endothelin-1 and cariporide

This study aimed to explore the signaling pathways involved in the positive inotropic effect (PIE) of low doses of endothelin-1 (ET-1). Cat papillary muscles were used for force and intracellular Na(+) concentration (Na(+)(i)) measurements, and isolated cat ventricular myocytes for patch-clamp experiments. ET-1 (5 nmol/L) induced a PIE and an associated increase in Na(+)(i) that were abolished by Na(+)/H(+) exchanger (NHE) inhibition with HOE642. Reverse-mode Na(+)/Ca(2+) exchanger (NCX) blockade with KB-R7943 reversed the ET-1-induced PIE. These results suggest that the ET-1-induced PIE is totally attributable to the NHE-mediated Na(+)(i) increase. However, an additional direct stimulating effect of ET-1 on NCX after the necessary increase in Na(+)(i) could occur. Thus, the ET-1-induced increase in Na(+)(i) and contractility was compared with that induced by partial inhibition of the Na(+)/K(+) ATPase by lowering extracellular K(+) (K(+)(o)). For a given Na(+)(i), ET-1 induced a greater PIE than low K(+)(o). In the presence of HOE642 and after increasing contractility and Na(+)(i) by low K(+)(o), ET-1 induced an additional PIE that was reversed by KB-R7943 or the protein kinase C (PKC) inhibitor chelerythrine. ET-1 increased the NCX current and negatively shifted the NCX reversal potential (E(NCX)). HOE642 attenuated the increase in NCX outward current and abolished the E(NCX) shift. These results indicate that whereas the NHE-mediated ET-1-induced increase in Na(+)(i) seems to be mandatory to drive NCX in reverse and enhance contractility, Na(+)(i)-independent and PKC-dependent NCX stimulation appears to additionally contribute to the PIE. However, it is important to stress that the latter can only occur after the primary participation of the former.

Topics: Animals; Cardiotonic Agents; Cats; Electric Conductivity; Endothelin-1; Guanidines; Heart Ventricles; In Vitro Techniques; Intracellular Fluid; Myocardial Contraction; Myocytes, Cardiac; Papillary Muscles; Patch-Clamp Techniques; Protein Kinase C; Signal Transduction; Sodium; Sodium-Calcium Exchanger; Sulfones

The effects of pretreatment with cariporide (HOE 642 Aventis Pharma, Strasbourg-Cedex, France), a Na+-H+ exchanger (NHE) blocker, were studied in a cerebral ischemia-reperfusion model of hypothermic arrest.. Fifteen Yorkshire-Duroc pigs (37.1 +/- 4.2 kg) underwent femoral-jugular bypass and 90 minutes of deep hypothermic circulatory arrest at 19 degrees C. Ten animals were untreated, whereas 5 received 5 mg/kg of intravenous cariporide before cooling. After rewarming and off cardiopulmonary bypass, the pigs were weaned from anesthesia and followed for 24 hours. A standardized neurologic scoring system assessed brain functional recovery. Biochemical markers were used to analyze cellular injury. Control studies without circulatory arrest were done in 2 animals that underwent similar cooling and rewarming.. Neurologic recovery was rapid and complete in the nonischemic controls and in all pretreated animals. Conversely, at 24 hours, all untreated pigs exhibited a cloudy or stuporous level of consciousness, abnormal positioning, and with only one exception, could not sit or stand. The gradation of neurologic score (evaluating central nervous system, motor and sensory functions, respiration condition, level of consciousness, and behavior) was 0 +/- 0 (0 = normal, 500 = brain death) in the treated group, compared with 124 +/- 59 in the untreated animals. Biochemical analysis showed every variable of whole-body injury (including conjugated dienes (p < 0.05), serum aspartate amino transferase (p < 0.01), creatine kinase p < 0.001) and endothelin-1 (p < 0.001) to be higher in the untreated group.. NHE function alters experimental brain ischemia-reperfusion damage. These observations imply that NHE inhibition therapy before ischemia may improve neurologic protection in adult and infant patients undergoing cerebral ischemia during procedures that use hypothermic circulatory arrest.

