لخّصلي

Alpha receptors, classified into subtypes ?1, ?2, and ?3, are integral components of the adrenergic signaling pathways that modulate various physiological functions.The implications for therapeutic strategies in conditions such as hypertension and prostate diseases are substantial, as non-selective ?1 antagonists have exhibited adverse cardiac effects in clinical settings, further underscoring the necessity for a nuanced approach in targeting adrenergic signaling pathways in clinical practice ().Upon stimulation by norepinephrine and epinephrine, the activation of these receptors leads to the phosphorylation of extracellular signal-regulated kinase (ERK) and endothelial nitric oxide synthase (eNOS), which are essential signals in promoting cellular processes such as DNA synthesis and vascular tone regulation.

Alpha receptors, classified into subtypes α1, α2, and α3, are integral components of the adrenergic signaling pathways that modulate various physiological functions. This section focuses on the sites of alpha receptors, delineating their distribution across different tissues and their functional implications. Specifically, the α1 subtype receptors are predominantly found in vascular tissues, including smooth muscle cells and endothelial cells, where they play crucial roles in vasoconstriction and endothelial regulation.

Recent research has highlighted the presence of α1B adrenergic receptors in human epicardial coronary artery endothelial cells (ECs) as a particularly significant finding. demonstrated that α1B is the predominant and functional subtype expressed in these cells, accounting for over 90% of α1-mRNA. Upon stimulation by norepinephrine and epinephrine, the activation of these receptors leads to the phosphorylation of extracellular signal-regulated kinase (ERK) and endothelial nitric oxide synthase (eNOS), which are essential signals in promoting cellular processes such as DNA synthesis and vascular tone regulation. Notably, the high density of α1B receptor expression in coronary ECs, which is approximately twice that of the α1D subtype found in smooth muscle cells (SMCs), indicates a potential mechanism for the counter-regulatory vasodilation response in the coronary arteries. This distinction emphasizes the role of the α1B subtype in adaptive processes, particularly under pathological conditions where endothelial function may be compromised, suggesting a vital role in maintaining coronary artery integrity ().

In contrast, the α1D subtype, predominantly located in human coronary SMCs, mediates vasoconstriction but shows limited effect under normal conditions. This differential expression leads to a complex interaction where the loss of the α1B receptor in ECs may contribute to heightened vasoconstriction via the α1D mechanism in scenarios where the endothelium is disrupted. Understanding the distinct roles and distribution of these receptors is critical, particularly as pharmacological agents targeting α1 receptors can yield different cardiovascular outcomes based on their subtype selectivity. The implications for therapeutic strategies in conditions such as hypertension and prostate diseases are substantial, as non-selective α1 antagonists have exhibited adverse cardiac effects in clinical settings, further underscoring the necessity for a nuanced approach in targeting adrenergic signaling pathways in clinical practice ().