Effects of a high-fat, high-carbohydrate diet on blood cells of rats

Aim. To study the effects of a high-fat, high-carbohydrate diet on erythrocytes and platelets of rats.Materials and methods. Male Wistar rats (n = 23) were used for the study. The rats were divided into a control group and an experimental group. The rats from the control group were fed with standard rat chow. The rats from the experimental group had received a high-fat and high-carbohydrate diet for 12 weeks. In the rats, body weight and blood pressure (BP) were measured, an oral glucose tolerance test was carried out, and hematological and lipid metabolism parameters were analyzed. The conductance of erythrocyte KCa-channels was measured by the potentiometric method, and platelet aggregation was determined by the turbidimetric method.Results. Feeding the rats with a high-fat, high-carbohydrate diet for 12 weeks resulted in obesity, BP elevation, hyperglycemia, impaired glucose tolerance, and dyslipidemia with pronounced triglyceridemia. In the experimental group, a rise in the number of leukocytes, mainly due to granulocytes, and an increase in the number of platelets and their collagen-induced aggregation were observed. The red blood cell count in the rats of the experimental group did not significantly differ from that of the control group. In the experimental group, multidirectional changes in the membrane potential were observed in response to the stimulation of the KCa-channels in the erythrocyte membrane with the Ca2+ ionophore A23187 or artificial redox systems.Conclusion. The obtained data indicate that a high-fat, high-carbohydrate diet leads to metabolic and hemorheological disorders that are typical of metabolic syndrome.

Electrophysiological engineering of heart-derived cells with calcium-dependent potassium channels improves cell therapy efficacy for cardioprotection

We have shown that calcium-activated potassium (KCa)-channels regulate fundamental progenitor-cell functions, including proliferation, but their contribution to cell-therapy effectiveness is unknown. Here, we test the participation of KCa-channels in human heart explant-derived cell (EDC) physiology and therapeutic potential. TRAM34-sensitive KCa3.1-channels, encoded by the KCNN4 gene, are exclusively expressed in therapeutically bioactive EDC subfractions and maintain a strongly polarized resting potential; whereas therapeutically inert EDCs lack KCa3.1 channels and exhibit depolarized resting potentials. Somatic gene transfer of KCNN4 results in membrane hyperpolarization and increases intracellular [Ca2+], which boosts cell-proliferation and the production of pro-healing cytokines/nanoparticles. Intramyocardial injection of EDCs after KCNN4-gene overexpression markedly increases the salutary effects of EDCs on cardiac function, viable myocardium and peri-infarct neovascularization in a well-established murine model of ischemic cardiomyopathy. Thus, electrophysiological engineering provides a potentially valuable strategy to improve the therapeutic value of progenitor cells for cardioprotection and possibly other indications.

Relaxation of Goat Detrusor Muscle by L-arginine Involves NO-dependent but Guanylyl Cyclase Independent Activation of KCa Channels

Background: Urinary incontinence is a major problem both in man and animals particularly dogs. L-arginine, the precursor of NO, relaxes coronary artery smooth muscle by opening of KATP channels. L-arginine has beneficial circulatory effects in patients with essential and secondary hypertension. However, not much is known about the role of L-arginine on bladder physiology. In view of this, the present work investigated the functional role of L- arginine on detrusor smooth muscle of goat. Methods: Detrusor strips of goat, collected from local abattoir were mounted in a thermostatically controlled (37° ± 0.5°C) organ bath (20 ml capacity) containing physiological solution. After 1 hr of equilibrium, carbachol (CCh) (10-5 M) was used to induce sub-maximal contraction. L-arginine (10-3 M) was added at the plateau of contraction to see any observable effect in absence and presence of modulators of NO and ion channels. Result: L- arginine (10-3 M) reversed the contractions induced by CCh (10-5 M) on detrusor tissues. Methylene blue (MB) (10-5 M), the non-specific guanylyl cyclase inhibitor, failed to attenuate the relaxant response of L-arginine but, the NO synthase inhibitor L-NAME (3 x 10-6 M) inhibited the relaxant response of L-arginine. The KATP channel blocker glibenclamide (10-6 M) failed to inhibit the relaxation induced by L-arginine while KCa channel blocker tetraethylammonium (TEA) (10-3 M) inhibited the relaxant response of L-arginine. The results of the present study suggest that L-arginine produces relaxation of goat detrusor muscle and the L-arginine-elicited relaxation is NO-dependent but guanylyl cyclase independent which activates KCa channels.

