Two drugs are available for the treatment of balding in men. Minoxidil, a topical product, is available without a prescription in two strengths. Finasteride is a prescription drug taken orally once daily. Both agents are modestly effective in maintaining (and sometimes regrowing) hair that is lost as a result of androgenic alopecia. The vertex of the scalp is the area that is most likely to respond to treatment, with little or no hair regrowth occurring on the anterior scalp or at the hairline. Side effects of these medications are minimal, making them suitable treatments for this benign but psychologically disruptive condition. (+info)
KATP channels regulate mitogenically induced proliferation in primary rat hepatocytes and human liver cell lines. Implications for liver growth control and potential therapeutic targeting.
To determine whether K(ATP) channels control liver growth, we used primary rat hepatocytes and several human cancer cell lines for assays. K(ATP) channel openers (minoxidil, cromakalim, and pinacidil) increased cellular DNA synthesis, whereas K(ATP) channel blockers (quinidine and glibenclamide) attenuated DNA synthesis. The channel inhibitor glibenclamide decreased the clonogenicity of HepG2 cells without inducing cytotoxicity or apoptosis. To demonstrate the specificity of drugs for K(+) channels, whole-cell patch-clamp recordings were made. Hepatocytes revealed K(+) currents with K(ATP) channel properties. These K(+) currents were augmented by minoxidil and pinacidil and attenuated by glibenclamide as well as tetraethylammonium, in agreement with established responses of K(ATP) channels. Reverse transcription of total cellular RNA followed by polymerase chain reaction showed expression of K(ATP) channel-specific subunits in rat hepatocytes and human liver cell lines. Calcium fluxes were unperturbed in glibenclamide-treated HepG2 cells and primary rat hepatocytes following induction with ATP and hepatocyte growth factor, respectively, suggesting that the effect of K(ATP) channel activity upon hepatocyte proliferation was not simply due to indirect modulation of intracellular calcium. The regulation of mitogen-related hepatocyte proliferation by K(ATP) channels advances our insights into liver growth control. The findings have implications in mechanisms concerning liver development, regeneration, and oncogenesis. (+info)
A case of acute myocardial infarction associated with topical use of minoxidil (RiUP) for treatment of baldness.
A 45-year-old Japanese man with paroxysmal atrial fibrillation (AF) developed acute anteroseptal myocardial infarction (MI). He had used 1% topical minoxidil (RiUP) once a day for 4 months before the onset of MI for treatment of baldness. Coronary angiography demonstrated severe stenosis at the proximal portion of the left anterior descending coronary artery with a tilling defect. Electrocardiographic monitoring revealed paroxysmal AF and sinus bradycardia with sinus arrests, suggestive of sick sinus syndrome. Topical minoxidil is now widely used for the treatment of male pattern baldness. Although it may be difficult to relate topical use of minoxidil to myocardial ischemia, a greater awareness of its toxicity will be necessary, and patients with cardiovascular disorders should be excluded from the therapy. (+info)
An abnormal Ca(2+) response in mutant sarcomere protein-mediated familial hypertrophic cardiomyopathy.
Dominant-negative sarcomere protein gene mutations cause familial hypertrophic cardiomyopathy (FHC), a disease characterized by left-ventricular hypertrophy, angina, and dyspnea that can result in sudden death. We report here that a murine model of FHC bearing a cardiac myosin heavy-chain gene missense mutation (alphaMHC(403/+)), when treated with calcineurin inhibitors or a K(+)-channel agonist, developed accentuated hypertrophy, worsened histopathology, and was at risk for early death. Despite distinct pharmacologic targets, each agent augmented diastolic Ca(2+) concentrations in wild-type cardiac myocytes; alphaMHC(403/+) myocytes failed to respond. Pretreatment with a Ca(2+)-channel antagonist abrogated diastolic Ca(2+) changes in wild-type myocytes and prevented the exaggerated hypertrophic response of treated alphaMHC(403/+) mice. We conclude that FHC-causing sarcomere protein gene mutations cause abnormal Ca(2+) responses that initiate a hypertrophic response. These data define an important Ca(2+)-dependent step in the pathway by which mutant sarcomere proteins trigger myocyte growth and remodel the heart, provide definitive evidence that environment influences progression of FHC, and suggest a rational therapeutic approach to this prevalent human disease. (+info)
Mortality after coronary artery occlusion in different models of cardiac hypertrophy in rats.
