrimental in others. This review aims to summarise the current knowledge on platelet-leukocyte interactions and the impact of aspirin and P2Y12 inhibition on platelet-mediated immune responses and to give an overview on the effects of antiplatelet therapy on platelet-leukocyte interplay in various diseases.

Platelets and allergic inflammation

Irrefutable clinical evidence demonstrates the activation of platelets in allergic diseases, including asthma, allergic rhinitis, and eczema. Indeed, experimental models of allergic disease have now shown that platelets play a fundamental role in the tissue recruitment of leucocytes following exposure to allergens. Furthermore, the extravascular presence of platelets in lungs of patients with asthma, and in animal models of allergic lung inflammation suggests that platelets may also contribute directly to allergic inflammation, through alterations in lung function, or by modulating processes involved in airway wall remodelling. Despite significant platelet activation in patients with allergic diseases, it is of note that these patients have been described as having a mild haemostastic defect, rather than an increased incidence of thrombosis. This suggests a dichotomy exists in platelet activation during inflammation compared to haemostasis, and that hitherto undiscovered platelet activation pathways might be exploited to create novel anti-inflammatory therapies without affecting the critical function of platelets in haemostasis.

Mechanistic explanation for platelet contribution to cancer metastasis

Cancer-associated mortality is frequently caused by metastasis, however, our understanding of this process remains incomplete and therapeutic options are limited. Metastasis is a dynamic multi-step process involving intravasation of tumor cells into the host's blood and lymphatic vessels, their dissemination within the circulation, and finally arrest and extravasation in a distant organ where they establish secondary tumors. It is generally conceived that platelets contribute to all steps of hematogenous tumor dissemination. In this review, we provide an overview of the current knowledge of the platelet receptors involved in tumor cell-induced platelet aggregation, an essential immune surveillance escape mechanism of circulating tumor cells. We discuss how platelets prevent immunological attack, contribute to tumor cell extravasation and thereby facilitate colonization of distant organs.

Vascular cell adhesion molecule-1 (VCAM-1)--an increasing insight into its role in tumorigenicity and metastasis

Vascular cell adhesion molecule-1 (VCAM-1) first attracted attention more than two decades ago as endothelial adhesion receptor with key function for leukocyte recruitment in term of cellular immune response. The early finding of VCAM-1 binding to melanoma cells, and thus a suggested mechanistic contribution to metastatic spread, was the first and for a long time the only link of VCAM-1 to cancer sciences. In the last few years, hallmarked by a growing insight into the molecular understanding of tumorigenicity and metastasis, an impressive variety of VCAM-1 functionalities in cancer have been elucidated. The present review aims to provide a current overview of VCAM-1 relevance for tumor growth, metastasis, angiogenesis, and related processes. By illustrating the intriguing role of VCAM-1 in cancer disease, VCAM-1 is suggested as a new and up to now underestimated target in cancer treatment and in clinical diagnosis of malignancies.

Atopic dermatitis and risk of ischemic stroke: a nationwide population-based study

BACKGROUND

Epidemiological studies have shown a strong association between systemic inflammatory diseases, particularly allergic diseases, and cardiovascular diseases. However, the relationship between atopic dermatitis (AD) and ischemic stroke remains unclear.

METHOD

The study identified 20,323 AD patients and 20,323 comorbidity-matched subjects between 2005 and 2008. The two cohorts were followed until 31 December 2009. Ischemic stroke and other cardiovascular events were determined.

RESULTS

During the follow-up period, 301 (1.48%) patients in the AD cohort and 228 (1.12%) matched subjects experienced ischemic stroke. After multivariate adjustment, patients with AD had a 1.33-fold (95% confidence interval (CI), 1.12-1.59; P = 0.001) increased incidence of ischemic stroke. Adjusted hazard ratios for the risk of ischemic stroke in patients with mild, moderate, and severe AD were 1.20 (95% CI, 1.00-1.45; P = 0.052), 1.64 (95% CI, 1.23-2.19; P = 0.001), and 1.71 (95% CI, 1.15-2.56; P = 0.008), respectively. The log-rank test showed a higher cumulative incidence of ischemic stroke in the severe AD group than in the moderate and mild AD groups during the follow-up period (P < 0.001).

