The effects of tapering with and without ethanolic extract of Nigella sativa on Hypoxia Inducible Factor-1α and exercise-induced bronchial changes

Background and Aim: Tapering with herbal remedies may decrease the time for soft tissue injury recovery. In the present study, we investigated the effect of ethanolic extract of Nigella Sativa (NS) consumption during the taper period on hypoxia-inducible factor-1α and exercise-induced bronchial changes. Methods: A total of 60 male Wistar rats (five weeks old) were randomized to one of two groups: control (n=10) or exercise training (n=50). After 6 weeks of Incremental Interval Training (IIT) (70 to 35 m/min) the exercise training group were randomized into 4 groups of taper (50 to 25 m/min): 2 weeks taper without NS (I), 2 weeks taper with NS (II), 3 weeks taper without NS (III), 3 weeks taper with NS (IV). The IIT and taper program was performed on a treadmill with exercise performed at intervals. The taper groups with NS, received daily ethanolic extract of Nigella sativa (500 mg/kg) by gavage. Finally, animals were euthanized and the right lobe of the lung was removed. Tissues were fixed in 10% formalin, embedded in paraffin, and then manually sectioned with a microtome to obtain 5‒6 μm-thick paraffin sections. The sections were then stained with hematoxylin and eosin (H&E) to be examined histologically and histometrically. HIF-1α protein from the left lobe of the lung was also measured using a commercially-available ELISA kit. Data analysis was performed using two-way ANOVA and LSD test at P<0.05.   Results: Group II were heavier than the other groups (P≤0.05). Groups not receiving NS showed a significant increase in HIF-1a compared to the control group in the second (P = 0.001) and third (P = 0.007) weeks of tapering. Groups with NS showed a significant decrease in hypoxia induce factor (P = 0.001) compared with the IIT group. The diameter of bronchi advents in taper groups with NS significantly decreased (p=0.001) compared with the IIT group, with the greatest reduction (55.23%) reported in the 3-week taper with NS group. The histological images of the 3-week taper with NS group had better structural integrity than the other groups.  Conclusion: The use of ethanolic extracts of NS with tapering seems to prevent negative apoptosis of lung parenchyma, with a decrease of HIF-1α, and minimized exercise-induced bronchoconstriction by improving the bronchi structure.