Mechanism underlying the vasodilation induced by diosmetin in porcine coronary artery

Cilostazol induces vasorelaxation through the activation of the eNOS/NO/cGMP pathway, prostanoids, AMPK, PKC, potassium channels, and calcium channels

OBJECTIVE

This study aimed to investigate vasoactive effect mechanisms of cilostazol in rat thoracic aorta.

MATERIALS AND METHODS

The vessel rings prepared from the thoracic aortas of the male rats were placed in the chambers of the isolated tissue bath system. The resting tone was adjusted to 1 g. Following the equilibration phase, potassium chloride or phenylephrine was used to contract the vessel rings. When achieving a steady contraction, cilostazol was applied cumulatively (10-8-10-4 M). In the presence of potassium channel blockers or signaling pathway inhibitors, the same experimental procedure was performed.

RESULTS

Cilostazol exhibited a significant vasorelaxant effect in a concentration-dependent manner (pD2: 5.94 ± 0.94) (p < .001). The vasorelaxant effect level of cilostazol was significantly reduced by the endothelial nitric oxide synthase inhibitor L-NAME (10-4 M), soluble guanylate cyclase inhibitor methylene blue (10 µM), cyclooxygenase 1/2 inhibitor indomethacin (5 µM), adenosine monophosphate-activated protein kinase inhibitor compound C (10 µM), non-selective potassium channel blocker tetraethylammonium chloride (10 mM), large-conductance calcium-activated potassium channel blocker iberiotoxin (20 nM), voltage-gated potassium channel blocker 4-Aminopyridine (1 mM), and inward-rectifier potassium channel blocker BaCl2 (30 µM) (p < .001). Moreover, incubation of cilostazol (10-4 M) significantly reduced caffeine (10 mM), cyclopiazonic acid (10 µM), and phorbol 12-myristate 13-acetate-induced (100 µM) vascular contractions (p < .001).

CONCLUSIONS

In the rat thoracic aorta, the vasodilator action level of cilostazol is quite noticeable. The vasorelaxant effects of cilostazol are mediated by the eNOS/NO/cGMP pathway, prostanoids, AMPK pathway, PKC, potassium channels, and calcium channels.

The Antioxidative Effects of Flavones in Hypertensive Disease

Hypertension is the leading remediable risk factor for cardiovascular morbidity and mortality in the United States. Excess dietary salt consumption, which is a catalyst of hypertension, initiates an inflammatory cascade via activation of antigen-presenting cells (APCs). This pro-inflammatory response is driven primarily by sodium ions (Na+) transporting into APCs by the epithelial sodium channel (ENaC) and subsequent NADPH oxidase activation, leading to high levels of oxidative stress. Oxidative stress, a well-known catalyst for hypertension-related illness development, disturbs redox homeostasis, which ultimately promotes lipid peroxidation, isolevuglandin production and an inflammatory response. Natural medicinal compounds derived from organic materials that are characterized by their anti-inflammatory, anti-oxidative, and anti-mutagenic properties have recently gained traction amongst the pharmacology community due to their therapeutic effects. Flavonoids, a natural phenolic compound, have these therapeutic benefits and can potentially serve as anti-hypertensives. Flavones are a type of flavonoid that have increased anti-inflammatory effects that may allow them to act as therapeutic agents for hypertension, including diosmetin, which is able to induce significant arterial vasodilation in several different animal models. This review will focus on the activity of flavones to illuminate potential preventative and potential therapeutic mechanisms against hypertension.

Antioxidant Flavonoid Diosmetin Is Cardioprotective in a Rat Model of Myocardial Infarction Induced by Beta 1-Adrenergic Receptors Activation

Myocardial infarction (MI) is a common and life-threatening manifestation of ischemic heart diseases (IHD). The most important risk factor for MI is hypertension. Natural products from medicinal plants have gained considerable attention globally due to their preventive and therapeutic effects. Flavonoids have been found to be efficacious in ischemic heart diseases (IHD) by alleviating oxidative stress and beta-1 adrenergic activation, but the mechanistic link is not clear. We hypothesized that antioxidant flavonoid diosmetin is cardioprotective in a rat model of MI induced by beta 1-adrenergic receptor activation. To test this hypothesis, we evaluated the cardioprotective potential of diosmetin on isoproterenol-induced MI in rats by performing lead II electrocardiography (ECG), cardiac biomarkers including troponin I (cTnI) and creatinine phosphokinase (CPK), CK-myocardial band, (CK-MB), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), and aspartate aminotranferase (AST) by using biolyzer 100, as well as histopathological analysis. We found that diosmetin (1 and 3 mg/kg) attenuated isoproterenol-induced elevation in the T-wave and deep Q-wave on the ECG, as well as heart-to-body weight ratio and infarction size. In addition, pretreatment with diosmetin attenuated the isoproterenol-induced increase in serum troponin I. These results demonstrate that flavonoid diosmetin may provide therapeutic benefit in myocardial infarction.