CONCLUSIONS

AD may be an independent risk factor for ischemic stroke, and risk of ischemic stroke increases with AD severity.

Platelet activation: a link between psoriasis per se and subclinical atherosclerosis--a case-control study

BACKGROUND

Pathomechanisms of both psoriasis and atherosclerosis may involve platelet activation. Activated platelets show increased P-selectin; CD62 expression, and mean platelet volume (MPV). Impaired brachial artery flow-mediated dilatation (FMD) is related to atherosclerosis.

OBJECTIVES

To determine the presence of subclinical atherosclerosis in patients with psoriasis (without overt cardiovascular complications or traditional cardiovascular disease risk factors), compared with controls.

METHODS

In this case-control study, 25 patients with psoriasis and 25 age- and gender-matched healthy individuals were subjected to assessment of MPV, CD62 expression using flow cytometry, and brachial artery FMD and transthoracic echocardiography by cardiac ultrasound scanner.

RESULTS

A statistically highly significant increased CD62 expression, but not MPV, was found in cases compared with controls, and in patients with moderate/severe psoriasis compared with either mild cases or controls (P < 0.001). CD62 expression was statistically significantly positively correlated with the Psoriasis Area and Severity Index (PASI) score (P < 0.001), baseline brachial artery diameter (P = 0.03) but not FMD and aortic root diameter (ARD; P = 0.03). ARD was statistically significantly higher in patients with moderate/severe psoriasis compared with controls (P = 0.017). Stepwise simple linear regression analysis revealed that PASI score was the most important factor affecting CD62 expression (P < 0.001).

CONCLUSIONS

Our study showed increased atherosclerosis risk in patients with psoriasis, particularly those with moderate/severe disease, as evidenced by increased expression of platelet CD62 compared with healthy controls. Moreover, we found a positive correlation between CD62 expression and ARD (another possible marker of atherosclerosis), with positive correlation to the PASI score; the most important factor influencing CD62 expression. However, our data on MPV and FMD do not support the use of either value for diagnosing subclinical atherosclerosis in patients with psoriasis in further studies.

Protective mechanisms of adenosine 5'-monophosphate in platelet activation and thrombus formation

Platelet activation is relevant to a variety of acute thrombotic events. We sought to examine adenosine 5'-monophosphate (AMP) mechanisms of action in preventing platelet activation, thrombus formation and platelet-related inflammatory response. We assessed the effect of AMP on 1) P-selectin expression and GPIIb/IIIa activation by flow cytometry; 2) Platelet aggregation and ATP secretion induced by ADP, collagen, TRAP-6, convulxin and thrombin; 3) Platelet rolling and firm adhesion, and platelet-leukocyte interactions under flow-controlled conditions; and, 4) Platelet cAMP levels, sP-selectin, sCD40L, IL-1β, TGF-β1 and CCL5 release, PDE3A activity and PKA phosphorylation. The effect of AMP on in vivo thrombus formation was also evaluated in a murine model. The AMP docking with respect to A2 adenosine receptor was determined by homology. AMP concentration-dependently (0.1 to 3 mmol/l) inhibited P-selectin expression and GPIIb/IIIa activation, platelet secretion and aggregation induced by ADP, collagen, TRAP-6 and convulxin, and diminished platelet rolling and firm adhesion. Furthermore, AMP induced a marked increase in the rolling speed of leukocytes retained on the platelet surface. At these concentrations AMP significantly decreased inflammatory mediator from platelet, increased intraplatelet cAMP levels and inhibited PDE3A activity. Interestingly, SQ22536, ZM241385 and SCH58261 attenuated the antiplatelet effect of AMP. Docking experiments revealed that AMP had the same orientation that adenosine inside the A2 adenosine receptor binding pocket. These in vitro antithrombotic properties were further supported in an in vivo model of thrombosis. Considering the successful use of combined antiplatelet therapy, AMP may be further developed as a novel antiplatelet agent.

Crossing the endothelial barrier during metastasis

During metastasis, cancer cells disseminate to other parts of the body by entering the bloodstream in a process that is called intravasation. They then extravasate at metastatic sites by attaching to endothelial cells that line blood vessels and crossing the vessel walls of tissues or organs. This Review describes how cancer cells cross the endothelial barrier during extravasation and how different receptors, signalling pathways and circulating cells such as leukocytes and platelets contribute to this process. Identification of the mechanisms that underlie cancer cell extravasation could lead to the development of new therapies to reduce metastasis.

