Thrombin-induced expression of the KC gene in cultured aortic endothelial cells. Involvement of proteolytic activity and protein kinase C

IL-1 regulates in vivo C—X—C chemokine induction and neutrophil sequestration following endotoxemia

The influx of neutrophils into tissues in response to inflammatory stimuli involves C—X—C chemokines. Interleukin-1 (IL-1) stimulates chemokine production in vitro , but its role in vivo on chemokine production is not as clearly understood. We hypothesized that IL-1 mediates in vivo tissue C—X—C chemokine production induced by systemic lipopolysaccharide (LPS). IL-1 activity was blockedbyIL-1 receptor antagonist (IL-1Ra). Rats were injected with Salmonella typhi LPS (0.5 mg/kg) with and without prior administration of IL-1Ra. Cytokine-induced neutrophil chemoattractant-1 (CINC-1) and macrophage inflammatory protein-2 (MIP-2) protein and mRNA levels, tissue neutrophil accumulation, and indices of organ injury were measured. LPS administration resulted in increased plasma, lung, and liver IL-1β that was decreased by IL-1Ra. LPS also induced an increase in plasma, lung, and liver CINC-1 and MIP-2 protein and mRNA. However, IL-1Ra had no effect on LPS-induced plasma or lung tissue CINC-1 levels. In contrast, IL-1Ra pretreatment did significantly decrease CINC-1 protein expression in the liver (45% decrease) and MIP-2 protein expression in plasma (100% decrease), lung (72% decrease) and liver (100% decrease) compared to LPS-treated controls. Steady-state mRNA levels by Northern blot analysis of both CINC-1 and MIP-2 in lung and liver were similar to the protein findings. Pretreatment with IL-1Ra also resulted in a 47% and 59% decrease in lung and liver neutrophil accumulation, respectively, following LPS. In addition, indices of both lung and liver injury were decreased in animals pretreated with IL-1Ra. In summary, LPS induces IL-1β and MIP-2 expression in the lung and liver, both of which are IL-1 dependent. Although lung neutrophil accumulation in both lung and liver after LPS is also IL-1 mediated, lung CINC-1 levels were unaffected by IL-1Ra. These data suggest that IL-1 regulates tissue chemokine expression and neutrophil accumulation after LPS.

Time-dependent changes in donor brain death related processes

Donor brain death (BD) affects kidney function and survival after transplantation. Studies on brain dead kidney donors indicate that, besides inflammation and coagulation, cytoprotective gene expression is activated as well. Here, we evaluated in a time-course experiment progression of these renal BD-related processes. Animals were sacrificed 0.5, 1, 2 or 4 h after BD and compared to sham-operated controls. Proinflammatory genes (E-selectin, MCP-1, II-6) were massively up-regulated (p < 0.05) already 0.5 h after BD. Inducers of proinflammatory gene expression were either activated (NF-kappaB) or induced in expression (Egr-1) after 0.5 h of BD. Increased numbers of infiltrating granulocytes were seen in the interstitium from 0.5 h on. Also, expression of protective genes HO-1 and HSP70 were increased within 0.5 h. Remarkably, reactive oxygen species formation was detectable only in the later phase of BD. Among 14 measured serum cytokines, MCP-1 and KC-protein were significantly elevated from 0.5 h on. In conclusion, a fast induction of proinflammatory and stress-induced protective processes in brain dead donor kidneys was demonstrated, probably triggered by changes occurring during BD induction. Importantly, hypoxia appeared not to be one of the initial triggers, and early increased systemic levels of chemokines MCP-1 and KC may be regarded as the starting point for the inflammatory cascade in brain dead donor kidneys.