L-Arginine/Nitric Oxide Pathway and KCa Channels in Endothelial Cells: A Mini-Review

The endothelium is an organ with a key role in the maintenance of cardiovascular health through the regulation of vascular tone, vascular resistance, blood flow, and arterial pressure. These functions are related with the synthesis and release of vasoactive molecules, mainly vasodilators like nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). Both factors are released and diffused from endothelial cells to the smooth muscle cells, where there is a subsequent activation of signaling pathways that finally decrease the intracellular calcium to induce the vascular relaxation. The study of the molecular mechanisms that underlie the endothelial function still is in development, but from the evidence obtained from the endothelial cells in vitro studies are possible to partially describe the pathways to regulate the physiological endothelial function and the disturbances in pathological conditions. In this mini-review, we describe the main mechanisms for NO synthesis and the role of potassium channels related with EDHF. We include schemes and graphical summaries for better understanding of the molecular regulation of vascular tone in the human cardiovascular system.

Pharmacological Targeting of KCa Channels to Improve Endothelial Function in the Spontaneously Hypertensive Rat

Systemic hypertension is a major risk factor for the development of cardiovascular disease and is often associated with endothelial dysfunction. KCa2.3 and KCa3.1 channels are expressed in the vascular endothelium and contribute to stimulus-evoked vasodilation. We hypothesized that acute treatment with SKA-31, a selective activator of KCa2.x and KCa3.1 channels, would improve endothelium-dependent vasodilation and transiently lower mean arterial pressure (MAP) in male, spontaneously hypertensive rats (SHRs). Isolated vascular preparations exhibited impaired vasodilation in response to bradykinin (i.e., endothelial dysfunction) compared with Wistar controls, which was associated with decreased bradykinin receptor expression in mesenteric arteries. In contrast, similar levels of endothelial KCa channel expression were observed, and SKA-31 evoked vasodilation was comparable in vascular preparations from both strains. Addition of a low concentration of SKA-31 (i.e., 0.2–0.3 μM) failed to augment bradykinin-induced vasodilation in arteries from SHRs. However, responses to acetylcholine were enhanced. Surprisingly, acute bolus administration of SKA-31 in vivo (30 mg/kg, i.p. injection) modestly elevated MAP compared with vehicle injection. In summary, pharmacological targeting of endothelial KCa channels in SHRs did not readily reverse endothelial dysfunction in situ, or lower MAP in vivo. SHRs thus appear to be less responsive to endothelial KCa channel activators, which may be related to their vascular pathology.

Expression Profiling of Calcium Channels and Calcium-Activated Potassium Channels in Colorectal Cancer

Background: Colorectal cancer (CRC) is a highly devastating cancer. Ca2+-dependent channels are now considered key regulators of tumor progression. In this study, we aimed to investigate the association of non-voltage gated Ca2+ channels and Ca2+-dependent potassium channels (KCa) with CRC using the transcriptional profile of their genes. Methods: We selected a total of 35 genes covering KCa channels KCNN1–4, KCNMA1 and their subunits KCNMB1–4, endoplasmic reticulum (ER) calcium sensors STIM1 and STIM2, Ca2+ channels ORAI1–3 and the family of cation channels TRP (TRPC1–7, TRPA1, TRPV1/2,4–6 and TRPM1–8). We analyzed their expression in two public CRC datasets from The Cancer Genome Atlas (TCGA) and GSE39582. Results: KCNN4 and TRPM2 were induced while KCNMA1 and TRPM6 were downregulated in tumor tissues comparing to normal tissues. In proximal tumors, STIM2 and KCNN2 were upregulated while ORAI2 and TRPM6 were downregulated. ORAI1 decreased in lymph node metastatic tumors. TRPC1 and ORAI3 predicted poor prognosis in CRC patients. Moreover, we found that ORAI3/ORAI1 ratio is increased in CRC progression and predicted poor prognosis. Conclusions: KCa and Ca2+ channels could be important contributors to CRC initiation and progression. Our results provide new insights on KCa and Ca2+ channels remodeling in CRC.

