KALLIKREIN GENE-THERAPY IN NEWBORN AND ADULT HYPERTENSIVE RATS

The tissue kallikrein-kinin system has been postulated to play an impo rtant role in blood pressure regulation. Kallikreins are serine protei nases that release potent vasodilating kinin peptides from precursor k ininogens by limited proteolysis. Our recent studies show that systemi c delivery of the human tissue kallikrein gene into adult spontaneousl y hypertensive rats (SHR) results in a sustained reduction of blood pr essure for several weeks. The goal of this study is to evaluate whethe r early delivery of the kallikrein gene into newborn SHR could exert a suppressive effect on blood pressure phenotype during rat growth and development. A human tissue kallikrein cDNA construct, under the contr ol of cytomegalovirus promoter (CMV-cHK), or vector DNA was injected s ubcutaneously into the necks of 2-day-old SHR. Blood pressures were mo nitored biweekly from 3 to 19 weeks by the tail-cuff method. A single injection of the human kallikrein cDNA construct caused a significant reduction of blood pressure (n = 6, p < 0.001) from 11 to 17 weeks aft er injection compared with control rats receiving vector DNA. Intraven ous delivery of the human tissue kallikrein gene into adult SHR produc ed blood pressure lowering effects (n = 6,p < 0.001) that lasted for 6 weeks in male but not in female rats. The expression of human tissue kallikrein in rats was identified by reverse transcription polymerase chain reaction followed by Southern blot analysis and an ELISA specifi c for human tissue kallikrein. Kallikrein gene delivery did not cause any changes in body weight, urine volume, or water intake in the exper imental animals compared with the control group. No antibodies to eith er human tissue kallikrein or its DNA were detected in rat sera 19 wee ks postinjection. These results show that delivery of the kallikrein g ene at an early stage of life has a protective effect against developm ent of hypertension in adult SHR and that gender differences could be a factor in kallikrein gene therapy for the treatment of hypertensive disorders.