SSISPA 2011 Report

ABSTRACT

Background - Asthma is a chronic inflammatory condition in which airway smooth muscle is hyper responsive to spasmogens like histamine and carbachol. It is reported that it is due to damage of epithelium of airway smooth muscle by hydrogen peroxide (H2O2) free radical released in the inflammatory reactions. Recently, it is documented that use of antioxidants for scavenging free radicals not only blocked the effects of H2O2 but also attenuated hyper responsive airway smooth muscle to various spasmogens. With this back drop, an attempt was made to study whether curcumin a natural phytochemical that is reported to be having anti-inflammatory, antioxidant activities can reduce hyper activity induced by the H2O2 in air way smooth muscle.

Methods - Sheep trachea were obtained from the slaughter house and immediately transported in chilled modified Krebs-Henseleit solution to the laboratory within 30 minutes of slaughter. Tracheal smooth muscles were dissected and suspended in 20 ml aerated tube containing Krebs-Henseleit solution in an organ bath, maintained at 370C and one end was tied to an isometric force transducer with preset-tension of 0.5 g. The tracheal smooth muscles were equilibrated for about 60 minutes, during which time they were washed thrice with Krebs-Henseleit at 15 minutes interval. The tension of tracheal smooth muscle was recorded using a polygraph data acquisition system linked to isometric transducer that was connected to a recorder. Contractile activity of tracheal smooth muscle was recorded as dose response curves for both carbachol and histamine by adding doses of these spasmogens cumulatively (n=10). The dose responses were also recorded after incubation of tracheal smooth muscle with hydrogen peroxide (3 mM) for both carbachol and histamine (n=4). Further dose response curves for carbachol and histamine were recorded after prior incubating tracheal smooth muscle first with curcumin (30 nM) for 30 min followed by incubation with hydrogen peroxide (n=4). At the end of each experiment, the responses of carbachol and histamine were recorded and calculated as per cent of contractile response and their EC50 values were estimated and compared whether cucurmin has any effect on the H2O2 induced hyper responsiveness for carbachol and histamine spasmogenic activity. Data were expressed in mean ± SD and Tukey-Krammer test was applied after ANOVA for statistical significance at p<0.05.

Results - Mean EC50 (-log M) value obtained for carbachol was 3.63 x 10-8 with range from 2.63 x 10-8 to 5.88 x 10-8, which was shifted parallel to left significantly (p<0.01) in the presence of H2O2 with mean EC50 of carbachol standing at 7.08 x 10-9 with range 4.07 x 10-9 to 1.82 x 10-8 indicating H2O2 inducing hyper responsiveness of tracheal smooth muscle to carbachol that may due to oxidative damage. Prior curcumin incubation resulted almost restoring of carbachol mean EC50 (4.36 x 10-8) even in the presence of H2O2. However, histamine mean EC50 (5.37 x 10-7) obtained after histamine cumulative doses was not changed significantly (EC50, 9.54 x 10-7) even in the presence of H2O2 except for increased hyper response for histamine at threshold concentration. Curcumin incubation resulted significant (p<0.05) rightward parallel shift of histamine dose response curve with mean EC50 of histamine at 3.09 x 10 5 with range 1.82 x 10-5 to 1.07 x 10-4. This indicates curcumin can competitively blocks histamine induced contractions in tracheal smooth muscle.

Conclusions – Present investigation reveals that curcumin competitively block spasmogenic effects of carbachol and histamine. Thus, curcumin may be useful as spasmolytic agent in chronic inflammatory conditions like asthma, in which the airway smooth muscle is hyper responsive to spasmogens like carbachol and histamine pending in-vivo studies. [b][/b][b][/b][i][b][/i][i]