The effect of aging on the genetic expression of renin by mouse kidney

Lineage tracing aged mouse kidneys shows lower number of cells of renin lineage and reduced responsiveness to RAAS inhibition

Blocking the renin-angiotensin-aldosterone system (RAAS) remains a mainstay of therapy in hypertension and glomerular diseases. With the population aging, our understanding of renin-producing cells in kidneys with advanced age is more critical than ever. Accordingly, we administered tamoxifen to Ren1cCreERxRs-tdTomato-R mice to permanently fate map cells of renin lineage (CoRL). The number of Td-tomato-labeled CoRL decreased significantly in aged mice (24 mo of age) compared with young mice (3.5 mo of age), as did renin mRNA levels. To determine whether aged CoRL responded less to RAAS blockade, enalapril and losartan were administered over 25 days following uninephrectomy in young and aged mice. The number of CoRL increased in young mice in response to enalapril and losartan. However, this was significantly lower in aged mice compared with young mice due to limited proliferation, but not recruitment. Gene expression analysis of laser-captured CoRL showed a substantial increase in mRNA levels for proapoptotic and prosenescence genes, and an increase in a major prosenescence protein on immunostaining. These results show that CoRL are lower in aged mice and do not respond to RAAS inhibition to the same extent as young mice.

The mechanism of increased renal susceptibility to toxic substances in the elderly. Part I. The role of increased vasoconstriction

The mechanisms of increased susceptibility to nephrotoxins in aging are complex and incompletely understood. It is very important to try to increase our knowledge of them because adults become increasingly vulnerable to nephrotoxic substances, as they grow older. In addition, the percentage of elderly people will increase markedly in the near future, at least in the developed countries. Drugs such as diuretics, laxatives, NSAIDs, aminoglycosides and other nephrotoxic antibiotics, and converting enzyme inhibitors are used a lot by aging people and can produce severe renal problems. Beside drugs, the clinical use of radiocontrast agents also rises in older patients. It seems that the main mechanism of the increased renal susceptibility to toxic substances in the elderly is a disbalance between vasoconstrictor and vasodilator factors (in favor of vasoconstrictor ones). Increased propensity to vasoconstriction (to Ang II, ET and PAF), as well as increased levels of oxidatively modified biomolecules in the elderly, may enhance susceptibility of old kidney to toxic substances. In addition, all mechanisms that influence both mesangial and fibroblast cell proliferation and over-production of extracellular matrix might also be involved in the processes that make the old kidney prone to drug-induced chronic toxic injury.