Chronic treatment with minoxidil induces cardiac trophic and sympathetic responses, which may increase the propensity for lethal arrhythmias. To test this hypothesis, acute coronary artery occlusion was performed in conscious normotensive rats treated for 2 or 5 weeks with minoxidil with the use of a 2-stage approach to cause a myocardial infarction. For comparison, rats with aortocaval (A-V) shunts and spontaneously hypertensive rats (SHR) were studied. Minoxidil increased left ventricular and right ventricular weights by 15% to 20%, and the A-V shunt increased these weights by 30% to 40%. In SHR, left ventricular weight was increased by 50%, and right ventricular weight was increased by 25%. In rats treated with minoxidil for 5 weeks, coronary artery occlusion caused a rapid and marked mortality, and 4 hours after myocardial infarction, only 18% of these rats were alive versus 61% of the control rats. In rats with the A-V shunt, coronary artery occlusion was also associated with increased mortality, and after 6 hours, 33% were still alive compared with 59% of the control rats. In contrast, SHR with marked hypertension and cardiac hypertrophy showed only a minor increase in mortality (survival rates were 53% versus 60% in SHR versus Wistar-Kyoto rats, respectively). Mortality was preceded by high arrhythmia scores, and ventricular fibrillation was the cause of death. Discontinuation of minoxidil for 1 week, sympathetic blockade with nadolol or clonidine, or blockade of the renin-angiotensin system with enalapril or losartan did not improve minoxidil-induced excess mortality. We conclude that ventricular stretch and other mechanisms (eg, cardiac vagal activity) in rats appear to be more potent than hypertension-induced left ventricular hypertrophy in predisposing for lethal arrhythmias in the setting of acute ischemia. (+info)
Reduction of potassium currents and phosphatidylinositol 3-kinase-dependent AKT phosphorylation by tumor necrosis factor-(alpha) rescues axotomized retinal ganglion cells from retrograde cell death in vivo.
Tumor-necrosis-factor-alpha (TNF-alpha) prevented secondary death of retinal ganglion cells (RGCs) after axotomy of the optic nerve in vivo. This RGC rescue was confirmed in vitro in a mixed retinal culture model. In accordance with our previous findings, TNF-alpha decreased outward potassium currents in RGCs. Antagonism of the TNF-alpha-induced decrease in outward potassium currents with the potassium channel opener minoxidilsulfate (as verified by electrophysiology) abolished neuroprotection. Western blot analysis revealed an upregulation of phospho-Akt as a consequence of TNF-alpha-induced potassium current reduction. Inhibition of the phosphatidylinositol 3-kinase-Akt pathway with wortmannin decreased TNF-alpha-promoted RGC survival. These data point to a functionally relevant cytokine-dependent neuroprotective signaling cascade in adult CNS neurons. (+info)
Control plasma renin activity and changes in sympathetic tone as determinants of minoxidil-induced increase in plasma renin activity.
A study was made of the possible mechanism(s) underlying minoxidil-induced increase in plasma renin activity (PRA). 10 patients with essential hypertension were treated with minoxidil and subsequently with a combination of minoxidil plus propranolol. Minoxidil lowered mean arterial pressure 31.6 plus or minus 3.3 mm Hg, mean plus or minus SEM. There was an associated increase in both PRA, 6.26 plus or minus 2.43 NG/ML/H, and heart rate, 21.4 plus or minus 2.7 beats/min. The changes in PRA and heart rate were positively correlated, r, 0.79. Addition of propranolol reduced mean arterial pressure by a further 10.1 plus or minus 1.5 mm Hg and returned heart rate to control levels. Propranolol reduced PRA significantly but not to control levels. Control PRA positively correlated with PRA on minoxidil, r, 0.97, and with PRA on minoxidil plus propranolol, r, 0.98. We conclude that control PRA is a major determinant of change in PRA with minoxidil. Minoxidil increased PRA by at least two mechanisms: (a) an adrenergic mechanism closely related to change in heart rate and blocked by propranolol, and (b) a mechanism(s) not sensitive to propranolol and possibly related to decrease in renal perfusion pressure. (+info)
The role of ATP-sensitive potassium channels in neutrophil migration and plasma exudation.
Neutrophil activation and migration during an inflammatory response is preceded or accompanied by plasma membrane electrical changes. Besides changes in calcium currents, neutrophils have a high permeability to potassium, mainly through potassium channels. However, the significance of potassium channels in neutrophil physiology is still unclear. Here, we show that the treatment of rats with the ATP-sensitive potassium channel blocker glibenclamide (4, 20, or 40 micromol/kg) dose dependently decreased carrageenan-, N-formyl-methionyl-leucyl-phenylalanine (fMLP)-, and lipopolysaccharide-induced neutrophil influx and fluid leakage into the interpleural space. On the other hand, minoxidil (an ATP-sensitive potassium channel opener; 25, 50, and 100 micromol/kg) increased both neutrophil influx and fluid leakage induced by a submaximal dose of carrageenan. In addition, in vitro human neutrophil chemotaxis induced by leukotriene B4 or fMLP (both 1 microM) was fully blocked by glibenclamide (10, 30, and 100 microM) or tetraethylammonium (a nonselective potassium channel blocker; 1, 3, and 10 mM). Thus, our results disclose the possibility that ATP-sensitive potassium channels may have a role in neutrophil migration and chemotaxis and plasma exudation in the inflammatory response. (+info)