Pharmacological analysis of the increases in heart rate and diastolic blood pressure produced by (S)-isometheptene and (R)-isometheptene in pithed rats

Identification of Potential Lead Compounds Targeting Novel Druggable Cavity of SARS-CoV-2 Spike Trimer by Molecular Dynamics Simulations

The global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become an urgent public health problem. Spike (S) protein mediates the fusion between the virus and the host cell membranes, consequently emerging as an important target of drug design. The lack of comparisons of in situ full-length S homotrimer structures in different states hinders understanding the structures and revealing the function, thereby limiting the discovery and development of therapeutic agents. Here, the steady-state structures of the in situ full-length S trimer in closed and open states (Sclosed and Sopen) were modeled with the constraints of density maps, associated with the analysis of the dynamic structural differences. Subsequently, we identified various regions with structure and property differences as potential binding pockets for ligands that promote the formation of inactive trimeric protein complexes. By using virtual screening strategy and a newly defined druggable cavity, five ligands were screened with potential bioactivities. Then molecular dynamic (MD) simulations were performed on apo protein structures and ligand bound complexes to reveal the conformational changes upon ligand binding. Our simulation results revealed that sulforaphane (SFN), which has the best binding affinity, could inhibit the conformational changes of S homotrimer that would occur during the viral membrane fusion. Our results could aid in the understanding of the regulation mechanism of S trimer aggregation and the structure-activity relationship, facilitating the development of potential antiviral agents.

Pharmacological Profile of the Purinergic P2Y Receptors That Modulate, in Response to ADPβS, the Vasodepressor Sensory CGRPergic Outflow in Pithed Rats

Calcitonin gene-related peptide (CGRP), an endogenous neuropeptide released from perivascular sensory nerves, exerts a powerful vasodilatation. Interestingly, adenosine triphosphate (ATP) stimulates the release of CGRP by activation of prejunctional P2X_2/3 receptors, and adenosine 5'-O-2-thiodiphosphate (ADPβS), a stable adenosine diphosphate (ADP) analogue, produces vasodilator/vasodepressor responses by endothelial P2Y₁ receptors. Since the role of ADP in the prejunctional modulation of the vasodepressor sensory CGRPergic drive and the receptors involved remain unknown, this study investigated whether ADPβS inhibits this CGRPergic drive. Accordingly, 132 male Wistar rats were pithed and subsequently divided into two sets. In set 1, ADPβS (5.6 and 10 µg/kg·min) inhibited the vasodepressor CGRPergic responses by electrical stimulation of the spinal T₉-T₁₂ segment. This inhibition by ADPβS (5.6 µg/kg·min) was reverted after i.v. administration of the purinergic antagonists MRS2500 (300 µg/kg; P2Y₁) or MRS2211 (3000 µg/kg; P2Y₁₃), but not by PSB0739 (300 µg/kg; P2Y₁₂), MRS2211 (1000 µg/kg; P2Y₁₃) or the K_ATP blocker glibenclamide (20 mg/kg). In set 2, ADPβS (5.6 µg/kg·min) failed to modify the vasodepressor responses to exogenous α-CGRP. These results suggest that ADPβS inhibits CGRP release in perivascular sensory nerves. This inhibition, apparently unrelated to activation of ATP-sensitive K⁺ channels, involves P2Y₁ and probably P2Y₁₃, but not P2Y₁₂ receptors.

A molecularly imprinted gel photonic crystal sensor for recognition of chiral amino acids

A new type of photonic crystal gel molecularly imprinted sensor (MIPHs) was synthesized for the visible chiral recognition of amino acids. The color of MIPHs was changed from green to red when it exposured to various l-pyroglutamic acid concentration (0.05-1.0mmoL/L). Thanks to sensitive reflectance of photonic crystal and high selectivity of MIPs, the constructed MIPHs exhibited good performance towards l-pyroglutamic acid in terms of fast response time (3 min) and low detection limit (LOD) (2.4 μmol/L). Besides, MIPHs was found to have good selectivity toward l-pyroglutamic acid in the presence of interference group with similar structures such as d-pyroglutamic acid, l-tryptophan, l-phenylalanine, and l-proline. In light of these findings, the MIPHs can be used for highly selective recognition of l-pyroglutamic acid. It is expected that our work is able to provide a new roadmap for the chiral identification and separation of amino acids.

The role of purinergic P2Y12 and P2Y13 receptors in ADPβS-induced inhibition of the cardioaccelerator sympathetic drive in pithed rats

