Diazoxide

Diazoxide is an ATP-sensitive potassium channel activator ; can be used to treat hyperinsulinism.

In Vitro:Diazoxide has a number of physiological effects, including lowering the blood pressure and rectifying hypoglycemia. Diazoxide has powerful protective properties against cardiac ischemia[1].Diazoxide could protect NSC-34 neurons against the main sources of neurodegenerative damage. Diazoxide increases Nrf2 nuclear translocation in NSC-34 motoneurons and prevents endogenous oxidative damage[2].

In Vivo:Diazoxide attenuates postresuscitation brain injury, protects mitochondrial function, inhibits brain cell apoptosis, and activates the PKC pathway by opening mitoKATP channels[3]. Treatment with diazoxide in wild-type mice decreases intraocular pressure (IOP) by 21.5±3.2% with an absolute IOP reduction of 3.9 ± 0.6 mm Hg[4].

References:
[1]. Coetzee WA, et al. Multiplicity of effectors of the cardioprotective agent, diazoxide. Pharmacol Ther. 2013 Nov;140(2):167-75. [2]. Virgili N, et al. K(ATP) channel opener diazoxide prevents neurodegeneration: a new mechanism of action viaantioxidative pathway activation. PLoS One. 2013 Sep 11;8(9):e75189. [3]. Wu H, et al. Diazoxide Attenuates Postresuscitation Brain Injury in a Rat Model of Asphyxial Cardiac Arrest by Opening Mitochondrial ATP-Sensitive Potassium Channels. Biomed Res Int. 2016;2016:1253842. [4]. Chowdhury UR, et al. ATP-sensitive potassium (K(ATP)) channel openers diazoxide and nicorandil lower intraocular pressure in vivo. Invest Ophthalmol Vis Sci. 2013 Jul 22;54(7):4892-9.

Diazoxide prevents reactive oxygen species and mitochondrial damage, leading to anti-hypertrophic effects.[Pubmed:27867086]

Chem Biol Interact. 2017 Jan 5;261:50-55.

Pathological cardiac hypertrophy is characterized by wall thickening or chamber enlargement of the heart in response to pressure or volume overload, respectively. This condition will, initially, improve the organ contractile function, but if sustained will render dysfunctional mitochondria and oxidative stress. Mitochondrial ATP-sensitive K(+) channels (mitoKATP) modulate the redox status of the cell and protect against several cardiac insults. Here, we tested the hypothesis that mitoKATP opening (using Diazoxide) will avoid isoproterenol-induced cardiac hypertrophy in vivo by decreasing reactive oxygen species (ROS) production and mitochondrial Ca(2+)-induced swelling. To induce cardiac hypertrophy, Swiss mice were treated intraperitoneally with isoproterenol (30 mg/kg/day) for 8 days. Diazoxide (5 mg/kg/day) was used to open mitoKATP and 5-hydroxydecanoate (5 mg/kg/day) was administrated as a mitoKATP blocker. Isoproterenol-treated mice had elevated heart weight/tibia length ratios and increased myocyte cross-sectional areas. Additionally, hypertrophic hearts produced higher levels of H2O2 and had lower glutathione peroxidase activity. In contrast, mitoKATP opening with Diazoxide blocked all isoproterenol effects in a manner reversed by 5-hydroxydecanoate. Isolated mitochondria from Isoproterenol-induced hypertrophic hearts had increased susceptibility to Ca(2+)-induced swelling secondary to mitochondrial permeability transition pore opening. MitokATP opening was accompanied by lower Ca(2+)-induced mitochondrial swelling, an effect blocked by 5-hydroxydecanoate. Our results suggest that mitoKATP opening negatively regulates cardiac hypertrophy by avoiding oxidative impairment and mitochondrial damage.

Effects of diazoxide in experimental acute necrotizing pancreatitis.[Pubmed:28273237]

Clinics (Sao Paulo). 2017 Feb 1;72(2):125-129.

OBJECTIVE:: We aimed to assess the effects of Diazoxide on the mortality, pancreatic injury, and inflammatory response in an experimental model of acute pancreatitis. METHODS:: Male Wistar rats (200-400 g) were divided randomly into two groups. Fifteen minutes before surgery, animals received physiological (0.9%) saline (3 mL/kg) (control group) or 45 mg/kg Diazoxide (treatment group) via the intravenous route. Acute pancreatitis was induced by injection of 2.5% sodium taurocholate via the biliopancreatic duct. Mortality (n=38) was observed for 72 h and analyzed by the Mantel-Cox Log-rank test. To study pancreatic lesions and systemic inflammation, rats (10 from each group) were killed 3 h after acute pancreatitis induction; ascites volume was measured and blood as well as pancreases were collected. Pancreatic injury was assessed according to Schmidt's scale. Cytokine expression in plasma was evaluated by the multiplex method. RESULTS:: Mortality at 72 h was 33% in the control group and 60% in the treatment group (p=0.07). Ascites volumes and plasma levels of cytokines between groups were similar. No difference was observed in edema or infiltration of inflammatory cells in pancreatic tissues from either group. However, necrosis of acinar cells was lower in the treatment group compared to the control group (3.5 vs. 3.75, p=0.015). CONCLUSIONS:: Treatment with Diazoxide can reduce necrosis of acinar cells in an experimental model of acute pancreatitis, but does not affect the inflammatory response or mortality after 72 h.

A novel mutation of ABCC8 gene in a patient with diazoxide-unresponsive congenital hyperinsulinism.[Pubmed:28018462]

Korean J Pediatr. 2016 Nov;59(Suppl 1):S116-S120.

