No abstract

This article describes the modulation, by extracellular collagen, of DNA and proteoglycan synthesis in articular chondrocytes stimulated with transforming growth factor-beta 1. Type-I and type-II collagen, heat-denatured type-II collagen, and bovine serum albumin were each incorporated into alginate in increasing concentrations. Bovine articular chondrocytes were isolated and were resuspended in the alginate, yielding alginate beads with final extracellular protein concentrations of 0-1.5% (wt/vol) for the collagens and 0-2.5% (wt/vol) for bovine serum albumin. Cultures of beads were maintained for 7 days in basal Dulbecco's modified Eagle medium or in medium supplemented with 10 ng/ml transforming growth factor-beta 1. Subsequently, the synthesis of DNA and proteoglycan was measured by radiolabel-incorporation methods with [35S]sulfate and [3H]thymidine, and the values were normalized to the DNA content. Transforming growth factor-beta 1 stimulated the synthesis of both DNA and proteoglycan in a bimodal fashion. The presence of extracellular type-II collagen increased the rate of DNA and proteoglycan synthesis in a dose-dependent fashion in cultures stimulated by transforming growth factor-beta 1, whereas heat-inactivated type-II collagen abrogated the effects observed with type-II collagen for synthesis of both DNA and proteoglycan. In contrast, the presence of extracellular type-I collagen caused a dose-dependent inhibition of synthesis of both DNA and proteoglycan in cultures stimulated with transforming growth factor-beta 1. Extracellular bovine serum albumin brought about a limited increase in synthesis rates, presumably by blocking nonspecific cytokine binding. These results suggest that type-II collagen has a specific role in chondrocyte regulation and serves to mediate the response of chondrocytes to transforming growth factor-beta 1.

The process of dendritic cell (DC) maturation, critical for effective DC-based immunotherapy, also alters the proteasome such that peptides presented in the context of HLA class I are generated not by the constitutive proteasome, but by the immunoproteasome. Cytotoxic

This study examined the effects of 1400W, an inhibitor of inducible nitric oxide (iNOS), on contractile function and iNOS expression in reperfused skeletal muscle. The right extensor digitorum longus (EDL) muscle of 104 rats underwent a sham operation or 3-h ischemia followed by 3-h or 24-h reperfusion (I/R). Rats received 3 mg/kg 1400W, 10 mg/kg 1400W, or water subcutaneously. Results showed that EDL contractile function in both 1400W-treated groups significantly outperformed the controls at 24-h but not at 3-h reperfusion. Although iNOS expression increased in all three I/R groups during reperfusion, a significantly smaller increase was found in 1400W-treated muscles after 3-h reperfusion, and more dramatically so after 24-h reperfusion. Our results indicate that inhibition of iNOS preserved the contractile function in reperfused skeletal muscle, perhaps via downregulating iNOS expression. Protection by 1400W at 24-h reperfusion suggests that the role of iNOS in exaggerating reperfusion injury is more prominent in the later stages of injury.