KATP channels are regulators of programmed cell death and targets for the creation of novel drugs against ischemia/reperfusion cardiac injury

BACKGROUND

The use of percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) is associated with a mortality rate of 5%-7%. It is clear that there is an urgent need to develop new drugs that can effectively prevent cardiac reperfusion injury. ATP-sensitive K+ (KATP ) channel openers (KCOs) can be classified as such drugs.

RESULTS

KCOs prevent irreversible ischemia and reperfusion injury of the heart. KATP channel opening promotes inhibition of apoptosis, necroptosis, pyroptosis, and stimulation of autophagy. KCOs prevent the development of cardiac adverse remodeling and improve cardiac contractility in reperfusion. KCOs exhibit antiarrhythmic properties and prevent the appearance of the no-reflow phenomenon in animals with coronary artery occlusion and reperfusion. Diabetes mellitus and a cholesterol-enriched diet abolish the cardioprotective effect of KCOs. Nicorandil, a KCO, attenuates major adverse cardiovascular event and the no-reflow phenomenon, reduces infarct size, and decreases the incidence of ventricular arrhythmias in patients with acute myocardial infarction.

CONCLUSION

The cardioprotective effect of KCOs is mediated by the opening of mitochondrial KATP (mitoKATP ) and sarcolemmal KATP (sarcKATP ) channels, triggered free radicals' production, and kinase activation.

The Role of P2Y6 Receptors in the Mechanisms of the Neuroprotective Effect of Citicoline

Spontaneous bioelectrical activity of the brain and the duration of gasping were recorded in mice during modeling of global strangulation ischemia of the brain against the background of preventive administration of citicoline. The maximum neuroprotective effect of citicoline was observed when it was administered 60 min before the simulation of ischemia and was completely prevented by preliminary administration of a selective P₂Y₆ receptor antagonist MRS2578. The obtained experimental data attest to the leading role of receptor mechanisms in the implementation of neuroprotective activity of citicoline.

Apelin Is a Prototype of Novel Drugs for the Treatment of Acute Myocardial Infarction and Adverse Myocardial Remodeling

In-hospital mortality in patients with ST-segment elevation myocardial infarction (STEMI) is 5-6%. Consequently, it is necessary to develop fundamentally novel drugs capable of reducing mortality in patients with acute myocardial infarction. Apelins could be the prototype for such drugs. Chronic administration of apelins mitigates adverse myocardial remodeling in animals with myocardial infarction or pressure overload. The cardioprotective effect of apelins is accompanied by blockage of the MPT pore, GSK-3β, and the activation of PI3-kinase, Akt, ERK1/2, NO-synthase, superoxide dismutase, glutathione peroxidase, matrix metalloproteinase, the epidermal growth factor receptor, Src kinase, the mitoK_ATP channel, guanylyl cyclase, phospholipase C, protein kinase C, the Na⁺/H⁺ exchanger, and the Na⁺/Ca²⁺ exchanger. The cardioprotective effect of apelins is associated with the inhibition of apoptosis and ferroptosis. Apelins stimulate the autophagy of cardiomyocytes. Synthetic apelin analogues are prospective compounds for the development of novel cardioprotective drugs.

Regulation of autophagy of the heart in ischemia and reperfusion

Ischemia/reperfusion (I/R) of the heart leads to increased autophagic flux. Preconditioning stimulates autophagic flux by AMPK and PI3-kinase activation and mTOR inhibition. The cardioprotective effect of postconditioning is associated with activation of autophagy and increased activity of NO-synthase and AMPK. Oxidative stress stimulates autophagy in the heart during I/R. Superoxide radicals generated by NADPH-oxidase acts as a trigger for autophagy, possibly due to AMPK activation. There is reason to believe that AMPK, GSK-3β, PINK1, JNK, hexokinase II, MEK, PKCα, and ERK kinases stimulate autophagy, while mTOR, PKCδ, Akt, and PI3-kinase can inhibit autophagy in the heart during I/R. However, there is evidence that PI3-kinase could stimulate autophagy in ischemic preconditioning of the heart. It was found that transcription factors FoxO1, FoxO3, NF-κB, HIF-1α, TFEB, and Nrf-2 enhance autophagy in the heart in I/R. Transcriptional factors STAT1, STAT3, and p53 inhibit autophagy in I/R. MicroRNAs could stimulate and inhibit autophagy in the heart in I/R. Long noncoding RNAs regulate the viability and autophagy of cardiomyocytes in hypoxia/reoxygenation (H/R). Nitric oxide (NO) donors and endogenous NO could activate autophagy of cardiomyocytes. Activation of heme oxygenase-1 promotes cardiomyocyte tolerance to H/R and enhances autophagy. Hydrogen sulfide increases cardiac tolerance to I/R and inhibits apoptosis and autophagy via mTOR and PI3-kinase activation.

