Developmentally Regulated Expression of theCYP4AGenes in the Spontaneously Hypertensive Rat Kidney

Abstract

SUMMARYThe CYP4A enzymes catalyze the formation of 20-hydroxyeicosatetraenoic acid (20-HETE), which has potent effects on the renal vasculature and tubular ion transport. Based on an increased 20-HETE formation in renal microsomes from spontaneously hypertensive rats, it has been proposed that increased expression of the CYP4A genes is an early event in the development of hypertension in these animals. To test this hypothesis, we developed RNase protection assays for specific detection of the individual CYP4A genes in the kidneys of spontaneously hypertensive and Wistar-Kyoto rats. Distinct age-dependent patterns of expression were observed for the individual CYP4A genes, with only CYP4A3 mRNA measurable in the kidneys of 1-week-old rats. CYP4A1 and CYP4A8 mRNA were detectable by 3 weeks of age and CYP4A2 mRNA at 5 weeks of age. The expression of CYP4A1 and CYP4A3 varied 4 -5-fold throughout development and was highest between 3 and 5 weeks of age, declining steadily thereafter to 20% of their maximal level by 9 weeks of age. CYP4A2 mRNA levels increased steadily between 5 and 9 weeks of age, whereas CYP4A8 mRNA levels were relatively constant throughout development. The CYP4A3 mRNA level was significantly increased 1.6 -2-fold in the cortex and outer medulla of 1-4-week-old spontaneously hypertensive rat kidneys relative to the corresponding level in the Wistar-Kyoto. A similar 1.4 -1.7-fold increase in CYP4A8 mRNA was also found in 3-and 4-weekold spontaneously hypertensive kidneys. Accompanying the increased expression of CYP4A3 and CYP4A8 mRNA in the prehypertensive rats were corresponding changes in functional CYP4A measured as either arachidonic acid or lauric acid -hydroxylase activity (1.4 -2.0-fold increases) and CYP4A protein levels. After 4 weeks of age, the level of CYP4A mRNA, enzyme activity, and protein were similar in the kidneys of Wistar-Kyoto and spontaneously hypertensive rats. The findings suggest that the expression of CYP4A3 and CYP4A8 may be critical to the early changes in eicosanoid formation and renal function in the young spontaneously hypertensive rat.

Elevated production of 20-HETE in the cerebral vasculature contributes to severity of ischemic stroke and oxidative stress in spontaneously hypertensive rats

“…In the present study, animals were pretreated with HET0016 for 5 min before MCAO to determine the contribution of 20-HETE to ischemic stroke outcomes in normotensive and hypertensive rats. Administration of HET0016 also reduced MAP in SHR and SHRSP by about 30 mmHg, which is consistent with previous suggestions that elevated vascular production of 20-HETE may contribute to increased peripheral vascular tone and the maintenance of hypertension in the SHR (17,30,52,63,64,67). This reduction in MAP in SHR and SHRSP may also contribute to the reduction in infarct size with HET0016 treatment by reducing the driving force for edema formation.…”

Antihypertensive effect of mechanism-based inhibition of renal arachidonic acid ω-hydroxylase activity

“…A sim-ilar pattern was also found with ABT and in earlier studies with the heme oxygenase inducer stannous chloride (29,42). During the period when blood pressure rises rapidly in the SHR (5-9 wk of age), 20-HETE formation in renal microsomes is elevated relative to age-matched WKY rats (27,37), and there is a decreased diameter of interlobular and afferent arterioles that can be reversed by blockade of renal 20-HETE formation (12,15,19). The elevation of medullary vascular resistance associated with decreased papillary blood flow contributes to an upward shift of the pressure-natriuresis relationship in the early developmental phase of hypertension in SHRs, and 20-HETE has been implicated in this response (40).…”

“…Age-dependent changes in CYP eicosanoid production are well documented in renal microsomes from the spontaneously hypertensive rat (SHR), and increased renal CYP4A3 mRNA and CYP4A-immunoreactive protein levels are consistent with the increased -and ( -1)-hydroxylation of arachidonic acid in the prehypertensive SHR kidney relative to agematched normotensive Wistar-Kyoto (WKY) rats (27,37,51). The increased 20-HETE formation in young SHRs is accompanied by a decreased diameter of interlobular arteries and afferent arterioles relative to the WKY rat (19).…”

“…The reaction was stopped after 30 min by the addition of 1 N HCl to a final pH of 3-3.5. Arachidonic acid and its metabolites were extracted and quantified by HPLC with radiometric detection as described previously (27). Epoxygenase activity is reported as the sum of EET and DHET formation.…”

Determination of the Dominant Arachidonic Acid Cytochrome P450 Monooxygenases in Rat Heart, Lung, Kidney, and Liver: Protein Expression and Metabolite Kinetics

“…Renal 20-HETE levels are increased in the spontaneously hypertensive rat model of essential hypertension (14). Moreover, inhibition of 20-HETE increased urinary excretion of sodium, without altering renal hemodynamics in Ren-2 transgenic rats (15).…”