Protective effect of 20-hydroxyeicosatetraenoic acid (20-HETE) on glomerular protein permeability barrier.
BACKGROUND
Proteinuria is a significant problem in medicine today, although glomerular events underlying it are unknown. Products of cytochrome P450 (CYP450) pathway of arachidonic acid metabolism are increasingly recognized as playing major roles in renal function. We used in vitro albumin permeability (P(alb)) as a measure of injury and puromycin aminonucleoside (PAN) as an injurious agent to test the hypothesis that 20-hydroxyeicosatetraenoic acid (20-HETE) protects the glomerular filtration barrier from increased P(alb).


METHODS
We determined P(alb) in the following experimental groups: (1) isolated rat glomeruli incubated with PAN (5 microg/mL) for 5, 15, 30 or 60 minutes; (2) isolated glomeruli preincubated with 20-HETE (1.0 nmol/L to 100 nmol/L) for 15 minutes followed by additional incubation with PAN (5 microg/mL) for 15 minutes; (3) isolated glomeruli from rats treated with the CYP450 4A inducer clofibrate, and incubated with PAN (5 microg/mL) for 15 minutes; and (4) appropriate controls for each group. CYP450 4A levels were measured in glomeruli isolated from rats treated with clofibrate or vehicle.


RESULTS
PAN increased P(alb) of isolated glomeruli as early as 5 minutes (P(alb) 0.33 +/- 0.21, P < 0.05 vs. control). Maximal effect occurred at 30 minutes (P(alb) 0.75 +/- 0.16, P < 0.001 vs. control). Inclusion of 20-HETE (100 nmol/L) blocked the increased P(alb) caused by PAN (P(alb) 0.05 +/- 0.13). Likewise, glomeruli isolated from rats treated with clofibrate were protected from PAN-induced increase in P(alb) (P(alb) 0.19 +/- 0.03). Treatment with clofibrate significantly increased glomerular CYP450 4A expression.


CONCLUSIONS
PAN directly and immediately affects the glomerular permeability barrier. Furthermore, exogenous 20-HETE or clofibrate treatment protects glomeruli from increased P(alb) caused by PAN. Relative lack of 20-HETE may be a general characteristic of proteinuric states. Conversely, measures used to treat and/or prevent proteinuria may act to restore or increase glomerular 20-HETE levels.
McCarthy
Ellen T
ET
Divison of Nephrology, Medical College of Wisconsin, Milwaukee, Wisconsin.
Sharma
Ram
R
Sharma
Mukut
M
D000818:Animals; D002994:Clofibrate / Q000494:pharmacology; D042926:Cytochrome P-450 CYP4A / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006893:Hydroxyeicosatetraenoic Acids / Q000378:metabolism / Q000494:pharmacology*; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D010539:Permeability / Q000187:drug effects; D011507:Proteinuria / Q000209:etiology / Q000378:metabolism; D011692:Puromycin Aminonucleoside / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley
D006893:Hydroxyeicosatetraenoic Acids; D011692:Puromycin Aminonucleoside; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D003577:Cytochrome P-450 Enzyme System; D042926:Cytochrome P-450 CYP4A; D002994:Clofibrate