P-selectin expression in canine cutaneous inflammatory diseases and mast cell tumors

Expression of E- and P-selectin in Tumor Necrosis Factor—induced Dermatitis in Dogs

Adhesion molecules on endothelial cells play an important role in leukocyte recruitment in several inflammatory processes. Vascular selectins mediate the initial adhesion of leukocytes to the blood vessel wall during their extravasation into inflamed tissues, and in vitro studies in dogs have shown that selectin expression can be induced by cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). The objective of this study was to determine whether vascular selectins are induced by cytokines in vivo in a cutaneous model of inflammation in dogs. Skin biopsies were collected from nine dogs at various time points after an intradermal injection of TNF-α (10 ng/site) or phosphate-buffered saline containing 0.1% bovine serum albumin, and immunohistochemistry was performed using anti-P-selectin (MD3) and anti-E-selectin (CL37) monoclonal antibodies. In all animals, TNF-α induced an inflammatory reaction that was maximal at 12 hours and then decreased by 24 and 48 hours. Control skin displayed no expression of E- and P-selectin, whereas TNF-α induced the expression of P-selectin and E-selectin on dermal vessels that was highest at 12 hours and 3 hours, respectively ( P < 0.05). Numerous platelet aggregates recognized by the anti-P-selectin antibody were present in the lumina of vessels and in perivascular tissues. These results demonstrate that TNF-α can induce the expression of P- and E-selectin in vivo in dog skin and suggest that these selectins are involved in leukocyte recruitment in canine dermatitis.

Evaluation of the expression of P-selectin, ICAM-1, and TNF-alpha in bacteria-free lesional skin of atopic dogs with low-to-mild inflammation

Canine atopic dermatitis (AD) is a pruritic skin condition that shares many clinical and pathophysiological features with its human counterpart. A major therapeutic challenge of AD is the control of the skin inflammatory process. A detailed knowledge of the pro-inflammatory molecules involved in cell recruitment in AD would allow for a better control of the disease. We thus have studied the protein expression of P-selectin, ICAM-1 and TNF-alpha in the lesional and non-lesional skin of atopic dogs that had been treated for bacterial infections. Despite a low-to-mild inflammatory process, P-selectin protein was clearly upregulated in the lesional skin areas when compared with non-lesional skin (four-fold average increase). This P-selectin upregulation was accompanied by signs of functional changes such as increased cell margination, and membrane-associated protein expression. Although the expression of ICAM-1 and TNF-alpha was not enhanced in the lesional versus the non-lesional skin, there was a trend towards a correlated upregulation of both molecules. Further studies will help elucidate the significance of the substantial overexpression of P-selectin in canine AD, in particular in a scenario where bacterial antigens are not contributing as pro-inflammatory stimuli.

Mastocitoma cutâneo canino: estudo de 45 casos

Quarenta e cinco mastocitomas cutâneos caninos foram graduados histologicamente com o uso de hematoxilina-eosina. Foram empregados os métodos azul de toluidina e região organizadora nucleolar argirofílica (AgNOR) para, respectivamente, evidenciar os grânulos citoplasmáticos e avaliar o índice de proliferação celular. Diversas características histológicas foram observadas, como distribuição das células na pele, tamanho, forma, aspecto de citoplasma e núcleo, quantidade de estroma, presença de eosinófilos e alterações associadas. Com base nessas caracteríscas, 37,8% dos mastocitomas foram classificados como grau I, 51,1% como grau II e 11,1% como grau III. A média geral de AgNOR nos mastocitomas foi de 1,9 (1,2 a 4,3) e as médias para os graus I, II e III foram, respectivamente, de 1,5, 1,85 e 3,25. A técnica de AgNOR mostrou ser de fácil execução, custo acessível e confiável como meio auxiliar para estimar um prognóstico mais objetivo para os mastocitomas.

Cell adhesion molecules, leukocyte trafficking, and strategies to reduce leukocyte infiltration

Leukocyte-endothelial cell interactions are mediated by various cell adhesion molecules. These interactions are important for leukocyte extravasation and trafficking in all domestic animal species. An initial slowing of leukocytes on the vascular endothelium is mediated by selectins. This event is followed by (1) activation of beta2 integrins after leukocyte exposure to cytokines and pro-inflammatory mediators, (2) adherence of leukocyte beta2 integrins to vascular endothelial ligands (eg, intercellular adhesion molecule-1 [ICAM-1]), (3) extravasation of leukocytes into tissues through tight junctions of endothelial cells mediated by platelet and endothelial cell adhesion molecule-1 (PECAM-1), and (4) perivascular migration through the extracellular matrix via beta1 integrins. Inhibiting excessive leukocyte egress and subsequent free radical-mediated damage caused by leukocyte components may attenuate or eliminate tissue damage. Several methods have been used to modify leukocyte infiltration in various animal models. These methods include nonspecific inhibition of pro-inflammatory mediators and adhesion molecules by nonsteroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids, inhibition of cytokines and cytokine receptors, and inhibition of specific types of cell adhesion molecules, with inhibitors such as peptides and antibodies to beta2 integrins, and inhibitors of selectins, ICAMs, and vascular cell adhesion molecule-1 (VCAM-1). By understanding the cellular and molecular events in leukocyte-endothelial cell interactions, therapeutic strategies are being developed in several animal models and diseases in domestic animal species. Such therapies may have clinical benefit in the future to overcome tissue damage induced by excessive leukocyte infiltration.