Psoriasis as a systemic disease

Psoriasis is an inflammatory immune-mediated disease that affects the skin and has pathogenic effects with systemic impact. The relationship between psoriasis and comorbidities remains controversial. The hypothesis of a causative role of psoriasis in its cardiovascular and metabolic comorbidities is based on pathophysiologic concepts establishing a link between chronic inflammation in psoriasis, endothelial dysfunction, formation of atherosclerotic plaques, and the different compounds of metabolic syndrome. Psoriasis management has to be multidisciplinary. It implicates identification and treatment of psychological disorders, addictions, and associated cardiovascular and metabolic diseases, together with improvement of quality of life of patients.

Synthetic isoxazole as antiplatelet agent

Abstract Nine synthetic isoxazoles were evaluated as antiplatelet agents and studied the possible mechanism of more active compound. The initial screening was evaluating all compounds against platelet aggregation assays. The most active compound was isoxazole 8 showing an inhibition of platelet aggregation around 70%. In subsequent experiments, ADP and collagen were used as agonists to explore the possible inhibitory mechanisms of isoxazole 8 in platelet aggregation and secretion. We reported the effect of isoxazole 8 for reducing the expression of inflammatory markers, such as soluble CD40 ligand (sCD40L) and soluble P-selectin (sP-selectin), on activated platelets. Of this form, an inhibition of sCD40L and sP-selectin can prevent the onset of an atherosclerotic lesion.

The initial hours of metastasis: the importance of cooperative host-tumor cell interactions during hematogenous dissemination

Tumor cells transit from the primary tumor via the blood circulation to form metastases in distant organs. During this process, tumor cells encounter a number of environmental challenges and stimuli that profoundly impact their metastatic potential. Here, we review the cooperative and dynamic host-tumor cell interactions that support and promote the hematogenous dissemination of cancer cells to sites of distant metastasis. In particular, we discuss what is known about the cross-talk occurring among tumor cells, platelets, leukocytes, and endothelial cells and how these cell-cell interactions are organized both temporally and spatially at sites of extravasation and in the early metastatic niche.

SIGNIFICANCE

Metastasis is a function not only of tumor cells but also involves cooperative interactions of those cells with normal cells of the body, in particular platelets and leukocytes. These other cell types alter the behavior of the tumor cells themselves and of endothelial cells lining the vasculature and assist in tumor cell arrest and extravasation at sites of metastasis and subsequently in the establishment of tumor cells in the early metastatic niche. A better understanding of the important role that these contact and paracrine interactions play during metastasis will offer new opportunities for therapeutic intervention.

Effector CD8 T cell trafficking within the liver

CD8 T cells play a critical role in several pathological conditions affecting the liver, most notably viral hepatitis. Accordingly, understanding the mechanisms that modulate the intrahepatic recruitment of CD8 T cells is of paramount importance. Some of the rules governing the behavior of these cells in the liver have been characterized at the population level, or have been inferred by studying the intrahepatic behavior of other leukocyte subpopulations. In contrast to most microvascular beds where leukocyte adhesion is restricted to the endothelium of post-capillary venules, it is now becoming clear that in the liver leukocytes, including CD8 T cells, can efficiently interact with the endothelium of hepatic capillaries (i.e. the sinusoids). While physical trapping has been proposed to play an important role in leukocyte adhesion to hepatic sinusoids, there is mounting evidence that T cell recruitment to the liver is highly regulated and depends on recruitment signals that are either constitutive or induced by inflammation. We review here several specific adhesive mechanisms that have been shown to regulate CD8 T cell trafficking within the liver, as well as highlight recent data that establish platelets as key cellular regulators of intrahepatic CD8 T cell accumulation.

