Kaspareit-Rittinghausen described a rodent model of inherited polycystic kidney disease (PKD), the Han:SPRD rat [1, 2], in which heterozygotes develop renal cysts and renal failure (in males) over several months, whereas homozygous animals develop rapidly progressive renal enlargement that leads to death in a few weeks. In this study, we examined selected elements of the pathogenesis of this disease in heterozygotes and homozygotes from birth to advanced disease. Heterozygous male rats developed slowly progressive renal cystic disease with interstitial fibrosis and azotemia seen by six months of age. Female heterozygotes developed slowly progressive renal cystic disease, but did not develop interstitial fibrosis or azotemia. Epithelial cells lining cyst cavities showed various degrees of morphologic immaturity. Cyst walls also developed basement membrane thickening, especially in areas of cellular immaturity, suggesting an interrelationship between this basement membrane thickening and cellular dedifferentiation. Thickened basement membranes were associated with increased immunoreactivity for type IV collagen, laminin, and fibronectin. Homozygous rats developed massive renal enlargement, marked azotemia, and died near three weeks of age. Renal c-myc proto-oncogene expression was elevated in homozygous cystic infants and in adult heterozygotes. In situ hybridization showed high levels of c-myc mRNA in cyst epithelia, suggesting abnormal regulation of cellular proliferation in the cells lining cysts, as seen in other models of PKD. The Han:SPRD rat is the only well-documented animal model of inherited PKD with an autosomal-dominant inheritance pattern and appears to have several features which resemble human ADPKD.

The global regulator CsrA (carbon storage regulator) of Escherichia coli is a small RNA binding protein that represses various metabolic pathways and processes that are induced in the stationary phase of growth, while it activates certain exponential phase functions. Both repression and activation by CsrA involve posttranscriptional mechanisms, in which CsrA binding to mRNA leads to decreased or increased transcript stability, respectively. CsrA also binds to a small untranslated RNA, CsrB, forming a ribonucleoprotein complex, which antagonizes CsrA activity. We have further examined the regulatory interactions of CsrA and CsrB RNA. The 5 end of the CsrB transcript was mapped, and a csrB::cam null mutant was constructed. CsrA protein and CsrB RNA levels were estimated throughout the growth curves of wild-type and isogenic csrA, csrB, rpoS, or csrA rpoS mutant strains. CsrA levels exhibited modest or negligible effects of these mutations. The intracellular concentration of CsrA exceeded the total CsrA-binding capacity of intracellular CsrB RNA. In contrast, CsrB levels were drastically decreased (ϳ10-fold) in the csrA mutants. CsrB transcript stability was unaffected by csrA. The expression of a csrB-lacZ transcriptional fusion containing the region from ؊242 to ؉4 bp of the csrB gene was decreased ϳ20-fold by a csrA::kanR mutation in vivo but was unaffected by CsrA protein in vitro. These results reveal a significant, though most likely indirect, role for CsrA in regulating csrB transcription. Furthermore, our findings suggest that CsrA mediates an intriguing form of autoregulation, whereby its activity, but not its levels, is modulated through effects on an RNA antagonist, CsrB.

No abstract

Human peripheral blood mononuclear cells (PBMCs) were cultured in vitro with various stimuli and in the presence or absence of a 5-lipoxygenase (5-LO) inhibitor, A-63162, to measure its effects on PBMC proliferation, interleukin-2 receptor (IL-2R) expression, interleukin-2 (IL-2) synthesis, interleukin-6 (IL-6) synthesis, and accumulation of messenger RNA for IL-2 or IL-6. A-63162 inhibited PBMC proliferation stimulated by phytohemagglutinin (PHA) and phorbol myristate acetate (PMA) plus A23187, IL-2 receptor expression stimulated by PHA, and IL-2 or IL-6 synthesis induced by PHA plus PMA or PMA plus A23187. At the same concentration, A-63162 inhibited accumulation of mRNA for IL-2 or IL-6 and also inhibited leukotriene B4 (LTB4) synthesis. Our data indicate that the 5-LO inhibitor A-63162 has immunosuppressive activity that may be due to inhibition of LTB4 production or to direct inhibitory actions of A-63162 on IL-2 and IL-6 synthesis.