Topics: Animals; Biomarkers; Creatine Kinase; Endothelin-1; Glutamyl Aminopeptidase; Guanidines; Heart Arrest; Heart Arrest, Induced; Hypothermia, Induced; Ischemic Attack, Transient; Reperfusion Injury; Sodium-Hydrogen Exchangers; Sulfones; Swine

Inhibition of the Na+/H+ exchanger before ischemia protects against ischemia-reperfusion injury, but use as pretreatment before blood cardioplegic protection or as a supplement to controlled blood cardioplegic reperfusion was not previously tested in jeopardized hearts.. Control studies tested the safety of glutamate-aspartate-enriched blood cardioplegic solution in 4 Yorkshire-Duroc pigs undergoing 30 minutes of aortic clamping without prior unprotected ischemia. Twenty-four pigs underwent 30 minutes of unprotected normothermic global ischemia to create a jeopardized heart. Six of these hearts received normal blood reperfusion, and the other 18 jeopardized hearts underwent 30 more minutes of aortic clamping with cardioplegic protection. In 12 of these, the Na+/H+ exchanger inhibitor cariporide was used as intravenous pretreatment (n = 6) or added to the cardioplegic reperfusate (n = 6).. Complete functional, biochemical, and endothelial recovery occurred after 30 minutes of blood cardioplegic arrest without preceding unprotected ischemia. Thirty minutes of normothermic ischemia and normal blood reperfusion produced 33% mortality and severe left ventricular dysfunction in survivors (preload recruitable stroke work, 23% +/- 6% of baseline levels), with raised creatine kinase MB, conjugated dienes, endothelin-1, myeloperoxidase activity, and extensive myocardial edema. Blood cardioplegia was functionally protective, despite adding 30 more minutes of ischemia; there was no mortality, and left ventricular function improved (preload recruitable stroke work, 58% +/- 21%, p < 0.05 versus normal blood reperfusion), but adverse biochemical and endothelial variables did not change. In contrast, Na+/H+ exchanger inhibition as either pretreatment or added during cardioplegic reperfusion improved myocardial recovery (preload recruitable stroke work, 88% +/- 9% and 80% +/- 7%, respectively, p < 0.05 versus without cariporide) and comparably restored injury variables.. Na+/H+ exchanger blockage as either pretreatment or during blood cardioplegic reperfusion comparably delays functional, biochemical, and endothelial injury in jeopardized hearts.

Topics: Animals; Blood; Cardioplegic Solutions; Creatine Kinase; Creatine Kinase, MB Form; Endothelin-1; Guanidines; Isoenzymes; Myocardial Reperfusion Injury; Sodium-Hydrogen Exchangers; Sulfones; Swine; Ventricular Function, Left

In certain cardiovascular disorders, such as congestive heart failure and ischemic heart disease, several endogenous regulators, including norepinephrine (NE) and endothelin-1 (ET-1), are released from various types of cell. Because plasma levels of these regulators are elevated, it seems likely that cardiac contraction might be regulated by crosstalk among these endogenous regulators. We studied the regulation of cardiac contractile function by crosstalk between ET-1 and NE and its relationship to Ca2+ signaling in canine ventricular myocardium. ET-1 alone did not affect the contractile function. However, in the presence of NE at subthreshold concentrations (0.1 to 1 nmol/L), ET-1 had a positive inotropic effect (PIE). In the presence of NE at higher concentrations (100 to 1000 nmol/L), ET-1 had a negative inotropic effect. ET-1 had a biphasic inotropic effect in the presence of NE at an intermediate concentration (10 nmol/L). The PIE of ET-1 was associated with an increase in myofilament sensitivity to Ca2+ ions and a small increase in Ca2+ transients, which required the simultaneous activation of protein kinase A (PKA) and PKC. ET-1 elicited translocation of PKCepsilon from cytosolic to membranous fraction, which was inhibited by the PKC inhibitor GF 109203X. Whereas the Na+-H+ exchange inhibitor Hoe 642 suppressed partially the PIE of ET-1, detectable alteration of pHi did not occur during application of ET-1 and NE. The negative inotropic effect of ET-1 was associated with a pronounced decrease in Ca2+ transients, which was mediated by pertussis toxin-sensitive G proteins, activation of protein kinase G, and phosphatases. When the inhibitory pathway was suppressed, ET-1 had a PIE even in the absence of NE. Our results indicate that the myocardial contractility is regulated either positively or negatively by crosstalk between ET-1 and NE through different signaling pathways whose activation depends on the concentration of NE in the dog.