Pharmacological Approaches to Limit Ischemic and Reperfusion Injuries of the Heart. Analysis of Experimental and Clinical Data on P2Y12 Receptor Antagonists

High mortality among people with acute myocardial infarction is one of the most urgent problems of modern cardiology. And in recent years, much attention has been paid to the search for pharmacological approaches to prevent heart damage. In this review, we tried to analyze data on the effect of P2Y₁₂ receptor antagonists on the ischemia/reperfusion tolerance of the heart.

Ischemic and reperfusion injuries of the heart underlie the pathogenesis of acute myocardial infarction (AMI) and sudden cardiac death. The mortality rate is still high and is 5–7% in patients with ST-segment elevation myocardial infarction. The review is devoted to pharmacological approaches to limitation of ischemic and reperfusion injuries of the heart. The article analyzes experimental evidence and the clinical data on the effects of P2Y₁₂ receptor antagonists on the heart’s tolerance to ischemia/reperfusion in animals with coronary artery occlusion and reperfusion and also in patients with AMI. Chronic administration of ticagrelor prevented adverse remodeling of the heart. There is evidence that sphingosine-1-phosphate is the molecule that mediates the infarct-reducing effect of P2Y₁₂ receptor antagonists. It was discussed a role of adenosine in the cardioprotective effect of ticagrelor.

[Anticonvulsant and neuroprotective effects of cyclopentyladenosine on the model of convulsive status in rats]

The neuroprotective and anticonvulsant effects of cyclopentyladenosine (CPA) have been studied on a new experimental model of the convulsive status in rats aged 3-4 months and 10 days. The convulsive status was modeled by intracerebroventricular injection of ferakril (water-soluble polymer of polyacrylic acid) solution. It is established that prophylactic administration of CPA results in a relatively lower degree of neurological deficit, both in the acute phase and on the next day, compared to the untreated control. Considering that adenosine receptor agonists are analogs of the natural metabolites that have minimal side effects and expressed neuroprotective properties, the use of agents of this group is perspective for both prevention and treatment of seizure conditions in neurology and neurosurgery.

Endoscopic third ventriculostomy in patients younger than 2 years: outcome analysis of 41 hydrocephalus cases

OBJECT

The object of this study was to analyze the outcome of endoscopic third ventriculostomy (ETV) in patients under 2 years of age and investigate factors related to ETV success or failure in this patient population.

METHODS

The authors reviewed their experience in using endoscopic third ventriculostomy (ETV) in the treatment of 41 hydrocephalus patients younger than 2 years. The mean duration of follow-up was 45 months. The relationship between ETV efficacy and the following variables was analyzed: cause of hydrocephalus, level of CSF occlusion, primary versus secondary ETV, type of surgical procedure, head circumference, patient age at ETV, patient age at first manifestation of hydrocephalus, and anatomical features of the ventricle. Success of ETV was assessed based on the results of neurological examination and postoperative imaging during the follow-up period.

RESULTS

The authors performed 32 primary ETVs and 10 secondary ETVs (ETV after hydrocephalus surgery) in 41 patients (a second ETV was performed in 1 patient). The success rates of primary and secondary ETV were 75.8 and 55.6%, respectively (no significant difference, p = 0.15). The ETV was clinically and radiologically successful in 30 (71.4%) of 42 procedures during a mean (+/- SD) follow-up period of 45.0 +/- 4.8 months (range 12-127 months). A negative relationship was found between success of ETV and the thickness of the floor of the third ventricle (the most effective procedures were those in which the floor of the ventricle was thinnest [p < 0.05]). There was a highly significant correlation between ETV success and prolapse of the ventricle floor (p < 0.001). Also, there was an inverse relationship between ventricle floor thickness and the width of the third ventricle (p < 0.005). In our group of patients there was significant correlation between ETV success and patient age at onset of hydrocephalus (the most effective procedures were in patients in whom signs of hydrocephalus first occurred after 1 month of age [p = 0.02]).

CONCLUSIONS

Endoscopic third ventriculostomy was successful in 71.4% of procedures in children younger than 2 years and in 75.0% of procedures in infants. Success of ETV in children younger than 2 years depends not on the age of the patient or cause of hydrocephalus but on the thickness of the floor of the third ventricle and the patient's age at first manifestation of hydrocephalus.

