Contributions of angiotensin II and tumor necrosis factor-alpha to the development of renal fibrosis

Role of TNF-alpha receptors in mice intoxicated with the parkinsonian toxin MPTP

The loss of dopaminergic neurons in Parkinson's disease is associated with a glial reaction and the overproduction of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha). TNF-alpha acts via two different receptors, TNFR1 and TNFR2, and is believed to have both a neuroprotective and a deleterious role for neurons. In order to analyze the putative role of TNF-alpha in parkinsonism, we compared the effect of the parkinsonian drug 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice lacking TNFR1, TNFR2, or both receptors and in wild-type littermates. We show that MPTP does not affect spontaneous activity or anxiety in any of the groups and that it reduces motor activity on a rotarod in double knock out mice but not in mice lacking only one receptor. Postmortem analysis revealed no differences in the number of nigral dopaminergic neurons whatever the group. In contrast, striatal dopamine level was slightly decreased in double knock-out mice and more reduced by MPTP in this group than in the other groups of mice. In addition, dopamine turnover was significantly more increased in double knock out mice after MPTP injection. These data suggest that TNF-alpha does not participate in the death of dopaminergic neurons in parkinsonism but that it slightly alters dopamine metabolism or the survival of dopaminergic terminals by a mechanism involving both receptors.

A gene expression analysis in rat kidney following high and low salt intake

BACKGROUND

The effects of salt intake on renal regulation have been investigated for decades. To find new pathways and to demonstrate the utility of oligonucleotide expression arrays, we studied whole kidneys.

METHODS

Eight Sprague-Dawley rats were divided into two groups. One group received a 6% salt (by weight) diet, while the other group received a 0.3%, otherwise identical, salt diet for 7 days. The rats were sacrificed after 7 days and the left kidney was subjected to RNA extraction. Oligonucleotide expression arrays (Affymetrix) were used to determine downregulation and upregulation, comparing high with low salt intake. Four rats from each group were studied separately.

RESULTS

The experiments were reproducible. Thirty genes were downregulated with the high-salt diet, while 35 genes were upregulated. The renin gene, beta-2 glycoprotein-1, retinol binding protein, annexin VI, and the PTP2C protein tyrosine phosphatase were among the downregulated genes. The angiotensin II receptor type 1B receptor, HMG-CoA reductase, B7 antigen, and the rat calcium channel beta subunit III were among the upregulated genes. Differentially regulated were the p55 subunit (upregulated) and the p50 subunit (downregulated) of the phosphatidyl inositol 3-kinase enzyme complex. We verified our results by selecting a high-salt downregulated gene (renin) and an upregulated gene (B7 antigen) and subjecting these genes to real-time polymerase chain reaction. The results were consistent.

CONCLUSION

Oligonucleotide expression arrays can detect novel genes encoding for proteins not generally associated with responses to varied salt intake. Experiments of this nature have substantial limitations and require detailed verification. However, overall, the utility is promising.