Topics: Animals; Calcium Signaling; Cardiotonic Agents; Culture Techniques; Cyclic AMP-Dependent Protein Kinases; Dogs; Dose-Response Relationship, Drug; Drug Interactions; Endothelin-1; Enzyme Inhibitors; Guanidines; Heart Ventricles; Indoles; Maleimides; Myocardial Contraction; Myocytes, Cardiac; Norepinephrine; Pertussis Toxin; Protein Kinase C; Signal Transduction; Sulfones; Ventricular Function

This work was aimed to prove that release/formation of endogenous endothelin acting in an autocrine/paracrine fashion contributes to the increase in contractility promoted by a low dose of angiotensin II.. Isolated cat papillary muscles were used for force, pH(i), [Na(+)](i) and [Ca(2+)](i) measurements and isolated cat myocytes for patch-clamp experiments.. In papillary muscles, 1.0 nmol/l angiotensin II increased force by 23+/-2% (n=4, P<0.05), [Na(+)](i) by 2.2+/-0.2 mmol/l (n=4, P<0.05), and peak (but not diastolic) Ca(2+) from 0.674+/-0.11 to 0.768+/-0.13 micromol/l (n=4, P<0.05), without affecting pH(i). Force and [Na(+)](i) increase were abolished by inhibition of the Na(+)/H(+) exchanger (NHE) with the inhibitor HOE642, blockade of endothelin receptors with the nonselective antagonist TAK044 and by inhibition of the endothelin-converting enzyme with phosphoramidon. Force but not [Na(+)](i) increase was abolished by inhibition of reverse Na(+)/Ca(2+) exchange (NCX) with the inhibitor KB-R7943. Similar increase in force (21+/-2%, n=4, P<0.05) and in [Na(+)](i) (2.4+/-0.4 mmol/l, n=4, P<0.05) that were also suppressed by TAK044 and HOE642 were induced by exogenous 5.0 nmol/l endothelin-1. KB-R7943 reverted the endothelin-1 effect on force but not on [Na(+)](i). In isolated myocytes, exogenous endothelin-1 dose-dependently increased the NCX current and shifted the NCX reversal potential (E(NCX)) to a more negative value (DeltaE(NCX): -10+/-3 and -17+/-5 mV, with 1 and 10 nmol/l endothelin-1, respectively, n=12). The latter effect was prevented by HOE642.. Taken together, the results indicate that a low dose of angiotensin II induces release of endothelin, which, in autocrine/paracrine fashion activates the Na(+)/H(+) exchanger, increases [Na(+)](i) and changes E(NCX), promoting the influx of Ca(2+) that leads to a positive inotropic effect (PIE).

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Cats; Electrophysiology; Endothelin Receptor Antagonists; Endothelin-1; Enzyme Inhibitors; Glycopeptides; Guanidines; In Vitro Techniques; Losartan; Muscle Contraction; Papillary Muscles; Patch-Clamp Techniques; Peptides, Cyclic; Sodium-Calcium Exchanger; Sulfones; Thiourea

The preconditioning effects of the adjunctive, cardiac-specific sodium-hydrogen ion exchange inhibitor cariporide (cariporide mesilate, HOE 642) were studied in hearts subjected to 30 minutes of normothermic ischemia and reperfusion to assess myocardial and endothelial changes.. Sixteen Yorkshire-Duroc pigs (27-34 kg) receiving cardiopulmonary bypass underwent either cardiopulmonary bypass alone (control, n = 4) or 30 minutes of normothermic ischemia, followed by 30 minutes of blood reperfusion (n = 12). Six hearts were treated with 5 mg/kg cariporide administered intravenously 15 minutes before ischemia.. Cardiopulmonary bypass alone caused no changes. Conversely, 30 minutes of global normothermic ischemia caused 33% mortality and, in survivors, depression of left ventricular function to 22% +/- 6% of baseline preload recruitable stroke work and increased creatine kinase MB by 406% (88 +/- 13 U/L), conjugated dienes by 17% (161 +/- 0.2 AU/mL), and myeloperoxidase activity by 297% (0.036 +/- 0.005 U/g). Myocardial edema developed (3.5% water gain). Coronary sinus endothelin 1 increased by 111% (2.05 +/- 0.38 pg/mL), and nitric oxide production decreased by 10%. These adverse effects were limited by pretreatment with cariporide, which allowed complete survival and restored preload recruitable stroke work to 78% +/- 11%. Measurements of creatine kinase MB, conjugated dienes, myeloperoxidase, water, and endothelin 1 returned to baseline values, and nitric oxide production was accentuated 3-fold.. These observations show that adjunctive pretreatment with cariporide delays myocardial and endothelial injury during ischemia and reperfusion, limits oxygen-derived radical injury, restores function, reduces edema, and preserves endothelin and nitric oxide balance at normal values. The myeloperoxidase changes show that less white blood cell adherence supports reduced reperfusion endothelial damage.

