Cicletanine

The function of the endothelial isoform of nitric oxide synthase (eNOS) and production of nitric oxide (NO) is altered in a number of disease states. Pharmacological approaches to enhancing NO synthesis and thus perhaps endothelial function could have substantial benefits in patients. We analyzed the effect of cicletanine, a synthetic pyridine with potent vasodilatory characteristics, on eNOS function and NO production in normal (liver) and injured rat sinusoidal endothelial cells, and we studied the effect of cicletanine-induced NO on stellate cell contraction and portal pressure in an in vivo model of liver injury. Sinusoidal endothelial cells were isolated from normal and injured rat livers. After exposure to cicletanine, eNOS phosphorylation, NO synthesis, and the signaling pathway regulating eNOS activation were measured. Cicletanine led to an increase in eNOS (Ser1177) phosphorylation, cytochrome c reductase activity, l-arginine conversion to l-citrulline, as well as NO production. The mechanism of the effect of cicletanine appeared to be via the protein kinase B (Akt) and MAP kinase/Erk signaling pathways. Additionally, cicletanine improved NO synthesis in injured sinusoidal endothelial cells. NO production induced by cicletanine in sinusoidal endothelial cells increased protein kinase G (PKG) activity as well as relaxation of stellate cells. Finally, administration of cicletanine to mice with portal hypertension induced by bile duct ligation led to reduction of portal pressure. The data indicate that cicletanine might improve eNOS activity in injured sinusoidal endothelial cells and likely activates hepatic stellate cell NO/PKG signaling. It raises the possibility that cicletanine could improve intrahepatic vascular function in portal hypertensive patients.

Antihypertensive drugs from the thiazide diuretic drug class have been shown to reduce mortality and cardiovascular morbidity. Loop diuretics are indicated and used as antihypertensive drugs but a systematic review of their blood pressure lowering efficacy or effectiveness in terms of reducing cardiovascular mortality or morbidity from randomized controlled trial evidence has not been conducted.

To determine the dose related decrease in systolic and/or diastolic blood pressure as well as adverse events leading to patient withdrawal and adverse biochemical effects (serum potassium, uric acid, creatinine, glucose and lipids profile) due to loop diuretics versus placebo control in the treatment of patients with primary hypertension.

Medline (1946-February 2012), EMBASE (1974-February 2012), CENTRAL (issue 2, 2012) and bibliographic citations were searched.

Double blind randomized placebo controlled trials of at least 3 weeks duration comparing loop diuretic with a placebo in patients with primary hypertension defined as BP >140/90 mmHg at baseline were included.

Two authors independently assessed the risk of bias and extracted data. Weighted mean difference and a fixed effects model were used to combine continuous outcome data. The drop outs due to adverse effects was analysed using relative risk ratio.

Nine trials evaluated the dose-related blood pressure lowering efficacy of five drugs within the loop diuretics class (furosemide 40 to 60mg, cicletanine 100 to 150 mg, piretanide 3 to 6 mg, indacrinone enantiomer -2.5 to -10.0/+80 mg and etozolin 200 mg) in 460 patients with baseline blood pressure of 162/103 mmHg for a mean duration of 8.8 weeks. The best estimate of systolic/diastolic blood pressure lowering efficacy of loop diuretics was -7.9 (-10.5, -5.4) mmHg/ -4.4 (-5.6, -2.8) mmHg . Withdrawals due to adverse effects and serum biochemical changes did not show a significant difference.The 2012 updated search resulted in no additional new trials meeting the minimum inclusion criteria.

Based on the limited number of published RCTs, the systolic/diastolic blood pressure lowering effect of loop diuretics is modest (-8/-4 mmHg) and is likely an overestimate due to the high risk of bias in the included studies. There are no clinically meaningful BP lowering differences between different drugs within the loop diuretic class. The dose ranging effects of loop diuretics could not be evaluated. The review did not provide a good estimate of the incidence of harms associated with loop diuretics because of the short duration of the trials and the lack of reporting of adverse effects in many of the trials.