ATP is a cotransmitter released with other neurotransmitters from sympathetic nerves, where it stimulates purinergic receptors. Purinergic adenosine P₁ receptors (coupled to G_i/o proteins) produce sympatho-inhibition in several autonomic effectors by prejunctional inhibition of neurotransmitter release. Similarly, signalling through P2Y₁₂ and P2Y₁₃ receptors coupled to G_i/o proteins is initiated by the ATP breakdown product ADP. Hence, this study has pharmacologically investigated a possible role of ADP-induced inhibition of the cardioaccelerator sympathetic drive in pithed rats, using a stable ADP analogue (ADPβS) and selective antagonists for the purinergic P2Y₁, P2Y₁₂ and P2Y₁₃ receptors. Accordingly, male Wistar rats were pithed and: (i) pretreated i.v. with gallamine (25 mg/kg) and desipramine (50 μg/kg) for preganglionic spinal (C₇-T₁) stimulation of the cardioaccelerator sympathetic drive (n = 78); or (ii) prepared for receiving i.v. injections of exogenous noradrenaline (n = 12). The i.v. continuous infusions of ADPβS (10 and 30 μg/kg/min) dose-dependently inhibited the tachycardic responses to electrical sympathetic stimulation, but not those to exogenous noradrenaline. The cardiac sympatho-inhibition produced by 30 μg/kg/min ADPβS was (after i.v. administration of compounds) (i) unchanged by 1-ml/kg bidistilled water or 300-μg/kg MRS 2500 (P2Y₁ receptor antagonist), (ii) abolished by 300-μg/kg PSB 0739 (P2Y₁₂ receptor antagonist) and (iii) partially blocked by 3000-μg/kg MRS 2211 (P2Y₁₃ receptor antagonist). Our results suggest that ADPβS induces a cardiac sympatho-inhibition that mainly involves the P2Y₁₂ receptor subtype and, probably to a lesser extent, the P2Y₁₃ receptor subtype. These receptors may represent therapeutic targets for treating cardiovascular pathologies, including stroke and myocardial infarctions.

Effects of two isometheptene enantiomers in isolated human blood vessels and rat middle meningeal artery - potential antimigraine efficacy

Background

Racemic isometheptene [(RS)-isometheptene] is an antimigraine drug that due to its cardiovascular side-effects was separated into its enantiomers, (R)- and (S)-isometheptene. This study set out to characterize the contribution of each enantiomer to its vasoactive profile. Moreover, rat neurogenic dural vasodilatation was used to explore their antimigraine mechanism of action.

Methods

Human blood vessel segments (middle meningeal artery, proximal and distal coronary arteries, and saphenous vein) were mounted in organ baths and concentration response curves to isometheptene were constructed. Calcitonin gene-related peptide (CGRP)-induced neurogenic dural vasodilation was elicited in the presence of the enantiomers using a rat closed cranial window model.

Results

The isometheptene enantiomers did not induce any significant contraction in human blood vessels, except in the middle meningeal artery, when they were administered at the highest concentration (100 μM). Interestingly in rats, (S)-isometheptene induced more pronounced vasopressor responses than (R)-isometheptene. However, none of these compounds affected the CGRP-induced vasodilator responses.

Conclusion

The isometheptene enantiomers displayed a relatively safe peripheral vascular profile, as they failed to constrict the human coronary artery. These compounds do not appear to modulate neurogenic dural CGRP release, therefore, their antimigraine site of action remains to be determined.

The role of α1- and α2-adrenoceptor subtypes in the vasopressor responses induced by dihydroergotamine in ritanserin-pretreated pithed rats

Background

Dihydroergotamine (DHE) is an acute antimigraine agent that displays affinity for dopamine D₂-like receptors, serotonin 5-HT_1/2 receptors and α₁/α₂-adrenoceptors. Since activation of vascular α₁/α₂-adrenoceptors results in systemic vasopressor responses, the purpose of this study was to investigate the specific role of α₁- and α₂-adrenoceptors mediating DHE-induced vasopressor responses using several antagonists for these receptors.

Methods

For this purpose, 135 male Wistar rats were pithed and divided into 35 control and 100 pretreated i.v. with ritanserin (100 μg/kg; to exclude the 5-HT₂ receptor-mediated systemic vasoconstriction). Then, the vasopressor responses to i.v. DHE (1–3100 μg/kg, given cumulatively) were determined after i.v. administration of some α₁/α₂-adrenoceptor antagonists.

Results

In control animals (without ritanserin pretreatment), the vasopressor responses to DHE were: (i) unaffected after prazosin (α₁; 30 μg/kg); (ii) slightly, but significantly, blocked after rauwolscine (α₂; 300 μg/kg); and (iii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg). In contrast, after pretreatment with ritanserin, the vasopressor responses to DHE were: (i) attenuated after prazosin (α₁; 10 and 30 μg/kg) or rauwolscine (α₂; 100 and 300 μg/kg); (ii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg); (iii) attenuated after 5-methylurapidil (α_1A; 30–100 μg/kg), L-765,314 (α_1B; 100 μg/kg), BMY 7378 (α_1D; 30–100 μg/kg), BRL44408 (α_2A; 100–300 μg/kg), imiloxan (α_2B; 1000–3000 μg/kg) or JP-1302 (α_2C; 1000 μg/kg); and (iv) unaffected after the corresponding vehicles (1 ml/kg).

Conclusion

These results suggest that the DHE-induced vasopressor responses in ritanserin-pretreated pithed rats are mediated by α₁- (probably α_1A, α_1B and α_1D) and α₂- (probably α_2A, α_2B and α_2C) adrenoceptors. These findings could shed light on the pharmacological profile of the vascular side effects (i.e. systemic vasoconstriction) produced by DHE and may lead to the development of more selective antimigraine drugs devoid vascular side effects.