ELABELA RELAXES RAT PULMONARY ARTERY AND TRACHEA VIA BKCa, KV, and KATP CHANNELS

OBJECTIVE

Elabela is a newly discovered peptide hormone. This study aimed to determine the functional effects and mechanisms of action of elabela in rat pulmonary artery and trachea.

MATERIALS AND METHODS

Vascular rings isolated from the pulmonary arteries of male Wistar Albino rats were placed in chambers in the isolated tissue bath system. The resting tension was set to 1g. After the equilibration period, the pulmonary artery rings were contracted with 10^-6M phenylephrine. Once a stable contraction was achieved, elabela was applied cumulatively (10^-10-10^-6M) to the vascular rings. To determine the vasoactive effect mechanisms of elabela, the specified experimental protocol was repeated after the incubation of signaling pathway inhibitors and potassium channel blockers. The effect and mechanisms of action of elabela on tracheal smooth muscle were also determined by a similar protocol.

RESULTS

Elabela exhibited a concentration-dependent relaxation in the precontracted rat pulmonary artery rings (p<.001). Maximal relaxation level was 83% (pEC₅₀: 7.947 CI95(7.824-8.069)). Removal of the endothelium, indomethacin incubation, and dideoxyadenosine incubation significantly decreased the vasorelaxant effect levels of elabela (p<.001). Elabela-induced vasorelaxation levels were significantly reduced after iberiotoxin, glyburide, and 4-Aminopyridine administrations (p<.001). L-NAME, methylene blue, apamin, TRAM-34, anandamide, and BaCl₂ administrations did not cause a significant change in the vasorelaxant effect level of elabela (p=1.000). Elabela showed a relaxing effect on precontracted tracheal rings (p<.001). Maximal relaxation level was 73% (pEC₅₀: 6.978 CI95(6.791-7.153)). The relaxant effect of elabela on tracheal smooth muscle was decreased significantly after indomethacin, dideoxyadenosine, iberiotoxin, glyburide, and 4-Aminopyridine incubations (p<.001).

CONCLUSIONS

Elabela exerted a prominent relaxant effect in the rat pulmonary artery and trachea. Intact endothelium, prostaglandins, cAMP signaling pathway, and potassium channels (BK_Ca, K_V, and K_ATP channels) are involved in the vasorelaxant effect of elabela. Prostaglandins, cAMP signaling pathway, BK_Ca channels, K_V channels, and K_ATP channels also contribute to elabela-induced tracheal smooth muscle relaxant effect.

Investigation into the Antihypertensive Effects of Diosmetin and Its Underlying Vascular Mechanisms Using Rat Model

Objective: Diosmetin is a flavonoid that is found in many important medicinal plants that have antihypertensive therapeutic potential. Diosmetin has been shown to have antiplatelet, anti-inflammatory and antioxidant properties, which suggests that it could be a potential candidate for use in antihypertensive therapy. Methods: In vivo and in vitro methods were used for our investigation into the antihypertensive effects of diosmetin. Results: Diosmetin significantly decreased the mean arterial pressure (MAP). The effects of diosmetin on the MAP and heart rate were more pronounced in hypertensive rats. To explore the involvement of the muscarinic receptors-linked NO pathway, Nω-nitro-L-arginine methyl ester (L-NAME) and atropine were pre-administered in vivo. The pretreatment with L-NAME did not significantly change the effects of diosmetin on the MAP by excluding the involvement of NO. Unlike L-NAME, the atropine pretreatment reduced the effects of diosmetin on the MAP, which demonstrated the role of the muscarinic receptors. In the in vitro study, diosmetin at lower concentrations produced endothelium-dependent and -independent (at higher concentrations) vasorelaxation, which was attenuated significantly by the presence of atropine and indomethacin but not L-NAME. Diosmetin was also tested for high K+-induced contractions. Diosmetin induced significant relaxation (similar to verapamil), which indicated its Ca2+ antagonistic effects. This was further confirmed by diosmetin shifting the CaCl₂ CRCs toward the right due to its suppression of the maximum response. Diosmetin also suppressed phenylephrine peak formation, which indicated its antagonist effects on the release of Ca2+. Moreover, BaCl₂ significantly inhibited the effects of diosmetin, followed by 4-AP and TEA, which suggested that the K+ channels had a role as well. Conclusions: The obtained data showed the Ca2+ channel antagonism, potassium channel activation and antimuscarinic receptor-linked vasodilatory effects of diosmetin, which demonstrated its antihypertensive potential.