[Effect of cyclopentyladenosine on the orientation, exploratory, and emotional behavior of rats with model brain injury]

Effects of a local compression brain injury and the preventive application of cyclopentyladenosine (CPA) on the behavior of rats in the open field test was investigated. It is established that the local injury of a parietal cortex causes intensification of the orientation--research behavior and an increase in the emotional stress in rats. A protective action of CPA was manifested by a decrease in the expressiveness and duration of disturbances in the emotional and orientation--research behavior of animals in the open field test.

[Efficiency of neuroendoscopic operations in achieving shunt independency in hydrocephalus with liquor-shunting system dysfunction]

OBJECTIVE

to evaluate the efficiency of endoscopic treatments in achieving shunt independency in patients with hydrocephalus and shunt dysfunction.

SUBJECTS AND METHODS

endoscopic treatment was performed in 28 patients (15 males and 13 females) aged 7.0 +/- 1.2 years (0.5-24 years) with hydrocephalus and CSF shunt dysfunction. The interval between the first shunt implantation and endoscopic surgery (the time of shunt dependency) was 43.4 +/- 7.8 months (5-180 months). All operations were made using the universal Gaab neuroendoscopic system (Karl Storz GmbH and Co., Germany). The follow-up lasted 49.4 +/- 6.9 months (6-120 months).

RESULTS

All the patients were successfully operated on, without intraoperative complications and deaths being observed. Surgical interventions were as follows: endoscopic ventriculocisternostomy (n=23), endoscopic aqueductoplasty (n=1), and endoscopic cystoventriculocistemrnostomy (n=4). In 24 of the 28 patients, the symptoms of intracranial hypertension regressed completely. CSF shunt reimplantation was required in 3 cases and prolonged external drainage in 1 case of existing ventriculitis. It should be noted that 24 of the 28 patients became shunt-independent; a shunt was removed in 13.

[The topographic anatomy of the interpeduncular cistern and endoscopic ventriculocisternostomy in the region of the bottom of the third ventricle]

The interpeduncular cistern was microanatomically studied on 14 anatomic specimens of the brain. It was divided into 2 parts: superficial (free) and deep (vascular). The upper interpeduncular cistern wall was divided into hypothalamic and mesencephalic parts. The interpeduncular cistern is connected with the ambient, pretontine, carotid, cerebellopontine, oculomotor, and peduncular cisterns. It is a composite space-occupying, structural formation. Liliequist's membrane is the basic membranous component of a cistern. The proposed division makes it possible to study different parts of the interpeduncular cistern qualitatively and quantitatively and to define clear topographic and anatomic criteria as a guideline in this field.

Changes in the steady-state potential in rats with focal cerebral ischemia receiving cyclopentyladenosine

Brain function and neuroprotective activity of cyclopentyladenosine in rats with focal cerebral ischemia were evaluated by recording the steady-state potential. Cerebral ischemia was modeled by intravasal occlusion of the left internal carotid and middle cerebral arteries and bilateral occlusion of the common carotid arteries. Recording of the steady-state brain potential during experimental ischemia allowed identifying the development of ischemic depolarization by a negative potential shift. Changes in the steady-state potential after cyclopentyladenosine administration reflected delayed development of ischemic depolarization in the nervous tissue. Cyclopentyladenosine holds much promise for the protection of nerve cells from ischemic injury.

[Protective effect of A-agonists in a minimum invasive model of spinal cord ischemia in rats]

The neuroprotective properties of N6-cyclohexyladenosine (CHA) and N6-cyclopentyladenosine (CPA), adenosine receptor agonists (A-agonists), were studied on a model of spinal cord ischemia (SCI) in rats (most closely reproducing the analogous clinical pathological process in humans). The SCI model was induced by intravasal occlusion of the abdominal aorta and its branches. CHA and CPA were introduced by intracerebroventricular injections in a dose of 25 micrograms/kg, 60 min before SCI induction. The protective effect was judged by comparing the patterns of neurological and histopathological disturbances in the untreated control (ischemia) and on the CHA or CPA background. The A-agonist CPA produced a pronounced, statistically reliable neuroprotector effect on the minimum invasive SCI model studied. CHA is also a statistically reliable but less effective neuroprotector. The A-agonists may have good prospects in clinics.

