Regulation of leukocyte adhesion to heart by the tripeptides feG and feG(NH2)

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Abstract
The role of the D-isomeric form of the salivary gland tripeptide FEG (feG) and its carboxyl-amidated derivative, feG(NH2), in regulating leukocyte adherence to nonfixed atrial slices from Sprague-Dawley rats was examined under static conditions. Optimal binding of the leukocytes was seen if the leukocytes were treated with platelet activating factor (PAF; 10-9M). The increased adherence of PAF-treated peripheral blood leukocytes was totally inhibited by both feG and feG(NH2) (10-9M), as well as by antibodies against CD18 and CD49d. In contrast, the binding of peritoneal leukocytes was blocked only by CD49d antibody. Circulating leukocytes obtained from lipopolysaccharide (LPS) treated (2 mg/kg ip) rats did not bind to atrial slices obtained from normal hearts, but readily bound to atrial slices obtained from LPS-treated rats. This leukocyte binding was inhibited by in vivo feG treatment (100 µg/kg ip, 24 h before harvest) or by treating the isolated cells with feG (10-9M). The amidated peptide feG(NH2) reduced neutrophil accumulation in the atrium elicited by ip injection of LPS, whereas feG was ineffective. The reduction in neutrophil infiltration into the myocardium by feG(NH2) and the prevention of leukocyte interaction with myocytes seen with both feG and feG(NH2) probably results in hindered leukocyte migration in the inflamed heart, resulting in less tissue damage. The inhibition by these tripeptides on neutrophil adhesion to myocytes suggests that salivary glands hormones regulate the severity of cardiac inflammation.Key words: endotoxemia, inflammation, salivary glands, leukocytes, heart, adhesion.