Diosmetin Affects Gene Expression on Human Lung Adenocarcinoma Cells

Objective

This study was aimed at investigating the effects of diosmetin (a natural flavonoid) on the gene expression of human lung adenocarcinoma (LUAD) cells.

Methods

HCC827 and A549 cells were used. MTT and colony formation assay were used to investigate the effects of diosmetin on cell proliferation and colony forming activity. The expression of mRNA, microRNA, and lncRNA in HCC827 and A549 cell lines after diosmetin treatment was measured using DNA microarray, microRNA chromatin immunoprecipitation assay (ChIP), and long noncoding RNA (lncRNA) ChIP. Part of the results were cross-validated by quantitative reverse transcription PCR (RT-qPCR), while some others were analyzed using bioinformatic tools.

Results

Diosmetin inhibited proliferation and colony formation of HCC827 and A549 cells. Investigation on gene expression profiles of A549 and HCC827 cells revealed that compared with the control group, diosmetin can up- or downregulated the expression of mRNAs, microRNAs, and lncRNAs. The top three candidates in each RNA category were cross-validated by RT-qPCR, from which single peaks were observed in the melt curves, showing a great specificity. After a comprehensive selection of the results from the mRNA ChIP, we performed GO and KEGG functional clustering analyses on the differentially expressed genes.

Conclusion

Diosmetin treatment induced gene expression of A549 and HCC827 cells. Our results will provide guidance for development of new diagnostic and therapeutic targets.

The antihypertensive potential of flavonoids from Chinese Herbal Medicine: A review

With the coming of the era of the aging population, hypertension has become a global health burden to be dealt with. Although there are multiple drugs and procedures to control the symptoms of hypertension, the management of it is still a long-term process, and the side effects of conventional drugs pose a burden on patients. Flavonoids, common compounds found in fruits and vegetables as secondary metabolites, are active components in Chinese Herbal Medicine. The flavonoids are proved to have cardiovascular benefits based on a plethora of animal experiments over the last decade. Thus, the flavonoids or flavonoid-rich plant extracts endowed with anti-hypertension activities and probable mechanisms were reviewed. It has been found that flavonoids may affect blood pressure in various ways. Moreover, despite the substantial evidence of the potential for flavonoids in the control of hypertension, it is not sufficient to support the clinical application of flavonoids as an adjuvant or core drug. So the synergistic effects of flavonoids with other drugs, pharmacokinetic studies, clinical trials and the safety of flavonoids are also incorporated in the discussion. It is believed that more breakthrough studies are needed. Overall, this review may shed some new light on the explicit recognition of the mechanisms of anti-hypertension actions of flavonoids, pointing out the limitations of relevant research at the current stage and the aspects that should be strengthened in future researches.

Diosmetin Ameliorates Vascular Dysfunction and Remodeling by Modulation of Nrf2/HO-1 and p-JNK/p-NF-κB Expression in Hypertensive Rats

Diosmetin is a citrus flavonoid that has antioxidant and anti-inflammatory effects. This study examined the effect of diosmetin on blood pressure and vascular alterations and its underlying mechanisms in experimentally hypertensive rats. Male Sprague rats were administered Nω-nitro-l-arginine methyl ester L-NAME for five weeks and were given diosmetin at doses of 20 or 40 mg/kg or captopril (5 mg/kg) for two weeks. Diosmetin alleviated hypertension, improved endothelial dysfunction, and suppressed the overactivity of sympathetic nerve-mediated vasoconstriction in aorta and mesentery hypertensive rats (p < 0.05). Increases in plasma and aortic tissue malondialdehyde (MDA) and carotid superoxide generations and reductions of plasma superoxide dismutase, catalase, and nitric oxide in hypertensive rats were ameliorated by diosmetin (p < 0.05). Diosmetin increased the protein expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) in hypertensive rats. Furthermore, diosmetin mitigated hypertrophy and collagen accumulation of the aortic wall in L-NAME rats. It exhibited an anti-inflammatory effect by reducing interleukin-6 (IL-6) accumulation and by overexpressing the phospho-c-Jun N-terminal kinases (p-JNK) and the phospho-nuclear factor-kappaB (p-NF-κB) proteins in the aorta (p < 0.05). Captopril was a positive control substance and had similar effects to diosmetin. In summary, diosmetin reduced blood pressure and alleviated vascular abnormalities in L-NAME-treated rats. These effects might be related to antioxidant and anti-inflammatory effects as well as to the modulation of the expression of the Nrf2/HO1 and p-JNK/NF-κB proteins.