Proteomic and transcriptomic investigation of acne vulgaris microcystic and papular lesions: Insights in the understanding of its pathophysiology.

BACKGROUND: The pathogenesis of acne vulgaris involves several phases including androgen-dependent hyper-seborrhea, colonization by Propionibacterium acnes, and inflammation. Recent investigations have shown that in fact P. acnes provokes the activation of the inflammasome present in macrophages and dendritic cells. This signaling pathway leads to excessive production of interleukin IL-1ß, a proinflammatory cytokine. Nevertheless, these well-studied phenomena in acne fail to elucidate the mechanisms responsible for the appearance of different lesions. METHODS: We investigate response pathways for specific acne lesions such as microcysts and papules using shot-gun proteomic followed by systemic biology and transcriptomic approaches. RESULTS: Results show that most of the proteins identified as differentially expressed between the normal and acne tissue biopsies associated with the immune system response were identified as highly or exclusively expressed in the papule biopsies. They were also expressed in microcysts, but in lower amounts compared to those in papules. These results are supported by the identification of CAMP factor protein produced by P. acnes in microcysts, indicating its enhanced proliferation in this type of lesion CONCLUSIONS: As CAMP factor protein was not detected in papule biopsies, we can see a clear delineation in the stages of progression of acne pathogenesis, which begins with a hyphenated inflammatory response in the papule stage, followed by imbalance of lipid production, which in turn triggers the enhanced proliferation of P. acnes. GENERAL SIGNIFICANCE: We demonstrate that expression inflammation varies across the two types of lesions, suggesting different pathways enhanced as a function of the progression of P. acnes.

Elastin Modification by 4-Hydroxynonenal in Hairless Mice Exposed to UV-A. Role in Photoaging and Actinic Elastosis.

Chronic exposure to ultraviolet (UV) radiation causes oxidative stress, which is involved in photoaging and actinic elastosis. UV and reactive oxygen species generate lipid peroxidation products, including the α, ß-unsaturated carbonyl compounds such as acrolein or 4-hydroxynonenal (4-HNE). These aldehydes can modify proteins of the extracellular matrix, but their role in the pathogenesis of photoaging is not clarified. The aim of this study was to investigate whether these aldehydes contribute to alter elastin metabolism and whether topical carbonyl scavengers delay UV-induced skin photoaging. Hairless mice (4-6-week old) daily exposed to UV-A (20 J cm(-2) per day, up to 600 J cm(-2)) exhibited the typical features of photoaging, associated with a significant increase in 4-HNE- and acrolein-adduct content, and elastotic material deposition. Immunofluorescence studies showed the accumulation of 4-HNE adducts on elastin in the dermis of UV-A-exposed mice. This was mimicked in vitro by incubating orcein-elastin with 4-HNE or acrolein, which altered its digestion by leukocyte-elastase, a feature possibly involved in the accumulation of elastotic material. A daily topical application of carnosine completely reversed the development of photoaging alterations and 4-HNE-adduct formation on elastin. These data emphasize the role of 4-HNE and acrolein in the mechanism of photoaging, and the preventive effect of carbonyl scavengers.

Platelet ERK2 activation by thrombin is dependent on calcium and conventional protein kinases C but not Raf-1 or B-Raf.

