Effect of alternate-day hydrocortisone therapy on the immunologically immature rat. I: Effect on blood cell count, immunoglobulin concentrations, and body and organ weights

The pharmacokinetic and biological activity profile of dexamethasone targeted to sinusoidal endothelial and Kupffer cells

Dexamethasone (Dexa) was coupled to human serum albumin (Dexa10-HSA) for the targeting of this anti-inflammatory drug to Kupffer cells (KC) and sinusoidal endothelial cells (SEC) in the liver: key players in the pathogenesis of acute and chronic inflammatory liver diseases like fibrosis. Cell-specific delivery of Dexa may increase its efficacy and prevent side effects. We, therefore, studied the pharmacokinetic profile, efficacy, and toxicity of Dexa10-HSA in bile duct ligation (BDL)-induced fibrosis in rats.

RESULTS

Dexa10-HSA was taken up by scavenger receptors on KC and SEC and was rapidly cleared from the blood stream, with no differences in kinetic parameters between normal and fibrotic rats. KC isolated from livers of rats treated wi th Dexa10-HSA were unresponsive to lipopolysaccharide in contrast to controls. A dose of 0.1 mg kg(-1) three times a week reduced intrahepatic reactive oxygen species production strongly as compared to untreated BDL rats. This dose, however, also stimulated the depositions of collagens I and III. Overdosing of Dexa10-HSA (10 mgkg(-1)) led to a lethal reduction of body and spleen weight.

CONCLUSIONS

Dexa10-HSA has potent anti-inflammatory effects during BDL at extremely low doses, demonstrating the cell-specific targeting. However, the fibrotic process was not favourably affected. These results indicate a dual role for Dexa; besides blocking the release of pro-inflammatory cytokines it also reduces the release of antifibrotic mediators by SEC and KC.

Electron microscopic study on the effect of alternate-day hydrocortisone therapy on lymphocyte populations in rat spleen and lymph nodes

The ultrastructural effects of 400 mg/M2/day of hydrocortisone sc, given alternatively from day 7 through day 19, were studied on the lymphocyte populations in the white pulp of the spleen and in the cortex of the mesenteric lymph nodes of the immunologically immature rat. Results were consistent with both a direct lytic effect of hydrocortisone on small lymphocytes of the nodular cortex of the mesenteric lymph nodes and an indirect effect on small lymphocytes of the periarterial lymphatic sheath (PALS) of the spleen supplied via the thymus. In contrast, medium-sized lymphocytes in the PALS appeared to be unaffected by hydrocortisone, while medium-sized lymphocytes of the nodular cortex of the mesenteric lymph nodes exhibited a temporary depletion of cytoplasmic organelles. Hydrocortisone appeared to depress protein synthesis in these latter cells. The decrease in numbers of lymphoblasts and plasmablasts observed in the nodular cortex of the mesenteric lymph nodes and the white pulp of the spleen is consistent with hydrocortisone interference with proliferation and differentiation of activated B cells.