Objectives: Evaluation of effect of 7-day prophylactic use of Geranylgeranylacetone (GGA) before acute noise exposure (ANE) on rat cochlear tissue homogenate (CTH) levels of HSP 70, malondialdehyde (MDA), and activity of antioxidant enzymes and find a relation between CTH and serum levels of HSP70.Materials & Methods: Thirty-two male albino rats divided into 4 equal groups: Group I received no prophylaxis or exposure to noise, Group II exposed to a 115 dB octave band noise centered at 4 kHz for 6-h without prophylaxis, Group III and IV included animals received GGA (600mg/kg/day for 7 days) without noise exposure or before exposure, respectively, to noise as for group II. Twenty-four hours after noise exposure, blood samples were taken from all animals for estimation of serum levels of HSP 70. Then, animals were sacrificed and skull was opened immediately for extraction of both cochleas that were homogenized for estimation for levels of HSP 70, MDA and activity of antioxidants.Results: MDA content was significantly higher, but levels and activities of antioxidant enzymes were significantly lower in CTH of group II than other groups. Mean CTH levels of HSP70 were significantly higher in animals of Group IV compared to other groups and in Group II compared to groups I and III with non-significantly higher levels in Group III than Group I. Serum HSP70 levels were significantly higher in Group IV than other groups and in Group II than group I. In control group, there was positive significant correlation (r=0.893, p=0.003) between HSP 70 serum and CTH levels.Conclusion: ANT induces cochlear tissue oxidative stress; however, prophylactic GGA therapy could ameliorate this effect through increasing cochlear tissue HSP70 expression levels. ELISA estimation of serum HSP70 levels could reflect its tissue levels and could be used as non-invasive diagnostic modality for impact of stresses |