[Protective effect of adenosine receptor agonists in a model of spinal cord injury in rats]

Possibilities of the neuroprotector therapy using adenosine and cyclopentyladenosine (CPA), an adenosine receptor agonist, were studied on a model of spinal cord injury by compression in rats (most closely reproducing the analogous clinical pathological process in humans). The model was induced by slow, graded compression of the spinal cord at the thoracic level. Adenosine and CPA were introduced 60 min before injury by subcutaneous injections in a dose of 300 and 2.5 micrograms/kg, respectively. The protective effect was judged by comparing the neurological, electromyographic, and histopathological changes in animals with the model injury and in the control group (adenosine and CPA background). The A1-agonist CPA injections produced a pronounced, statistically significant neuroprotector effect on the given spinal cord injury model in rats. The neuroprotective effect of adenosine was significant but not as strong. It is concluded that it is expedient to use A-agonists in clinics.

[Protective effect of cyclopentyladenosine in a minimally invasive model of acute cerebral focal ischemia in rats]

The neuroprotector properties of cyclopentyladenosine (CPA), an adenosine receptor agonist, were studied on a model of focal brain ischemia in rats (reproducing a clinical pathological process in humans). The model of the focal brain ischemia in rats was induced by intravasal occlusion of left carotid artery, middle cerebral artery, and by bilateral occlusion of both carotid arteries. CPA was introduced by intracerebroventricular injections in a dose of 25 micrograms/kg, 60 min before ischemia induction. The protective effect was judged by comparing the neurological and histopathological disturbances in the control (untreated ischemia) and on the CPA background. CPA injections produced a pronounced neuroprotector effect on the minimum-invasive focal brain ischemia model in rats.

New minimally invasive model of spinal cord ischemia in rats

We developed a new minimally invasive model of spinal cord ischemia in rats: intravascular occlusion of the abdominal aorta and its branches. This model can be used on small laboratory animals and allows qualitatively and quantitatively evaluating the morphofunctional state of the nervous system during spinal cord ischemia by clinical manifestations and histological changes. Selective intravascular occlusion determines minimal invasiveness and adequacy of the proposed model to in vivo pathological processes. This model of spinal cord ischemia can be used in experimental pharmacology for evaluation of neuroprotective activity of various drugs and bioactive substances.

[Minimum-invasive model of the rat brain focal ischemia]

The problem of brain ischemia damage treatment stimulates the search for new effective methods, which are studied on various experimental models. Most of such models possess significant disadvantages, producing hypoxia in the whole organism, being poorly controlled, involving serious traumas, and still being far from true pathological mechanisms accompanying the ischemia development. A model of focal brain ischemia in rats, induced by middle cerebral artery intravasal occlusion, is free of these disadvantages.

[The biological range and characteristics of the importance of adenosine receptors for the resistance of the brain to total ischemia]

In the total brain ischemia the cerebroprotective effect (CPE) of adenosine was pronounced in the following order: mouse > rat approximately guinea pig (males > females). The sensitizing effect (SE) of theophylline is the same in different species but is more pronounced in females compared to males. Newborn rats are much more tolerant to the total brain ischemia. The adenosine CPE increases and the theophylline SE decreases with age. The adenosine receptor component, evidently, contributes greatly to the natural tolerance of newborn animals to the total brain ischemia.

[The effect of adenosine receptor agonists on the normal cerebral blood flow and in subsequent ischemia]

Nonconformity of arterial pressure (AP) and cerebral blood flow (CBF) to the normal distribution necessitates the use of nonparametric criteria. Cerebroprotective doses of adenosine and cyclohexyladenosine significantly decrease AP and reduce (or virtually do not change) CBF. In conditions of following occlusion of carotid arteries AP is lower and CBF is somewhat better or the same as in the control (ischemia). Changes in CBF can be only an additional contribution to the high cerebroprotective effect of the A-receptor agonists.

[The comparative characteristics and receptor mechanism of the effect of adenosine-receptor agonists in total cerebral ischemia]

The duration of gasping has no normal distribution, so nonparametric statistic criteria should be used. Three adenosine receptor agonists have a highly cerebro-protective effect which decreases in the order: N-ethylcarboxamide adenosine > > cyclohexyl adenosine > adenosine. Theophylline completely blocks these effects. Thus, they act through adenosine receptors. Adenosine receptor agonist are likely to protect themselves neurons.

[Protective effect of adenosine in total brain ischemia]

Adenosine has prominent cerebro-protective effect at total brain ischemia. Other nucleotides and nucleosides are less active or have no effect at all. It suggests participation of A-receptors. Adenosine is more effective than 8 other drugs that have protective effect in different models of brain ischemia (nimodipine, gamma-hydroxybutyrate etc).