Regulation of CD8 Expression in Mast Cells by Exogenous or Endogenous Nitric Oxide

Abstract

We recently reported a novel CD8 molecule on rat alveolar macrophages and peritoneal mast cells (PMC). However, little is known about the regulation of CD8 expression and function on these cells. We investigated the regulation of CD8 expression on PMC by NO, because NO can regulate inflammatory responses and also because anti-CD8 Ab stimulates inducible NO synthase and NO production by PMC and alveolar macrophages. Ligation of CD8α on PMC with Ab (OX8) induced CD8α mRNA expression after 3–6 h, and flow cytometry demonstrated that OX8 treatment increased CD8α protein expression compared with PMC treated with isotype control IgG1. To test whether NO mediates the up-regulation of CD8α, we used the NO donor S-nitrosoglutathione (500 μM) and NO synthase inhibitors (NG-monomethyl-l-arginine and NG-nitro-l-arginine methyl ester; 100 μM). S-nitrosoglutathione up-regulated both mRNA and protein expression of CD8α in PMC compared with that in sham-treated cells, while NO synthase inhibitors down-regulated OX8 Ab-induced CD8α expression. To investigate how NO regulates CD8 expression on PMC, we examined the cGMP-dependent pathway using 8-bromo-cGMP (2 mM) and the guanylate cyclase inhibitor, 1H-oxadiazoloquinoxalin-1-one (20 μM). 8-Bromo-cGMP up-regulated CD8 expression, whereas 1H-oxadiazoloquinoxalin-1-one down-regulated its expression. Thus, ligation of CD8 up-regulates CD8 expression on PMC, a response mediated at least in part by NO through a cGMP-dependent pathway. The significance of this up-regulation of CD8α on mast cells (MC) is unclear, but since ligation of CD8 on MC with OX8 Ab can alter gene expression and mediator secretion, up-regulation of CD8 may enhance the MC response to natural ligation of this novel form of CD8.

Inhibition of Calpain Is a Component of Nitric Oxide-Induced Down-Regulation of Human Mast Cell Adhesion

“…This observation added to existing evidence that NO is an important regulator of MC activity, modulating cell survival, mediator secretion, and gene expression (11)(12)(13)(14)(15). The ability of NO to act as a potent down-regulator of multiple MC functions suggests that it is impinging upon one or more crucial signaling pathways in the cell.…”

Nitric oxide: a major determinant of mast cell phenotype and function

“…Further studies have demonstrated NO increases the expression of CD8, after the ligation of existing CD8 with a specific antibody, in a cGMP-dependent manner (Nohara et al 2001).…”

“…NO can regulate autocrine apoptotic signals (Kitajima et al 1994), and alter surface molecule expression, namely CD8 (Nohara et al 2001). It is apparent that NO is important in both allergic and non-allergic functions of MC.…”

Spotlights on immunological effects of reactive nitrogen species: When inflammation says nitric oxide

“…Moreover, NO has been shown to promote CD8α up-regulation trough NOcGMP pathway in rat peritoneal MCs. This remarkable event enlarges CD8 receptor sensitivity to alternative signals and coincidently boosts MCmediated immune responses [92] . It is well known that during activation processes, MCs adhere to the extracellular matrix basically interacting with fibronectin, vitronectin, collagen type Ⅰ, collagen type Ⅳ, and laminin.…”