Lidocaine relaxation in isolated rat aortic rings is enhanced by endothelial removal: possible role of Kv, KATP channels and A2a receptor crosstalk

Novel Strategies to Improve the Cardioprotective Effects of Cardioplegia

The use of cardioprotective strategies as adjuvants of cardioplegic solutions has become an ideal alternative for the improvement of post-surgery heart recovery. The choice of the optimal cardioplegia, as well as its distribution mechanism, remains controversial in the field of cardiovascular surgery. There is still a need to search for new and better cardioprotective methods during cardioplegic procedures. New techniques for the management of cardiovascular complications during cardioplegia have evolved with new alternatives and additives, and each new strategy provides a tool to neutralize the damage after ischemia/reperfusion events. Researchers and clinicians have committed themselves to studying the effect of new strategies and adjuvant components with the potential to improve the cardioprotective effect of cardioplegic solutions in preventing myocardial ischemia/reperfusion-induced injury during cardiac surgery. The aim of this review is to explore the different types of cardioplegia, their protection mechanisms, and which strategies have been proposed to enhance the function of these solutions in hearts exposed to cardiovascular pathologies that require surgical alternatives for their corrective progression.

[Risks of progression of cerebrovascular pathology associated with the activity of the brain purinergic system]

Until now, there is no understanding of the relationship between risk factors and the progression of cerebrovascular pathology. The review presents facts that confirm the involvement of various subtypes of purine P2 receptors in neuron activation, growth and myelination of axons, migration and microglia phagocytosis, astrogliosis, regulation of vascular tone, thrombosis and angiogenesis, neuroinflammation and immune responses. The data suggest the possibility of the activation of purinergic system of the brain during the development of main risk factors for cerebrovascular pathology (age, arterial hypertension, diabetes), as a stereotypical mechanism that can affect the homeostasis of the ensemble "neuron-glia-capillary". Purinergic P2 receptors may be a potential target for the development of pharmacological methods to limit the progression of cerebrovascular pathology.

Lidocaine improves cerebral ischemia-reperfusion injury in rats through cAMP/PKA signaling pathway

Influence of lidocaine on rats with cerebral ischemia-reperfusion injury (CIRI) was studied to explore its mechanism of action. A total of 30 Sprague-Dawley rats were randomly divided into control group and model group, and the rat model of CIRI was prepared by the suture-occluded method in the model group. Then the rats in the model group were randomly assigned into the model group (n=10) and the lidocaine group (n=10). The neurological function score of rats was evaluated, and the levels of serum B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) in rats were determined using ELISA. TUNEL assay was performed to detect the neuronal apoptosis in the brain of rats. The messenger ribonucleic acid (mRNA) and protein expression levels of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) were measured via RT-PCR and western blotting, respectively. Compared with those in the control group, the rats in the model group had an elevated neurological function score, a raised level of Bcl-2, but a reduced level of Bax in the serum, an obviously increased rate of neuronal apoptosis in the brain and decreased mRNA and protein levels of cAMP and PKA in cerebral tissues. The rats in lidocaine group had a lower neurological function score, a lower level of Bcl-2, but a higher level of Bax in the serum, an evidently lower rate of neuronal apoptosis in the brain and higher mRNA and protein levels of cAMP and PKA in cerebral tissues than those in the model group. Lidocaine can improve the neurological function of rats with CIRI and inhibit neuronal apoptosis in the brain, and its mechanism of action may be related to the activation of the cAMP/PKA signaling pathway.

Adenosine and lidocaine (AL) combination dilates intimally damaged rat thoracic aortic rings and guinea pig mesenteric arteries: possible significance to cardiac surgery

New pharmacotherapies are required to improve vessel graft protection and prevent vasoconstriction and spasm in CABG surgery. Previously we have studied adenosine (A) and lidocaine (L) relaxation in rat aortic rings, and reported a possible crosstalk between L relaxation and adenosine A_2a receptor inhibition. The aim of the present study was to examine the effect of AL combination compared to A and L alone on relaxation in intact and denuded rat aortic rings and in guinea-pig pressurized mesenteric arterial segments. Aortic rings were harvested from Sprague-Dawley rats and equilibrated in an organ bath containing modified Krebs-Henseleit (KH) solution, pH 7.4, 37°C. Rings were pre-contracted sub-maximally with 0.3 µM norepinephrine, and the effects of increasing AL, A or L (up to 1.0 mM) were examined in intact and denuded rings. Mesenteric artery segments were isolated from guinea-pigs and mounted in an arteriograph containing KH solution and pressurised to 60 mmHg. Arteries were preconstricted with 10^-8 M vasopressin and AL, A, or L was administered luminally or abluminally. Diameters were measured using video-microscopy. We report in intact rat aortic rings, AL increased relaxation from 21 to 100% (0.1-1.0 mM) and relaxation was endothelium-independent. Adenosine alone was also a potent relaxant of aortic rings but, unlike AL relaxation, it was partially endothelium-dependent. In intact mesenteric artery segments, increasing luminal AL produced a potent endothelium-independent dilation (up to 90%). Adenosine dilation was endothelium-independent but not lidocaine, which produced 33% dilation only after endothelial removal. Extra-luminal AL and A led to 76% and 80% dilationin intact segments respectively, whereas L resulted in constriction (10-17%). In conclusion, we show that AL can dilate aortic rings and mesenteric artery segments by up to 90% regardless of whether the endothelium is intact. We discuss the potential translational significance of AL to improve conduit protection in cardiac surgery, and other major surgeries.