Albumin activation of NAD(P)H oxidase activity is mediated via Rac1 in proximal tubule cells.
BACKGROUND
Rac1 is a Rho-family small GTP-ase, when activated is pivotal in NAD(P)H oxidase (NOX) activation and generation of reactive oxygen species (ROS). Evidence links Rac1 activation to receptor-mediated albumin endocytosis in the proximal tubule cell (PTC). Thus in states of albumin overload, Rac1 activation could lead to NOX activation and ROS formation in the PTC. Furthermore, accumulating evidence supports that HMG-CoA reductase inhibition may reduce oxidative stress and albuminuria.


METHODS
To investigate the role of HMG-CoA reductase inhibition of Rac1 and oxidative stress we used the opossum kidney PTC. ROS generation in the PTC was confirmed using oxidative fluorescent dihydroethidium staining.


RESULTS
We observed time-dependent increases in NOX activity with bovine serum albumin (albumin) stimulation (500 microg/dl, maximum at 20 min, p < 0.05) that was inhibited in a concentration-dependent manner with the HMG-CoA reductase inhibitor rosuvastatin (1 microM, p < 0.05). Additionally, the Rac1 inhibitor NSC23766 (100 ng/ml) attenuated albumin activation of NOX. Western blot analysis confirmed Rac1 translocation to plasma membrane in the PTC following albumin stimulation and subsequent inhibition by rosuvastatin and NSC23766.


CONCLUSIONS
These data demonstrate that albumin-mediated increases in NOX activity and ROS in PTC are reversed by inhibition of Rac1 signaling with the use of rosuvastatin.
Whaley-Connell
Adam T
AT
Department of Internal Medicine, University of Missouri School of Medicine, Columbia, MO 65212, USA. whaleyconnella@health.missouri.edu
Morris
E Matthew
EM
Rehmer
Nathan
N
Yaghoubian
J Cipporah
JC
Wei
Yongzhong
Y
Hayden
Melvin R
MR
Habibi
Javad
J
Stump
Craig S
CS
Sowers
James R
JR
D000418:Albumins / Q000187:drug effects / Q000378:metabolism*; D000419:Albuminuria / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004195:Disease Models, Animal; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D005464:Fluorobenzenes / Q000494:pharmacology; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018613:Microscopy, Confocal; D019255:NADPH Oxidases / Q000378:metabolism*; D009893:Opossums; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D011743:Pyrimidines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D000068718:Rosuvastatin Calcium; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000418:Albumins; D000634:Aminoquinolines; D016895:Culture Media, Serum-Free; D005464:Fluorobenzenes; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; C487513:NSC 23766; D011743:Pyrimidines; D017382:Reactive Oxygen Species; D013449:Sulfonamides; D000068718:Rosuvastatin Calcium; D019255:NADPH Oxidases; D020830:rac1 GTP-Binding Protein