Mast cells as a source and target for nitric oxide

Mast cells (MC), which are tissue-resident cells found widely distributed i n the body, are derived from primitive hematopoietic cells. MC produce a va riety of biologically active substances such as histamine, proteases, lipid derivatives and numerous cytokines and chemokines in response to immunolog ic or non-immunologic stimuli. Of interest, it has been reported that roden t MC can also be a source of nitric oxide (NO) derivatives, that they synth esize spontaneously, or only after activation, depending on their subtype. This synthesis appears to be under the control of the expression of the ind ucible isoform of the nitric oxide synthase (iNOS) and of the constitutive neuronal NOS (nNOS). MC might thus be able to influence the survival and fu nctions of other types of NO-sensitive cells in close vicinity. Apart from being a source of NO, MC can also be the target for NO and its derivatives. Indeed, survival and reactivity of rodent MC is influenced by NO derivativ es produced by MC themselves or by other cellular elements in close contact with the MC in tissues. By contrast, the existence of such mechanisms of c ross-talk between MC and NO remains poorly documented in humans. If evidenc e are supplied in favor of such relationship, pharmacological modulation by agents acting at the level of the NO pathway might be of interest in order to regulate the functions of MC in immunologic, neoplastic, inflammatory a nd other conditions. (C) 2001 Elsevier Science B.V. All rights reserved.