Cardiovascular mortality in psoriasis and psoriatic arthritis: epidemiology, pathomechanisms, therapeutic implications, and perspectives

Psoriasis and psoriatic arthritis are associated with an increased cardiovascular mortality. Although the underlying pathogenesis is not yet fully understood, it is clear that these seemingly organ-specific disorders cause a systemic inflammatory burden as mirrored by elevated biomarkers in the patients' blood. Emerging evidence points toward insulin resistance and endothelial dysfunction as direct consequences; these in turn drive the process of atherosclerosis. As psoriasis and psoriatic arthritis therefore represent cardiovascular risk factors, they must be taken into account by primary care physicians when defining treatment goals for the comorbidities of the respective patients (e.g., arterial hypertension or dyslipidemia). Secondary and tertiary care physicians need to consider a more comprehensive treatment approach, including aspects of lifestyle intervention. Finally, effective long-term anti-inflammatory, disease-modifying therapy may contribute to reducing patients' cardiovascular risk.

Microvesicles at the crossroads between infection and cardiovascular diseases

Observational and experimental studies continue to support the association of infection and infection-stimulated inflammation with development of cardiovascular disease (CVD) including atherosclerosis and thrombosis. Microvesicles (MV) are heterogeneous populations of sealed membrane-derived vesicles shed into circulation by activated mammalian cells and/or pathogenic microbes that may represent an interface between bacterial/microbial infection and increased risk of CVD. This review evaluates how MV act to modulate and intersect immunological and inflammatory responses to infection with particular attention to progression of CVD. Although infection-related stimuli provoke release of MV from blood and vascular cells, MV express phosphatidylserine and other procoagulant factors on their surface, which initiate and amplify blood coagulation. In addition, MV mediate cell-cell adhesion, which may stimulate production of pro-inflammatory cytokines in vascular cells, which in turn aggravate progression of CVD and propagate atherothrombosis. MV transfer membrane receptors, RNA and proteins among cells, and present auto-antigens from their cells of origin to proximal or remote target cells. Because MV harbor cell surface proteins and contain cytoplasmic components of the parent cell, they mediate biological messages and play a pivotal role in the crossroad between infection-stimulated inflammation and CVDs.

Epidemiology and Potential Pathomechanisms of Cardiovascular Comorbidities in Psoriasis: A Report from the GRAPPA 2010 Annual Meeting

There is increasing awareness that psoriasis is more than “skin deep.” Several recent reviews focused on biomarkers have indicated the systemic dimension of psoriasis and the comorbidity that psoriasis shares with other chronic inflammatory diseases. Of emerging significance is the relationship to cardiovascular disease, which contributes substantially to patients’ increased mortality. This article examines currently available evidence favoring the concept of a causal link between psoriasis and cardiovascular disease, and summarizes a report represented at the 2010 Annual Meeting of GRAPPA (Group for Research and Assessment of Psoriasis and Psoriatic Arthritis).

Mimicking the inflammatory cell adhesion cascade by nucleic acid aptamer programmed cell-cell interactions

Nature has evolved effective cell adhesion mechanisms to deliver inflammatory cells to inflamed tissue; however, many culture-expanded therapeutic cells are incapable of targeting diseased tissues following systemic infusion, which represents a great challenge in cell therapy. Our aim was to develop simple approaches to program cell-cell interactions that would otherwise not exist toward cell targeting and understanding the complex biology of cell-cell interactions. We employed a chemistry approach to engineer P- or L-selectin binding nucleic acid aptamers onto mesenchymal stem cells (MSCs) to enable them to engage inflamed endothelial cells and leukocytes, respectively. We show for the first time that engineered cells with a single artificial adhesion ligand can recapitulate 3 critical cell interactions in the inflammatory cell adhesion cascade under dynamic flow conditions. Aptamer-engineered MSCs adhered on respective selectin surfaces under static conditions >10 times more efficiently than controls including scrambled-DNA modified MSCs. Significantly, engineered MSCs can be directly captured from the flow stream by selectin surfaces or selectin-expressing cells under flow conditions (≤2dyn/cm²). The simple chemistry approach and the versatility of aptamers permit the concept of engineered cell-cell interactions to be generically applicable for targeting cells to diseased tissues and elucidating the biology of cell-cell interactions.

