Abstractsrc-related cytoplasmic PTKs are physically and functionally associated with cell surface receptors and are involved in signal transduction. In this paper we report the identification of src-related proteins p5Fn, ~~60'" and ~62~" in human microvascular endothelial cells cultured from normal human skin and their physical association with the thrombospondin receptor CD36. Such an association represents a potential signalling pathway by which thrombospondin may regulate angiogenesis.

Nitric oxide is a potent mediator of endothelium-dependent vasodilation, the synthesis of which is catalyzed by the constitutively expressed enzyme endothelial nitric oxide synthase. In this study we have investigated whether human dermal microvascular endothelial cells express endothelial oxide synthase and whether the vasodilator neuropeptides, calcitonin gene-related peptide and substance P, stimulate the release of nitric oxide from these cells. Endothelial nitric oxide synthase was identified by immunohistochemistry in the blood vessels in both the papillary and deep dermis of normal skin, and also in monolayers of human dermal microvascular extracts prepared from both the dermis of normal human skin and human dermal microvascular endothelial cells, a 135-kDa band corresponding to endothelial nitric oxide synthase was identified. Nitric oxide was released from unstimulated human dermal microvascular endothelial cells as assessed by inhibition of platelet aggregation and nitrate formation. Endothelial cell-mediated inhibition of platelet aggregation was blocked by hemoglobin. Calcitonin gene-related peptide, (100 pM to 100 nM) directly inhibited platelet aggregation, and this direct effect was not modulated by microvascular endothelial cells. Substance P (10 nM to 1 muM) and calcitonin gene-related peptide (100 pM to 10 nM) significantly (p<0.05) increased nitrite formation, and this increase was blocked by the competitive nitric oxide synthase antagonist, NG-monomethyl-L-arginine. These results demonstrate that endothelial nitric oxide synthase is expressed in the microvascular endothelium of normal human skin and that human dermal microvascular endothelial cells release nitric oxide constitutively and in response to vasodilator neuropeptides.

Evidence indicates that the neurotrophin nerve growth factor (NGF) is a mediator of cutaneous inflammatory responses. Cellular responses to NGF are facilitated by two receptors called trk A and p75 neurotrophin receptor (p75NTR). In the current study we have investigated the expression of these receptors in lesional and non-lesional skin from patients with plaque psoriasis and in normal skin exposed to three times the minimal erythema dose of ultraviolet (UV) B radiation. Trk A immunostaining was confined to the basal keratinocytes in normal skin. There was a significant reduction in trk A immunostaining in both non-lesional and lesional psoriatic skin compared with control skin. In UVB-irradiated normal skin, there was a significant reduction in trk A immunostaining at 4 h after irradiation, which was still evident at 48 h. In normal skin, p75NTR immunopositive fine nerve fibres were present throughout the dermis and occasionally seen in the epidermis. Thick nerve fibres were evident in the deep dermis and in the middle region of the dermis. p75NTR immunopositive basal keratinocytes were occasionally seen. There was a statistically significant loss of p75NTR immunopositive fine nerve fibres in the epidermis of lesional psoriatic skin and a statistically significant loss of p75NTR immunopositive fine nerve fibres in the dermis in both non-lesional and lesional psoriatic skin. p75NTR immunopositive thick nerve fibres were reduced in lesional psoriatic skin compared with normal skin. UVB irradiation of normal skin led to a statistically significant decrease in the p75NTR immunopositive fine nerve fibres in the epidermis at 48 h after irradiation. There was no significant reduction in the dermal p75NTR immunoreactivity. These results demonstrated that expression of both NGF receptors is decreased following an acute inflammatory stimulus and also in association with a chronic inflammatory dermatosis.

To determine whether the clinical, immunological and serological features of patients with silica-associated systemic sclerosis are different from patients with the 'idiopathic' form of systemic sclerosis (SS) we studied 22 underground coal miners who were exposed to silica dust (SD), 30 mine workers who later developed silicosis (S) and 17 mine workers exposed to silica dust who subsequently developed a systemic sclerosis-like disease (SA-SS). The patients with SA-SS had features clinically indistinguishable from individual patients with SS. They all had Raynaud's phenomenon, 14 had cutaneous sclerosis identical to that seen in acrosclerosis and three had a generalized cutaneous sclerosis. Sixteen patients had bibasilar pulmonary fibrosis, 10 had necrosis of the fingertip pulps, nine had oesophageal involvement and only one patient had renal involvement. Antinuclear antibodies and circulating immune complexes were detected in three and eight patients with SD, 14 and five patients with S and in 16 and nine patients with SA-SS, respectively. Anti-Scl-70 antibody was detected in eight of the 17 patients with SA-SS. Evidence for in vivo endothelial cell damage, as determined by elevated levels of von Willebrand factor, was found in nine patients with SD, 14 patients with S and in 10 patients with SA-SS. Following incubation of the patient's serum with confluent cultures of human umbilical vein endothelial cells there was only a significant reduction in calcium ionophore-induced release of prostacyclin with the serum from SA-SS patients compared to that with control serum (NC). The mean +/- SEM release of 6-keto-PGF1 alpha (the stable metabolite of prostacyclin expressed as ng/10(4) cells) decreased from 2.90 +/- 0.27 to 2.01 +/- 0.33 (SD), 3.34 +/- 0.42 to 1.76 +/- 0.31 (S), 1.98 +/- 0.12 to 0.64 +/- 0.07 (SA-SS) and 2.28 +/- 0.33 to 1.36 +/- 0.21 (NC) with 1 and 20% serum, respectively. This study demonstrates that immune complex and antinuclear antibody formation and in vivo endothelial cell damage occurs following occupational exposure to silica. The patients who subsequently develop a systemic sclerosis-like disease have clinical, immunological and serological features which are indistinguishable from the idiopathic form of the disease although as a group the SA-SS patients have a higher prevalence of pulmonary involvement and the anti-Scl-70 antibody.

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