sirolimus and 3-nitrotyrosine

Reactive oxygen species play a dual role in mediating both cell stress and defense pathways. Here, we used pharmacological manipulations and siRNA silencing to investigate the relationship between autophagy and oxidative stress under conditions of noise-induced temporary, permanent, and severe permanent auditory threshold shifts (temporary threshold shift [TTS], permanent threshold shift [PTS], and severe PTS [sPTS], respectively) in adult CBA/J mice.. Levels of oxidative stress markers (4-hydroxynonenal [4-HNE] and 3-nitrotyrosine [3-NT]) increased in outer hair cells (OHCs) in a noise-dose-dependent manner, whereas levels of the autophagy marker microtubule-associated protein light chain 3 B (LC3B) were sharply elevated after TTS but rose only slightly in response to PTS and were unaltered by sPTS noise. Furthermore, green fluorescent protein (GFP) intensity increased in GFP-LC3 mice after TTS-noise exposure. Treatment with rapamycin, an autophagy activator, significantly increased LC3B expression, while diminishing 4-HNE and 3-NT levels, reducing noise-induced hair cell loss, and, subsequently, noise-induced hearing loss (NIHL). In contrast, treatment with either the autophagy inhibitor 3-methyladenine (3MA) or LC3B siRNA reduced LC3B expression, increased 3-NT and 4-HNE levels, and exacerbated TTS to PTS.. This study demonstrates a relationship between oxidative stress and autophagy in OHCs and reveals that autophagy is an intrinsic cellular process that protects against NIHL by attenuating oxidative stress.. The results suggest that the lower levels of oxidative stress incurred by TTS-noise exposure induce autophagy, which promotes OHC survival. However, excessive oxidative stress under sPTS-noise conditions overwhelms the beneficial potential of autophagy in OHCs and leads to OHC death and NIHL.

Topics: Acetylcysteine; Aldehydes; Animals; Antioxidants; Autophagy; Hair Cells, Auditory, Outer; Hearing Loss, Noise-Induced; Male; Mice; Microtubule-Associated Proteins; Oxidative Stress; Sirolimus; Tyrosine

To evaluate the role of rapamycin in the prevention of diabetic oxidative stress and the regulation of angiogenic factors.. Experimental animal study.. Diabetes was induced in 20 adult male Wistar rats by a single intraperitoneal administration of streptozotocin (60 mg/kg). Rats were randomly assigned into diabetic and rapamycin groups (n = 10). Ten healthy normal adult male rats of same age formed the control group. All groups were followed for 3 months. Rapamycin group received 1 mg/kg rapamycin via orogastric gavage during the last 4 weeks. At the end of 12 weeks, rats were sacrificed and biochemical oxidative stress markers (malondialdehyde and nitrotyrosine), together with vascular endothelial growth factor, hypoxia-inducible factor-1α, and pigment epithelium-derived factor, were measured in the retina. Blood biochemical analyses were also done.. In the diabetic group, retinal malondialdehyde and nitrotyrosine levels were increased in comparison with control and rapamycin groups (p < 0.05). Rapamycin suppressed oxidative stress and showed a beneficial effect. It also decreased all angiomodulator cytokines compared with the diabetic group (p < 0.05). Correspondingly, rapamycin also decreased plasma malondialdehyde levels compared with the diabetic group (p = 0.037).. Rapamycin may have a protective role against diabetes-induced oxidative retinal injury and may decrease angiomodulator cytokines.

Topics: Angiogenesis Modulating Agents; Animals; Anti-Bacterial Agents; Diabetes Mellitus, Experimental; Diabetic Retinopathy; Eye Proteins; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Malondialdehyde; Nerve Growth Factors; Oxidative Stress; Rats; Rats, Wistar; Serpins; Sirolimus; Tyrosine; Vascular Endothelial Growth Factor A