D. russelii Venom Mediates Vasodilatation of Resistance Like Arteries via Activation of Kv and KCa Channels

Russell’s viper (Daboia russelii) venom causes a range of clinical effects in humans. Hypotension is an uncommon but severe complication of Russell’s viper envenoming. The mechanism(s) responsible for this effect are unclear. In this study, we examined the cardiovascular effects of Sri Lankan D. russelii venom in anaesthetised rats and in isolated mesenteric arteries. D. russelii venom (100 μg/kg, i.v.) caused a 45 ± 8% decrease in blood pressure within 10 min of administration in anaesthetised (100 μg/kg ketamine/xylazine 10:1 ratio, i.p.) rats. Venom (1 ng/mL–1 μg/mL) caused concentration-dependent relaxation (EC50 = 145.4 ± 63.6 ng/mL, Rmax = 92 ± 2%) in U46619 pre-contracted rat small mesenteric arteries mounted in a myograph. Vasorelaxant potency of venom was unchanged in the presence of the nitric oxide synthase inhibitor, L-NAME (100 µM), or removal of the endothelium. In the presence of high K+ (30 mM), the vasorelaxant response to venom was abolished. Similarly, blocking voltage-dependent (Kv: 4-aminopryidine; 1000 µM) and Ca2+-activated (KCa: tetraethylammonium (TEA; 1000 µM); SKCa: apamin (0.1 µM); IKCa: TRAM-34 (1 µM); BKCa; iberiotoxin (0.1 µM)) K+ channels markedly attenuated venom-induced relaxation. Responses were unchanged in the presence of the ATP-sensitive K+ channel blocker glibenclamide (10 µM), or H1 receptor antagonist, mepyramine (0.1 µM). Venom-induced vasorelaxtion was also markedly decreased in the presence of the transient receptor potential cation channel subfamily V member 4 (TRPV4) antagonist, RN-1734 (10 µM). In conclusion, D. russelii-venom-induced hypotension in rodents may be due to activation of Kv and KCa channels, leading to vasorelaxation predominantly via an endothelium-independent mechanism. Further investigation is required to identify the toxin(s) responsible for this effect.

Functional Interaction among KCa and TRP Channels for Cardiovascular Physiology: Modern Perspectives on Aging and Chronic Disease

Effective delivery of oxygen and essential nutrients to vital organs and tissues throughout the body requires adequate blood flow supplied through resistance vessels. The intimate relationship between intracellular calcium ([Ca2+]i) and regulation of membrane potential (Vm) is indispensable for maintaining blood flow regulation. In particular, Ca2+-activated K+ (KCa) channels were ascertained as transducers of elevated [Ca2+]i signals into hyperpolarization of Vm as a pathway for decreasing vascular resistance, thereby enhancing blood flow. Recent evidence also supports the reverse role for KCa channels, in which they facilitate Ca2+ influx into the cell interior through open non-selective cation (e.g., transient receptor potential; TRP) channels in accord with robust electrical (hyperpolarization) and concentration (~20,000-fold) transmembrane gradients for Ca2+. Such an arrangement supports a feed-forward activation of Vm hyperpolarization while potentially boosting production of nitric oxide. Furthermore, in vascular types expressing TRP channels but deficient in functional KCa channels (e.g., collecting lymphatic endothelium), there are profound alterations such as downstream depolarizing ionic fluxes and the absence of dynamic hyperpolarizing events. Altogether, this review is a refined set of evidence-based perspectives focused on the role of the endothelial KCa and TRP channels throughout multiple experimental animal models and vascular types. We discuss the diverse interactions among KCa and TRP channels to integrate Ca2+, oxidative, and electrical signaling in the context of cardiovascular physiology and pathology. Building from a foundation of cellular biophysical data throughout a wide and diverse compilation of significant discoveries, a translational narrative is provided for readers toward the treatment and prevention of chronic, age-related cardiovascular disease.