Direct regulation of vascular smooth muscle contraction by mastoparan-7

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

Effectiveness of Scutellaria baicalensis Georgi root in pregnancy-related diseases: A review

The root of Scutellaria baicalensis Georgi, also called Huangqin, is frequently used in traditional Chinese medicine. In ancient China, S. baicalensis root was used to clear heat, protect the fetus, and avoid a miscarriage for thousands of years. In modern times, pregnancy-related diseases can seriously affect maternal and fetal health, but few systematic studies have explored the mechanisms and potential targets of S. baicalensis root in the treatment of pregnancy-related diseases. Flavonoids (baicalein, wogonin and oroxylin A) and flavonoid glycosides (baicalin and wogonoside) are the main chemical components in the root of S. baicalensis. This study presents the current understanding of the major chemical components in the root of S. baicalensis, focusing on their traditional uses, potential therapeutic effects and ethnopharmacological relevance to pregnancy-related disorders. The mechanisms, potential targets and experimental models of S. baicalensis root for ameliorating pregnancy-related diseases, such as recurrent spontaneous abortion, preeclampsia, preterm birth, fetal growth restriction and gestational diabetes mellitus, are highlighted.

Effect of reperfusion on vascular smooth muscle reactivity in three contraction models

BACKGROUND

Ischemia and reperfusion remain inseparable elements of numerous medical procedures such as by-pass surgery, organ transplantation or other cardiology and intervention radiology. The contraction of the smooth muscle of the vessel is considered to be one of the basic components leading to impaired perfusion, an increase in the oxygen deficit of the endothelium of the vessel, and subsequently also to tissues vascularized by the vessel. Main aim of this study was to evaluate the effect of ischemia and reperfusion on vascular smooth muscle cells stimulated pharmacologically with mastoparan-7 (direct G-protein activator) in comparison to stimulation of G-protein coupled receptor agonist - phenylephrine, and direct calcium channel activator - Bay K8644.

MATERIAL AND METHODS

Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow.

RESULTS

Concentration-response curves obtained for phenylephrine, mastoparan-7 and Bay K8644 presented a sigmoidal relation. Ischemia induced hyporreactivity of vessels, whereas during reperfusion the significant time related hyperreactivity for phenylephrine and mastoparan-7 only but not for Bay K8644. These reactions were secondary to the modulation of calcium influx from intra- and extracellular calcium stores.

CONCLUSIONS

Results of our experiments suggest that mastoparan-7 significantly induces contraction of vascular smooth muscle cells not only for controls but in the presence of ischemia and reperfusion too. Potential therapeutic applications of the observed reactions are important. They may include regenerative processes within the nervous system, studies on the improvement of blood flow within the microcirculation, or antimicrobial activity. Modulation of the G protein-phospholipase C response may also be an interesting point of action of future drugs modifying the response to stimulation during ischemia in particular, such activities could take place during the transport of organs for transplantation.

The Modulatory Effect of Ischemia and Reperfusion on Arginine Vasopressin-Induced Arterial Reactions

Aim of the Study. The purpose of this study was to investigate the impact of ischemia and reperfusion on the resistance of arteries to AVP (arginine vasopressin), with a particular emphasis on the role of smooth muscle cells in the action of vasopressin receptors and the role of the cGMP-associated signalling pathway. Materials and Methods. Experiment was performed on the perfunded tail arteries from male Wistar rats. The constriction triggered by AVP after 30 minutes of ischemia and 30 and 90 minutes of reperfusion was analysed. Analogous experiments were also carried out in the presence of 8Br-cGMP. Results. Ischemia reduces and reperfusion increases in a time-dependent manner the arterial reaction to AVP. The presence of 8Br-cGMP causes a significant decrease of arterial reactivity under study conditions. Conclusions. Ischemia and reperfusion modulate arterial contraction triggered by AVP. The effect of 8Br-cGMP on reactions, induced by AVP after ischemia and reperfusion, indicates that signalling pathway associated with nitric oxide (NO) and cGMP regulates the tension of the vascular smooth muscle cells.

Cyclosporine-A, but not tacrolimus significantly increases reactivity of vascular smooth muscle cells

BACKGROUND

Application of cyclosporine-A (CsA) or tacrolimus is associated with numerous side effects. One of the main reasons for restricting usage of CsA is hypertension. In tacrolimus treated subjects the frequency of these phenomena is significantly lower. The known molecular mechanism of action of tacrolimus and cyclosporine-A seems to be the same, thus we decided to compare modulatory effect of drugs on vascular smooth muscle contractility.

METHODS

Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force was measured by increased degree of perfusion pressure with a constant flow rate.

RESULTS

Concentration-response curves for agonist in the presence CsA were significantly shifted to the left with increase in maximal responses. This effect was due to increased calcium influx from extracellular calcium stores whereas there were no significant changes in calcium influx in the presence of tacrolimus; concentration-response curve was comparable to controls.

CONCLUSION

Our results strongly support the idea that main difference between effects on smooth muscle contractility of calcineurin-dependent immunosuppressants: CsA and tacrolimus is related to the different level of extracellular calcium influx to the cytoplasm. The elucidation of these mechanisms may permit the identification of new therapeutic strategies against CsA-induced hypertension.

Effect of pertussis toxin on calcium influx in three contraction models

Pertussis toxin (PTX) blocks G protein activation and inhibits signal transmission from the activated receptor to effectors that are specific for the G protein-coupled receptor. The aim of the present study was to evaluate the effect of PTX on vascular smooth muscle cells that were stimulated pharmacologically with phenylephrine (α-adrenoceptor agonist), mastoparan-7 (direct G-protein activator) and Bay K8644 (direct calcium channel activator). The changes in perfusion pressure that were proportional to the degree of phenylephrine-induced constriction of rat tail arteries were assessed. Concentration-response curves (CRCs) that were obtained for phenylephrine, mastoparan-7 and Bay K8644 presented a sigmoidal association. A significantly reduced calcium influx to the cytoplasm in the presence of mastoparan-7 resulted in a significant rightward shift of the CRCs with a significant reduction in maximal responses. The presence of PTX did not change mastoparan-7 and Bay K8644-induced contraction, whereas the significant inhibition of phenylephrine-induced contraction was found. The results of the experiments indicated that PTX significantly inhibited phenylephrine-induced contraction of vascular smooth muscle cells by inhibition of calcium influx from the intra- and extracellular calcium space. PTX did not change the smooth muscle contraction that was induced by mastoparan-7 and Bay K8644. The predominant effect of mastoparan-7 may be associated with other binding sites as compared to the G-protein or PTX may bind to other sites than mastoparan-7.