Platelet P-selectin reflects a state of cutaneous inflammation: possible application to monitor treatment efficacy in psoriasis

Haemostasis-maintaining platelets are also recognized as important modulators in the regulation of immune response. Activated platelets expressing P-selectin (CD62P) are involved in the extravasation of leucocytes. This study evaluated platelet P-selectin expression as a biomarker for cutaneous inflammation. P-selectin expression was assessed by flow cytometry in 147 successive patients suffering from an inflammatory or infectious skin condition at the day of admission for in-patient treatment as well as a day prior to demission. Forty-one patients admitted for allergy testing served as controls. A commercially available ELISA was used in 17 patients to determine soluble P-selectin in the plasma. In patients with psoriasis, the Psoriasis Area and Severity Index (PASI) was documented as a measure for disease severity. We observed a significant increase in platelet P-selectin expression in patients with inflammatory or infectious disorders, when compared to the control group (3,01% vs. 1,46%; P < 0.000001). Successful treatment resulted in a significant decrease in P-selectin expression to the level of the control group. In the case of psoriasis (n = 47), we found highly significant correlation between P-selectin and PASI (r = 0.51; P < 0.000001), as well as between the change in the PASI and the change in P-selectin expression (r = 0.4; P = 0.006). Platelet P-selectin expression as determined by flow cytometry correlated well with the results of soluble P-selectin, determined by ELISA (r = 0.63; P < 0.01). Thus, platelet P-selectin expression may be used as an efficacy biomarker to monitor treatment success in psoriasis. As platelet P-selectin correlates with soluble P-selectin in patient plasma, which can be measured by ELISA, the latter is feasible also for routine use.

Systemic therapy of plaque-type psoriasis ameliorates endothelial cell function: results of a prospective longitudinal pilot trial

Severe psoriasis is associated with significant cardiovascular mortality. We therefore investigated the effects of systemic therapy on the cardiovascular risk of psoriasis patients. Thirteen consecutive patients receiving fumaric acid esters were included and followed for 24 weeks both clinically and by means of laboratory monitoring, 10 completed the study. Eight of ten patients showed a PASI-50 response. Two of three patients with clinical insulin resistance (Homeostasis Model Assessment of insulin resistance >2.5) showed normal insulin responsiveness at the end of the study. Clinical improvement was paralleled by a reduction of high-sensitive CRP serum levels (median -25%). There was a trend toward reduced serum levels for the vascular endothelial growth factor (median -10%) and resistin (median -4%), while the potentially cardio-protective adiponectin showed a trend toward increased serum levels under therapy (median +19%). Systemic endothelial function assessed by venous occlusion plethysmography revealed an improvement of endothelial vasodilator function after 24 weeks of treatment (p < 0.02). This is the first prospective study documenting an amelioration of endothelial cell function in patients with moderate-to-severe plaque-type psoriasis under effective continuous systemic therapy. Future studies need to compare the cardioprotective effects of different treatment modalities, based on hard end points such as the rate of myocardial infarction.

Platelet-leukocyte interactions in cardiovascular disease and beyond

Platelet-leukocyte interactions define a basic cell process that is characterized by the exchange of signals between platelets and different types of leukocytes and that bridges 2 fundamental pathophysiological events: atherothrombosis and inflammatory immune reactions. When this process takes place at the site of atherosclerotic plaque development or at the site of endothelial injury, platelet-dependent leukocyte recruitment and activation contributes to the inflammatory reaction of the vessel wall, which accounts for the exacerbation of atherosclerosis and for intimal hyperplasia and plaque instability. Moreover, platelet-leukocyte interactions may have a key role in modulating a wide array of responses of both the innate and adaptive immune systems, thus contributing to the pathogenesis of inflammatory diseases and tissue damage, as well as to host defense.

Psoriasis and cardiovascular disease

Current epidemiological data support the association between psoriasis and cardiovascular (CV) risk, in apparent correlation with psoriasis severity. Although less unanimously, evidence of an increased prevalence of CV diseases among psoriasis patients has been reported, including ischemic heart disease, cerebrovascular, peripheral vascular and heart structural disorders. In particular, various studies showed a correlation between psoriasis and major CV events (i.e., myocardial infarction, stroke), while others investigated subclinical changes of blood vessels, such as intima-media thickness increase, arterial stiffness and coronary artery calcification. A series of different mechanisms, like traditional CV risk or iatrogenic risk factors, inflammation, hemostasis dysregulation, hyperhomocysteinemia, and shared genetic susceptibility, are thought to underlie this epidemiological association. Among these elements, inflammation and its related cytokine milieu, including Th1-mediated response and Th17/Treg imbalance, C reactive protein and the newly implicated osteopontin are considered to play a primary role, even if yet to be fully understood.