Role of adenylyl cyclase in reduced β-adrenoceptor-mediated vasorelaxation during maturation

Role of β-blockers in Preventing Heart Failure and Major Adverse Cardiac Events Post Myocardial Infarction

β-blockers have been widely utilized as a part of acute myocardial infarction (AMI) treatment for the past 40 years. Patients receiving β-adrenergic blockers for an extended period following myocardial infarction have a higher chance of surviving. Although many patients benefited from β-blockers, many do not, including those with myocardial infarction, left ventricle dysfunction, chronic pulmonary disease, and elderly people. In individuals with the post-acute coronary syndrome and normal left ventricular ejection fraction (LVEF), the appropriate duration of betablocker therapy is still unknown. There is also no time limit for those without angina and those who do not need β-blockers for arrhythmia or hypertension. Interestingly, β-blockers have been prescribed for more than four decades. The novel mechanism of action on cellular compartments has been found continually, which opens a new way for their potential application in cardiac failure and other cardiac events like post-myocardial infarction. Here, in this review, we studied β-blocker usage in these circumstances and the current recommendations for β-blocker use from clinical practice guidelines.

Release of vascular agonists from liposome-microbubble conjugate by ultrasound-mediated microbubble destruction: effect on vascular function

The endothelium is a single cell layer of the vessel wall and a key regulator of blood flow in vascular beds. Local and systemic pathologies have been associated with alterations in endothelial function. However, targeting the endothelium with vasoconstrictor or vasodilator drugs is often accompanied by systemic effects. Here, we evaluated a liposome-microbubble delivery system as a vascular hydrophilic agonist carrier. Phenylephrine (Phe) or acetylcholine (Ach)-loaded liposomes were conjugated to microbubbles. The drug release was triggered by ultrasound (US), and the vascular response was assessed in rat aortic rings using an isolated organ chamber. Aortic rings incubated with Phe-liposome-microbubble conjugate, exposed to US showed a marked contractile response (0.79 ± 0.04 g) compared to empty liposomes conjugated to microbubbles, aortic rings exposed only to US, and Phe-liposome-microbubble conjugate without US exposure that elicited a minimal or no response. Expressed as %, contractile responses were 85.24 ± 4.31% and 12.62 ± 3.23% for Phe-Chol-liposome-microbubble conjugate and empty Chol-liposome-microbubble conjugate exposed to US, respectively. Addition of 1 × 10^-5 M Ach to pre-contracted aortic rings decreased the contraction response from 1 to 0.21 g. The addition of Ach-liposome conjugate and exposure to US decreased the contraction response to 0.32 g. Additionally, the ED50 values for Phe and Ach released by US from liposome-microbubble conjugates were 3.6 × 10^-8 M ± 2.8 × 10^-9 M for Phe and 2.0 × 10^-8 M ± 1.8 × 10^-9 M. In conclusion, we evaluated a hybrid delivery system that consisted of loaded liposomes conjugated to microbubbles to deliver and release vascular agonists using UMMD.

Patchouli alcohol isolated from Pogostemon cablin mediates endothelium-independent vasorelaxation by blockade of Ca2+ channels in rat isolated thoracic aorta

ETHNOPHARMACOLOGICAL RELEVANCE

The aerial parts of Pogostemon cablin (Blanco) Benth. for the treatment of cardiodynia have been documented in Mingyi Bielu of late Han Dynasty, in addition to that the Ca²⁺ antagonized activities of P. cablin and its critically pharmacological ingredient patchouli alcohol (PA) were reported previously.

AIM OF THE STUDY

To investigate the relaxant effects of PA on rat isolated thoracic aortas and further explore its potential mechanisms of actions.