Topics: Animals; Anti-Arrhythmia Agents; Cardiopulmonary Bypass; Creatine Kinase; Creatine Kinase, MB Form; Endothelin-1; Guanidines; Ischemic Preconditioning, Myocardial; Isoenzymes; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Peroxidase; Sulfones; Swine; Time Factors

Myocardial ischemia and reperfusion cause myocyte and vascular dysfunction, frequently termed "stunning." We hypothesized that inhibiting the Na(+)/H(+) exchanger subtype 1 isoform (NHE(1)) during ischemia and reperfusion limits myocardial and coronary microvascular stunning. Anesthetized rats completed 2 x 10-min coronary artery occlusions separated by 5-min of reperfusion, followed by 15 or 60 min of reperfusion. Vehicle (saline) or the NHE(1) inhibitor cariporide (HOE-642) was administered 15 min before ischemia and was continued throughout each protocol. After reperfusion, hearts were excised, and the reactivity of resistance arteries (internal diameter, approximately 120 microm) was assessed. The first derivative of left ventricular (LV) pressure, LV developed pressure, and LV systolic wall thickening were depressed (P < 0.05) similarly in vehicle- and cariporide-treated rats during ischemia and after 15 or 60 min of reperfusion compared with sham-operated animals that were not exposed to ischemia (i.e., controls). In vessels obtained after 15 min of reperfusion, the maximal response to acetylcholine-induced relaxation (10(-8)-10(-4) M) was blunted (P < 0.05) in vessels from vehicle- (approximately 35%) and cariporide-treated rats (approximately 55%) compared with controls (approximately 85%). However, the percent relaxation to acetylcholine was greater (P < 0.05) in cariporide-treated rats compared with vehicle-treated rats. Maximal contractile responses to endothelin-1 (10(-11)-10(-7) M) were increased (P < 0.05) similarly in vehicle- and cariporide-treated rats compared with controls. Relaxation to sodium nitroprusside (10(-4) M) was not different among groups. Results were similar in vessels obtained from animals after 60 min of reperfusion. These findings suggest that NHE(1) inhibition before coronary occlusion lessens ischemia-induced microvascular dysfunction for 15-60 min after reperfusion but does not alter myocardial contractile function in the area at risk.

Topics: Acetylcholine; Animals; Arteries; Coronary Vessels; Endothelin-1; Endothelium, Vascular; Guanidines; Heart; Male; Myocardial Stunning; Protein Isoforms; Rats; Rats, Sprague-Dawley; Reference Values; Sodium-Hydrogen Exchangers; Sulfones; Vascular Resistance; Vasoconstriction; Vasodilation; Vasodilator Agents

The role of Na(+)/H(+) exchange in endothelin-1 (ET-1)-induced increases in Ca(2+) transients and cell shortening was studied in rabbit ventricular myocytes loaded with indo-1/AM. Selective inhibitors of Na(+)/H(+) exchange HOE642 (4-isopropyl-3-methyl-sulphonylbenzoyl guanidine methanesulphonate) and KB-R9032 (N-(4-isopropyl-2,2-dimethyl-3-oxo-3, 4-dihydro-2H-benzo-[1,4]oxazine-6-carbonyl) guanidine methanesulphonate) were used as pharmacological tools for the analysis. ET-1 at 0.1 nM induced an increase in Ca(2+) transients by 45.6%, while it increased cell shortening by 109.6%. For a given increase in cell shortening, the ET-1-induced increase in Ca(2+) transients was much smaller than that induced by isoprenaline (ISO, 10 nM). Pretreatment with HOE642 and KB-R9032 (1 microM) inhibited the increase in cell shortening induced by 0.1 nM ET-1 by 51 and 65. 4%, respectively, without a significant alteration of ET-1-induced increase in Ca(2+) transients. HOE642 and KB-R9032 did not affect baseline levels of cell shortening and peak Ca(2+) transients, and the effects of ISO (10 nM). These results indicate that activation of Na(+)/H(+) exchange by ET-1 may play an important role in the positive inotropic effect and the ET-1-induced increase in myofilament Ca(2+) sensitivity in rabbit ventricular myocytes.

Topics: Animals; Anti-Arrhythmia Agents; Calcium Signaling; Cardiotonic Agents; Endothelin-1; Guanidines; Heart Ventricles; In Vitro Techniques; Indoles; Isoproterenol; Male; Myocardium; Oxazines; Rabbits; Sodium-Hydrogen Exchangers; Sulfones