Khaidar Gufranov

Background/Objectives: Molecular hydrogen (H₂), a natural antioxidant, can selectively reduce hydroxyl radicals and peroxynitrite without affecting signaling molecules such as H₂O₂ and NO. In addition, H₂ can inhibit the synthesis of inflammatory cytokines. Human and animal studies have shown that the inhalation of H₂ has a hypotensive effect. In this context, the aim of the present work was to study the effect of H₂ on the baroreflex regulation of blood pressure in rats with experimental monocrotaline-induced pulmonary hypertension (MCT) in vivo and the effects of H₂ on the reactivity of isolated rat aorta with MCT pulmonary hypertension to α₁-adrenoceptor agonists in vitro. Methods: Experiments were performed on male Wistar rats with MCT pulmonary hypertension; animals were placed in plastic chambers aerated with atmospheric air at a rate of 4 L/min with O₂ and CO₂ control. Cages with the rats of the MCT-H₂ and Control-H₂ groups were ventilated with air containing 4% H₂ twice daily for 2 h each. The MCT-Air and Control-Air groups breathed only atmospheric air. The duration of the experiment was 21 days. On day 20, blood pressure and heart rate (HR) were measured in awake animals and the baroreflex response to phenylephrine (PE) and nitroprusside (NP) was tested. In in vitro experiments, we studied the effect of adding H₂ to the perfusion solution on the responsiveness of isolated aortic preparations from MCT and control rats to the α₁-adrenoceptor agonist PE and the vasodilators NP and Acetylcholine. Results: When the effect of H₂ on the baroreflex response to NP (4.5 μg/kg) was examined in awake rats, the increase in HR was 73.1 ± 16.7 beats/min in the MCT-Air group and 48.1 ± 10.2 beats/min in the MCT-H₂ group (p < 0.01). In the Control-H₂ and Control-Air groups, there was a trend towards a lower HR in the Control-H₂ group, but the differences were not significant. No differences in HR response to PE administration were found between any of the experimental groups. Experiments on isolated aortic preparations from MCT rats showed that the addition of H₂ to the perfusion medium resulted in a 30% reduction in the maximal response to PE compared with the MCT group without hydrogen (p < 0.01), and the potency of PE (EC₅₀) decreased threefold (p < 0.05). There was a decrease in tryptase secretion, indicating an anti-inflammatory effect of H₂. Conclusions. The results demonstrate that H₂ inhalation was associated with an attenuated heart rate response to nitroprusside-induced hypotension and reduced vascular reactivity to phenylephrine in rats with pulmonary hypertension.

Hydrogen is known to have selective antioxidant properties. It binds highly reactive hydroxyl radicals. The pathogenesis of the monocrotaline animal model of pulmonary hypertension is associated with oxidative stress and leads to all the symptoms of pulmonary hypertension (PH) and interstitial lung disease (ILD) associated with hypertension.The aim of this work was to study the effect of 4% hydrogen inhalations on the symptoms of PH and ILD in rats.Methods. To model monocrotaline-induced pulmonary hypertension (MCT-PH), two groups of animals received a single subcutaneous injection of monocrotaline (MCT) on day 1. The control group was injected subcutaneously with MCT solvent only. The animals receiving MCT were further divided into 2 subgroups. Subgroup 1 rats breathed room air and subgroup 2 rats breathed a mixture of room air and 4% hydrogen. The regular inhalations continued until day 21. On day 21, hemodynamic parameters were measured under urethane anesthesia, the heart and its components and the lungs were weighed, and lung tissue was preserved for morphological study.Results. The inhalation had no effect on the main cardiovascular symptoms of PH, but a positive effect on the state of the connective tissue of the lungs affected by PH was shown. The mast cell response was reduced both quantitatively and functionally. There was a decrease in tryptase expression by mast cells, with predominance of the forms without signs of degranulation. TGF-β secretion was also significantly reduced and visualized by immunopositive cells in alveolar cellular structures and vessel walls.Conclusion. Inhalation of 4% hydrogen reduces inflammation and fibrosis of lung tissue during the development of MCT-PH.

Hydrogen has been shown to exhibit selective antioxidant properties against hydroxyl radicals, and exerts antioxidant and anti-inflammatory effects. The monocrotaline-induced model of pulmonary hypertension is suitable for studying substances with antioxidant activity because oxidative stress is induced by monocrotaline. On day 1, male Wistar rats were subcutaneously injected with a water–alcohol solution of monocrotaline or a control with an only water–alcohol solution. One group of monocrotaline-injected animals was placed in a plastic box that was constantly ventilated with atmospheric air containing 4% of molecular hydrogen, and the two groups of rats, injected with monocrotaline or vehicle, were placed in boxes ventilated with atmospheric air. After 21 days, hemodynamic parameters were measured under urethane narcosis. The results showed that, although hydrogen inhalation had no effect on the main markers of pulmonary hypertension induced by monocrotaline injection, there was a reduction in systemic blood pressure due to its systolic component, and a decrease in TGF-β expression, as well as a reduction in tryptase-containing mast cells.