Cytokine modulation of liver annexin 1 expression during experimental endotoxemia.

Annexin 1 (ANXA1) is a calcium-binding protein endowed with anti-inflammatory properties. Using an extra-hepatic system, we showed that interleukin (IL)-6 regulates ANXA1 expression at the transcriptional level. The purpose of this study was to determine whether ANXA1 synthesis was modulated by IL-6 during experimental inflammation. We have compared liver ANXA1 expression during systemic and localized inflammatory reaction, using lipopolysaccharide (LPS) and turpentine. LPS treatment strongly induced ANXA1 expression in the liver of wild-type (WT) animals (+600%) whereas a modest increase (+60%) was measured in IL-6 knockout (KO) animals. Turpentine treatment did not affect the expression of ANXA1 in either animal type. LPS enhanced serum corticosteroid levels equally in WT and IL-6 KO mice, whereas higher tumor necrosis factor (TNF)-alpha and IL-1beta levels were released in IL-6 KO animals. Injection of mouse recombinant IL-6 to IL-6 KO animals before LPS or TNF-alpha challenge, replenished ANXA1 liver synthesis to that of WT animals. Exogenous ANXA1 but not ANXA5, administered to IL-6 KO mice before LPS challenge inhibited TNF-alpha release. We propose that ANXA1 acts as a novel acute phase protein, which is controlled in the liver by TNF-alpha and IL-6, and which may contribute to the resolution of systemic endotoxemia through a negative feedback on TNF-alpha release.

NO-mesalamine protects colonic epithelial cells against apoptotic damage induced by proinflammatory cytokines.

The activation of a self-amplifying cascade of caspases, of which caspase-8 is the apical protease, mediates Fas-, tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-, and TNF-alpha-induced apoptosis in colon cell lines. Nitric oxide (NO) protects from apoptosis induced by Fas and TNF-alpha. We examined whether NCX-456, an NO-releasing derivative of mesalamine, protects colon epithelial cells from cytokine-induced apoptosis. Caco-2 and HT-29 cell lines express death factor receptors and are driven to apoptosis in response to incubation with Fas-agonistic antibody, TNF-alpha/interferon-gamma, and TRAIL. The two novel observations reported here are that 1) cotreatment of cells with NCX-456, but not mesalamine, resulted in concentration-dependent protection against death factor-induced apoptosis and inhibition of caspase activity, and 2) exposure to dithiothreitol, an agent that effectively removes NO from thiol groups, resulted in a 70% recovery of caspase activity, which is consistent with S-nitrosation as a major mechanism for caspase inactivation. These data suggest that caspase S-nitrosation represents a mechanism for protection of colonic mucosal epithelial cells from death factor-induced death.

Role of resident peritoneal macrophages and mast cells in chemokine production and neutrophil migration in acute inflammation: evidence for an inhibitory loop involving endogenous IL-10.

The roles played by resident macrophages (Mphi) and mast cells (MCs) in polymorphonuclear leukocyte (PMN) accumulation and chemokine production within the mouse peritoneal cavity in response to administration of zymosan (0.2 and 1 mg), LPS (1 mg/kg), and thioglycolate (0.5 ml of a 3% suspension) were investigated. A marked reduction (>95%) in intact MC numbers was obtained by pretreatment with the MC activator compound 48/80, whereas resident Mphi were greatly diminished (>85%) by a 3-day treatment with liposomes encapsulating the cytotoxic drug dichloromethylene-bisphosphonate. No modulation of thioglycolate-induced inflammation was seen with either pretreatment. Removal of either MCs or Mphi attenuated LPS-induced PMN extravasation without affecting the levels of the chemokines murine monocyte chemoattractant protein-1 and KC measured in the lavage fluids. In contrast, MC depletion inhibited PMN accumulation and murine monocyte chemoattractant protein-1 and KC production in the zymosan peritonitis model. Removal of Mphi augmented the accumulation of PMN elicited by the latter stimulus. This was due to an inhibitory action of Mphi-derived IL-10 because there was 1) a time-dependent release of IL-10 in the zymosan exudates; 2) a reduction in IL-10 levels following Mphi, but not MC, depletion; and 3) an increased PMN influx and chemokine production in IL-10 knockout mice. In conclusion, we propose a stimulus-dependent role of resident MCs in chemokine production and the existence of a regulatory loop between endogenous IL-10 and the chemokine-mediated cellular component of acute inflammation.

Role of inducible nitric oxide synthase in the regulation of neutrophil migration in zymosan-induced inflammation.

In the present study, by comparing the responses in wild-type mice and mice lacking the inducible (or type 2) nitric oxide synthase (iNOS), we investigated the role played by iNOS in the regulation of polymorphonuclear granulocyte (PMN) accumulation and chemokine production in the mouse peritoneal cavity in response to administration of zymosan (0.2 mg). Zymosan injection induced the production of nitric oxide, and triggered a time-dependent PMN immigration into the peritoneal cavity. This response was associated with increases in the level of the chemokines macrophage inflammatory protein (MIP)-1alpha, MIP-2, monocyte chemo-attractant protein (MCP)-1 and cytokine-induced neutrophil chemo-attractant (KC), as measured in the peritoneal cavities. Injection of zymosan also induced a time-dependent increase in the production of the anti-inflammatory cytokine interleukin-10 (IL-10) in the peritoneal cavity. When comparing the response between wild-type and iNOS knockout (KO) mice, we observed that the low-level PMN accumulation measured at 1 hr was slightly but significantly increased in the absence of functional iNOS. On the other hand, the delayed response (2-4 hr after zymosan) of PMN accumulation was suppressed in the iNOS KO mice. The early enhancement of PMN infiltration in the iNOS-deficient mice was associated with increased peritoneal levels of MIP-2, KC and IL-10 proteins. The delayed suppression of PMN infiltration was associated with reduced MIP-2 and IL-10 levels in the peritoneal cavity. The lack of iNOS did not affect the release of MIP-1alpha and MCP-1 at any of the time-points studied. The current data demonstrate that iNOS regulates the production of certain CXC (but not CC) proinflammatory chemokines, the production of IL-10 and exerts a biphasic regulatory effect on PMN accumulation in zymosan-induced acute inflammation.