Estrogen protects cardiac myogenic (H9c2) rat cells against lethal heat shock-induced cell injury: modulation of estrogen receptor alpha, glucocorticoid receptors, heat shock protein 70, and iNOS.
In the present study we have established that exposure of rat cardiac myoblasts (H9c2 cells) to 46 degrees C for 1 hour (lethal heat shock) resulted in optimal cell injury as determined by lactate dehydrogenase release. Pretreatment of H9c2 cells for 24 hours with 17beta-estradiol significantly protects myoblasts against subsequent lethal heat shock exposure in a concentration-dependent manner with maximum protection obtained at 1 microM of 17beta-estradiol. With Western blotting, it was observed that 17beta-estradiol-protected cells had significantly higher levels of the estrogen receptor alpha and inducible heat shock protein 70 (hsp70) as well as inducible nitric oxide synthase (iNOS) levels compared with lethal heat shock-exposed cells. In contrast, lethal heat shock-exposed cells had significantly higher levels of total cellular glucocorticoid receptors (GR), both cytoplasmic and nuclear, compared with 17beta-estradiol-protected cells. Immunofluorescence technique using confocal microscopy revealed nuclear localization of the glucocorticoid receptors (GR) in lethal heat shock-exposed H9c2 cells while 17beta-estradiol-protected cells had primarily extranuclear localization of GR. We conclude that (1) 17beta-estradiol protects H9c2 cells against lethal heat shock insult by a receptor-independent mechanism, and (2) the protective effects are likely mediated by modulation of GR, hsp 70, and iNOS expression.
Al-Khlaiwi
Thamir
T
Department of Physiology, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298-0551, USA.
Al-Drees
Abdulmajeed
A
Gursoy
Erdal
E
Qureshi
Ian
I
Biber
Thomas
T
Kalimi
Mohammed
M
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000187:drug effects*; D047629:Estrogen Receptor beta / Q000187:drug effects; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D006358:Hot Temperature; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000473:pathology*; D019001:Nitric Oxide Synthase / Q000378:metabolism / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000187:drug effects*; D012769:Shock / Q000473:pathology*
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D018840:HSP70 Heat-Shock Proteins; D011965:Receptors, Glucocorticoid; D004958:Estradiol; D007770:L-Lactate Dehydrogenase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat