Inhibition of inducible nitric oxide-synthase (iNOS) enzymatic activity during cutaneous wound repair leads to severely impaired tissue regeneration. To assess whether disturbed leukocyte in filtration might participate in impaired repair, we determined expressional kinetics of neutrophil-attracting macrophage inflammatory protein-2 (MIP-2), and monocyte-attracting macrophage chemoattractant protein-1 (MCP-1) using an excisional wound healing model in mice. MCP-1 was induced in epithelial keratinocytes upon wounding, and our data indicate that NO serves a negative regulatory role for MCP-1 expression in vivo as clearly reduced numbers of wound margin keratinocytes associated with NO-deficient repair compensate for high MCP-1 expression levels observed during normal healing. MIP-2 expression was restricted to hair follicles which were not reduced in number during NO-deficient repair. In vitro studies confirmed a regulatory role of NO for keratinocyte-derived chemokine expression, as NO attenuated IL-1 beta-and TNF-alpha-induced MCP-1 mRNA expression, whereas NO augmented IL-1 beta-induced IL-8 (functional human homolog to murine MIP-2) mRNA expression in the human keratinocyte cell line HaCaT,