Clarence Lim

Introduction. Renovascular hypertension is defined as a systolic blood pressure greater than 130 mmHg or a diastolic blood pressure greater than 80 mmHg with renovascular etiologies⁷. Renovascular hypertension accounts for approximately 3% of cases in unselected hypertensive patients⁷. Altered metabolism is a key cause in hypertension^5,6,8,9. Studies have shown hydrogen sulfide (HS), an endogenous substance known as a vasodilator, mediates the hypoxic response in coronary artery of pig hearts¹. Other studies show that reduction of HS upregulates the level of angiotensin II and oxidative stress enzymes while downregulating antioxidant enzymes^2,3. Further studies have shown that HS play a role in epigenetics in offspring⁴. These findings could suggest a potential medical therapy for renovascular hypertension. Methods. Five individual experiments were conducted to analyze the relationship between HS and the changes in hypertension activity. The first experiment determined whether HS mediates the hypoxic response by contracting the coronary arteries of pig hearts through a thromboxane A2 analog¹. The second experiment sought to determine the effect HS has on the level of angiotensin II by through radioimmunoassay². The third experiment took a further step to see what other oxidative-stress and antioxidant enzymes are affected by measuring enzyme activity in 2K1C and controlled rats³. The fourth experiment determined whether HS has any protective effect on offspring via measuring methylation of the AT1B gene⁴. The fifth experiment determined whether taurine, a sulfur-containing amino acid, has any effect on prehypertensive patients through a double-blind, randomized, placebo-controlled trial¹⁰. Results. The first experiment showed that hypoxia produces a biphasic vasomotor response, an initial transient contraction followed by a prolonged and prominent vasorelaxation¹. The second experiment showed an increase of angiotensin II in 2K1C rats². The third experiment showed increased levels of oxidative stress enzymes in 2K1C rats and reduced levels of SOD, an antioxidant enzyme³. The fourth experiment showed increased methylation of the AT1b gene with prenatal or postnatal administration with HS⁴. The fifth experiment showed a reduction of blood pressure and improvement of vasodilation in prehypertensive individuals with the taurine supplementation¹⁰. Conclusions. Studies have shown that there is a correlation between levels HS and the progression of renovascular hypertension, and by introducing HS, blood pressure can be reduced. As more investigations of HS and the mechanisms of renovascular hypertension are performed, new prognostic and therapeutic approaches can be conducted.

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2. Xue, H., Zhou, S., Xiao, L., Guo, Q., Liu, S., Wu, Y. Hydrogen Sulfide Improves the Endothelial Dysfunction in Renovascular Hypertensive Rats. Physiol. Res. 2015;64(1):663-672.
3. Guo, , Feng, X., Xue, H., Teng, X., Jin, S., Duan, X., Xiao. L., Wu, Y. Maternal Renovascular Hypertensive Rats Treatment with Hydrogen Sulfide Increased Methylation of AT1b Gene in Offspring. American Journal of Hypertension. 2017;30(12):1220-1227.
4. Liu, S., Duan, X., Jin, S., Teng, X., Xiao, L., Xue, H., Wu, Y. Hydrogen Sulfide Improves Mycorcardial Remodeling via Downregulated Angiotensin II/AT1R Pathway in Renovascular Hypertensive Rats. American Journal of Hypertension. 2017;30(1):67-74.
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