Receptor-independent intracellular radical scavenging activity of an angiotensin II receptor blocker.
OBJECTIVE
Angiotensin II plays a crucial role in the induction of oxidative stress and the pathogenesis of cardiovascular and renal diseases, and the beneficial mechanisms of angiotensin II receptor 1 blockers (ARBs) are multifactorial. We investigated the receptor-independent protective role of an ARB using primary-cultured mesangial cells from angiotensin II receptor 1 knockout or wild-type mice and a highly lipophilic ARB, telmisartan.


RESULTS
Intracellular reactive oxygen species were estimated using a fluorogenic probe, CM-H2DCFDA. Non-angiotensin II-induced reactive oxygen species production was generated by exposing cells to hydrogen peroxide alone or after treatment with telmisartan. Flow cytometry analysis showed that angiotensin II induced an increase in oxidant production in a dose-dependent manner in wild-type cells, but not in knockout cells. In contrast, hydrogen peroxide induced oxidative stress in both wild-type and knockout cells. Interestingly, telmisartan attenuated the oxidative stress induced by hydrogen peroxide in both cells, suggesting that it acted via a receptor-independent antioxidant effect. Intracellular concentrations of telmisartan were confirmed by high-performance liquid chromatography analysis. Expression of plasminogen activator inhibitor 1, which is stimulated by oxidative stress, was also attenuated by telmisartan in a receptor-independent as well as receptor-dependent manner. Telmisartan did not change expression levels of antioxidative enzymes such as catalase or glutathione peroxidase. Furthermore, the amelioration of oxidative stress by telmisartan did not involve the peroxisome proliferator-activated receptor-gamma pathway.


CONCLUSIONS
Telmisartan inhibits intracellular oxidative stress, at least in part, in a receptor-independent manner, possibly owing to its lipophilic and antioxidant structure.
Shao
Jing
J
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Nangaku
Masaomi
M
Inagi
Reiko
R
Kato
Hideki
H
Miyata
Toshio
T
Matsusaka
Taiji
T
Noiri
Eisei
E
Fujita
Toshiro
T
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D001562:Benzimidazoles / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D017931:DNA Primers; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D018384:Oxidative Stress; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species; D011945:Receptors, Angiotensin / Q000235:genetics / Q000502:physiology; D000077333:Telmisartan; D015854:Up-Regulation
D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001565:Benzoates; D017931:DNA Primers; D016166:Free Radical Scavengers; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D011945:Receptors, Angiotensin; D000077333:Telmisartan