Extracellular signal-regulated kinase (ERK) activation pathways have been well characterized in a number of cell types but very few data are available for platelets. The thrombin-induced signaling pathway leading to ERK2 activation in platelets is largely uncharacterized. In this study, we investigated the kinases involved in thrombin-induced ERK2 activation in conditions of maximal ERK2 activation. We found that thrombin-induced mitogen-activated protein kinase/ERK kinase (MEK)1/2 activation was necessary for ERK2 phosphorylation. We obtained strong evidence that conventional protein kinase Cs (PKCs) and calcium are involved in thrombin-induced ERK2 activation. First, ERK2 and MEK1/2 phosphorylation was totally inhibited by low concentrations (1 microM) of RO318425, a specific inhibitor of conventional PKCs. Second, Ca(2+), from either intracellular pools or the extracellular medium, was necessary for ERK2 activation and conventional PKC activation, excluding the involvement of a new class of calcium-insensitive PKCs. Third, LY294002 and wortmannin had no significant effect on ERK2 activation, even at concentrations that inhibit phosphatidylinositol (PI)3-kinase (5 microM to 25 microM and 50 nM, respectively). This suggests that PI3-kinase was not necessary for ERK2 activation and therefore, that PI3-kinase-dependent atypical PKCs were not involved. Surprisingly, in contrast to proliferative cells, we found that the serine/threonine kinases Raf-1 and B-Raf were not an intermediate kinase between conventional PKCs and MEK1/2. After immunoprecipitation of Raf-1 and B-Raf, the basal glutathione S-transferase-MEK1 phosphorylation observed in resting platelets was not upregulated by thrombin and was still observed in the absence of anti-Raf-1 or anti-B-Raf antibodies. In these conditions, the in vitro cascade kinase assay did not detect any MEK activity. Thus in platelets, thrombin-induced ERK2 activation is activated by conventional PKCs independently of Raf-1 and B-Raf activation.

Protease-activated receptor 1 antagonists prevent platelet aggregation and adhesion without affecting thrombin time.

The aim of this study was to investigate the in vitro antithrombotic effects of two PAR1 antagonists, ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation and on the thrombin time in human and guinea-pig platelets. ER121958 inhibited SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 1.73nM and 2.91nM, respectively and SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 2.74nM and 11.9nM, respectively. Similarly, SCH203099 exhibited a non competitive profile of inhibition on both SFLLR-induced guinea-pig and human platelet adhesion with the IC(50) values of 93nM and 127nM, respectively or SFLLR-induced guinea-pig and human platelet aggregation with the IC(50) values of 1.74microM and 2.36microM, respectively. These two antagonists failed to prolong the thrombin time. Altogether, these results highlighted the potent anti-platelets properties of both ER121958 and SCH203099 in an in vitro model of aggregation as well as in a static model of adhesion without any effect on the last step of coagulation cascade. Moreover, this work emphasized that guinea-pig is a suitable animal model to study the role of PAR1 antagonists since the magnitude of the effects of ER121958 and SCH203099 on both SFLLR-induced platelet adhesion and aggregation were similar in both species.

Antithrombotic activity of F 16618, a new PAR1 antagonist evaluated in extracorporeal arterio-venous shunt in the rat.

The purpose of the present work was the evaluation of the antithrombotic activity of a new PAR1 antagonist, F 16618 in arterio-venous shunt in the rat. Arterial thrombosis was induced by insertion of a silk thread (thrombogenic substrate) into an extracorporeal shunt. F 16618 was administered either by intravenous route (0.63-2.5mg/kg) or by oral route (20-80mg/kg). Oral activity of F 16618 was compared to that of aspirin (20-80mg/kg) and clopidogrel (0.63-10mg/kg). Finally, F 16618 was associated to aspirin and/or clopidogrel to test for possible antithrombotic activity and its effects on bleeding time. SFLLR-induced human platelet aggregation was evaluated in the presence of F 16618, demonstrating the anti-aggregant activity of this compound. F 16618 (1.25mg/kg) significantly delayed the time leading to occlusion by 52+/-17%, without affecting bleeding time and in absence of hemodynamic effects. F 16618 given orally dose-dependently increased the time to occlusion. The maximal effect was observed at 40mg/kg (984+/-95s versus 644+/-17s in vehicle group). Aspirin and clopidogrel also dose-dependently lengthened time to occlusion, but this effect was associated with an increase of bleeding time. F 16618 (20mg/kg) orally associated with either aspirin (40mg/kg) or with clopidogrel (1.25mg/kg) potentiated the antithrombotic effects of both compounds without further increasing of bleeding time. In conclusion, F 16618 exerted a potent antithrombotic activity by intravenous and oral routes, without affecting bleeding time. Furthermore, the antithrombotic activity was potentiated when combined with aspirin or clopidogrel.

Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo.

Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.