Neutrophil chemoattractant genes KC and MIP-2 are expressed in different cell populations at sites of surgical injury

KC and macrophage-inflammatory protein-2 (MIP-2) are CXC chemokines that exhibit distinct temporal patterns of expression in the skin following surgical injury. In situ hybridization analysis demonstrates that these two chemokines are expressed by distinct cell types at different times following injury. Dermal fibroblasts and endothelial cells are primarily responsible for KC expression in the skin 6 h following surgery. In contrast, MIP-2 production appears to be restricted to infiltrating inflammatory leukocytes including neutrophils and monocytes, which appear later in the response. This cell type-specific pattern of chemokine expression is recapitulated in vitro using isolated primary- and long-term-cultured cell types. Primary dermal fibroblasts stimulated with interleukin-1alpha express predominantly KC and very little MIP-2, and peritoneal exudate neutrophils produce as much or more MIP-2 as KC following stimulation in vitro. Although a collection of exogenous stimuli can induce expression of KC and MIP-2, the quantitative ratio for expression reflects the cell type and not the stimulus. The selective expression of KC over MIP-2 in endothelial cells results from markedly greater KC gene transcription and not from alterations in the rate of mRNA decay. These results demonstrate that distinct CXC chemokines show restricted expression in myeloid versus nonmyeloid cell types and that patterns of chemokine expression at sites of inflammation in vivo reflect the temporally ordered contribution of these distinct cell types.

Interleukin-1-mediated stabilization of mouse KC mRNA depends on sequences in both 5'- and 3'-untranslated regions

mRNA transcribed from the mouse KC chemokine gene accumulated to significantly higher levels in multiple cell types after treatment with interleukin 1alpha (IL-1alpha) as compared with tumor necrosis factor-alpha (TNFalpha). Although TNFalpha and IL-1alpha both signaled the activation of nuclear factor kappaB and enhanced transcription of the KC gene with equal potency, only IL-1alpha treatment resulted in stabilization of KC mRNA. Nucleotide sequences that confer sensitivity for IL-1alpha-mediated mRNA stabilization were identified within the 5'- and 3'-untranslated regions (UTRs) of KC mRNA using transient transfection of chimeric plasmids containing specific portions of KC mRNA linked to the chloramphenicol acetyltransferase (CAT) gene. When plasmids containing either the 3'- or 5'-UTR of KC mRNA were used, the half-life of CAT mRNA was unaltered either in untreated or IL-1alpha-stimulated cells. In contrast, CAT mRNA transcribed from plasmids that contained both the 5'- and 3'-UTRs of the KC mRNA decayed more rapidly than control CAT mRNA, and this enhanced decay was prevented in cells treated with IL-1alpha. A cluster of four overlapping AUUUA motifs within the 3'-UTR was required, whereas the 5'-UTR region exhibited orientation dependence. These findings indicate that cooperative function of the two nucleotide sequences involves a distinct signaling pathway used by IL-1alpha but not TNFalpha.

Cytokine-induced neutrophil chemoattractant mRNA expressed in cerebral ischemia

Cytokine-induced neutrophil chemoattractant (CINC), originally identified as a chemoattractant in rat kidney epithelial cells, is related to human 'gro' and murine 'KC'. The proteins encoded by these genes belong to the chemokine alpha superfamily, most of which have neutrophil chemotactic activity. Since brain chemokines may play a significant role in neutrophil accumulation in cerebral ischemia which can contribute to the extent of tissue injury in stroke, we examined the expression of CINC mRNA in the cerebral cortex of rats subjected to focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO). Significant CINC mRNA expression was observed in the ipsilateral (ischemic) cortex from 6 h (17.3 +/- 3.7%, n = 6, P < 0.05) to 24 h (32.1 +/- 3.7%, n = 5, P < 0.01) with a peak at 12 h (43.9 +/- 3.7%, n = 6, P < 0.01) after MCAO. Five days post-MCAO, CINC mRNA levels were no longer elevated. No significant CINC mRNA expression was observed in the contralateral (control) cortex. These studies suggest that message for the neutrophil chemoattractant CINC is induced early in brain tissue subjected to ischemia, and therefore supports the possibility that brain-derived chemokines support the infiltration of circulating inflammatory cells following focal stroke.