MATERIALS AND METHODS

The aortas with endothelium and without endothelium were prepared and suspended in the organ bath for isometric tension recordings. The responses to accumulative concentrations of PA in endothelium-intact (E + ) aortas with basal tension and in different treated aortas pre-contracted with potassium chloride (KCl) or phenylephrine (PHE) were observed; the effects of L-NAME and indomethacin in aortas with intact endothelium, and of L-NAME, propranolol, tetraethtylamine (TEA), 4-aminopyridine (4-AP), barium chloride (BaCl₂), glyburide in aortas with endothelial denudation on PA-produced vasorelaxation were assessed; the influences of PA on extracellular Ca²⁺ influx and intracellular Ca²⁺ release were measured in Ca²⁺-free medium. Finally, the abilities of PA to inhibit KCl- and PHE-induced contractions were compared to that of verapamil in E- aortas.

RESULTS

PA produced vasorelaxant effects in KCl- and PHE-precontracted E + aortas in a concentration-dependent manner, which had no statistically different from that in KCl- and PHE-precontracted E- aortas. PA (10 μM) significantly reduced KCl-induced contractions while PHE-induced contractions were significantly reduced by 100 μM of PA instead of 10 μM and 30 μM in aortas with endothelium. Pre-incubation of E + aortas with L-NAME as well as indomethacin and of E- aortas with L-NAME, propranolol, TEA, 4-AP, BaCl₂ and glyburide had no obvious effects on vasorelaxation of PA. In endothelium-removed aortas around Ca²⁺-free solution, PA remarkably lowered the contractions stimulated with Ca²⁺ and PHE, and application of ruthenium red and heparin further enhanced the abilities of PA to reduce PHE-caused contractions. In aortas without endothelium, 100 μM of PA markedly attenuated KCl-induced contractions but not affect PHE-induced contractions. Verapamil at the equal dose markedly attenuated KCl- and PHE-induced contractions, and the inhibitory effects on KCl-induced contractions were more forceful than that on PHE-induced contractions. In combined usage, the inhibitory effects on the contractions elicited by KCl were evidently weaker than that of verapamil alone and indifferently stronger than that of PA alone, and the inhibitory effects on the contractions elicited by PHE were evidently weaker than that of single verapamil but stronger than that of single PA.

CONCLUSION

PA may act as a Ca²⁺ antagonist to exert an intensively vasorelaxant effects through endothelium-independent pathway, and its mechanisms underlying the vasoactivities seem to be associated with the blockade of extracellular Ca²⁺ influx through VDCCs and ROCCs in vascular smooth muscle cells (VSMCs) membrane and intracellular Ca²⁺ releases through IP₃R- and RYR-mediated Ca²⁺ channels in sarcolemma.

Role of cyclic AMP in the eye with glaucoma

Glaucoma is characterized by a slow and progressive degeneration of the optic nerve, including retinal ganglion cell (RGC) axons in the optic nerve head (ONH), leading to visual impairment. Despite its high prevalence, the biological basis of glaucoma pathogenesis still is not yet fully understood, and the factors contributing to its progression are currently not well characterized. Intraocular pressure (IOP) is the only modifiable risk factor, and reduction of IOP is the standard treatment for glaucoma. However, lowering IOP itself is not always effective for preserving visual function in patients with primary open-angle glaucoma. The second messenger cyclic adenosine 3′,5′-monophosphate (cAMP) regulates numerous biological processes in the central nervous system including the retina and the optic nerve. Although recent studies revealed that cAMP generated by adenylyl cyclases (ACs) is important in regulating aqueous humor dynamics in ocular tissues, such as the ciliary body and trabecular meshwork, as well as cell death and growth in the retina and optic nerve, the functional role and significance of cAMP in glaucoma remain to be elucidated. In this review, we will discuss the functional role of cAMP in aqueous humor dynamics and IOP regulation, and review the current medications, which are related to the cAMP signaling pathway, for glaucoma treatment. Also, we will further focus on cAMP signaling in RGC growth and regeneration by soluble AC as well as ONH astrocytes by transmembrane ACs to understand its potential role in the pathogenesis of glaucoma neurodegeneration