Congenital hyperinsulinism (CHI) is a rare condition that can cause irreversible brain damage during the neonatal period owing to the associated hypoglycemia. Hypoglycemia in CHI occurs secondary to the dysregulation of insulin secretion. CHI has been established as a genetic disorder of islet-cell hyperplasia, associated with a mutation of the ABCC8 or KCNJ11 genes, which encode the sulfonylurea receptor 1 and the inward rectifying potassium channel (Kir6.2) subunit of the ATP-sensitive potassium channel, respectively. We report the case of a female newborn infant who presented with repetitive seizures and episodes of apnea after birth, because of hypoglycemia. Investigations revealed hypoglycemia with hyperinsulinemia, but no ketone bodies, and a low level of free fatty acids. High dose glucose infusion, enteral feeding, and medications could not maintain the patient's serum glucose level. Genetic testing revealed a new variation of ABCC8 mutation. Therefore, we report this case of CHI caused by a novel mutation of ABCC8 in a half-Korean newborn infant with Diazoxide-unresponsive hyperinsulinemic hypoglycemia.

Clinical presentation and treatment response to diazoxide in two siblings with congenital hyperinsulinism as a result of a novel compound heterozygous ABCC8 missense mutation.[Pubmed:28328534]

J Pediatr Endocrinol Metab. 2017 Apr 1;30(4):471-474.

BACKGROUND: Congenital hyperinsulinism (CHI) can present with considerable clinical heterogeneity which may be due to differences in the underlying genetic etiology. We present two siblings with hyperinsulinaemic hypoglycaemia (HH) and marked clinical heterogeneity caused by compound heterozygosity for the same two novel ABCC8 mutations. CASE PRESENTATION: The index patient is a 3-year-old boy with hypoglycaemic episodes presenting on the first day of life. HH was diagnosed and treatment with intravenous glucose and Diazoxide was initiated. Currently he has normal physical and neurological development, with occasional hypoglycaemic episodes detected following continuous fasting on treatment with Diazoxide. The first-born 8-year-old sibling experienced severe postnatal hypoglycaemia, generalised seizures and severe brain damage despite Diazoxide treatment. The latter was stopped at 6-months of age with no further registered hypoglycaemia. Genetic testing showed that both children were compound heterozygotes for two novel ABCC8 missense mutations p.I60N (c.179T>A) and p.G1555V (c.4664G>T). CONCLUSIONS: These ABCC8 missense mutations warrant further studies mainly because of the variable clinical presentation and treatment response.

Diazoxide acts more as a PKC-epsilon activator, and indirectly activates the mitochondrial K(ATP) channel conferring cardioprotection against hypoxic injury.[Pubmed:17043673]

Br J Pharmacol. 2006 Dec;149(8):1059-70.

BACKGROUND AND PURPOSE: Diazoxide, a well-known opener of the mitochondrial ATP-sensitive potassium (mitoK(ATP)) channel, has been demonstrated to exert cardioprotective effect against ischemic injury through the mitoK(ATP) channel and protein kinase C (PKC). We aimed to clarify the role of PKC isoforms and the relationship between the PKC isoforms and the mitoK(ATP) channel in Diazoxide-induced cardioprotection. EXPERIMENTAL APPROACH: In H9c2 cells and neonatal rat cardiomyocytes, PKC-epsilon activation was examined by Western blotting and kinase assay. Flavoprotein fluorescence, mitochondrial Ca(2+) and mitochondrial membrane potential were measured by confocal microscopy. Cell death was determined by TUNEL assay. KEY RESULTS: Diazoxide (100 microM) induced translocation of PKC-epsilon from the cytosolic to the mitochondrial fraction. Specific blockade of PKC-epsilon by either epsilonV1-2 or dominant negative mutant PKC-epsilon (PKC-epsilon KR) abolished the anti-apoptotic effect of Diazoxide. Diazoxide-induced flavoprotein oxidation was inhibited by either epsilonV1-2 or PKC-epsilon KR transfection. Treatment with 5-hydroxydecanoate (5-HD) did not affect translocation and activation of PKC-epsilon induced by Diazoxide. Transfection with wild type PKC-epsilon mimicked the flavoprotein-oxidizing effect of Diazoxide, and this effect was completely blocked by epsilonV1-2 or 5-HD. Diazoxide prevented the increase in mitochondrial Ca(2+), mitochondrial depolarization and cytochrome c release induced by hypoxia and all these effects of Diazoxide were blocked by epsilonV1-2 or 5-HD. CONCLUSIONS AND IMPLICATIONS: Diazoxide induced isoform-specific translocation of PKC-epsilon as an upstream signaling molecule for the mitoK(ATP) channel, rendering cardiomyocytes resistant to hypoxic injury through inhibition of the mitochondrial death pathway.

Diazoxide blocks glutamate desensitization and prolongs excitatory postsynaptic currents in rat hippocampal neurons.[Pubmed:1302270]

J Physiol. 1992 Dec;458:409-23.

1. The effects of Diazoxide (DZ) on synaptic transmission and upon responses to exogenously applied glutamate agonists were examined in cultured hippocampal neurons. 2. DZ reversibly increased the peak amplitude of evoked excitatory postsynaptic currents (EPSCs) to 150 +/- 100% of control and prolonged the EPSC decay time constant (tau) from 5.9 +/- 1.2 ms to 14 +/- 6.2 ms (240% of control). 3. Peak and steady-state glutamate (Glu) and quisqualate (QA) currents activated by exogenous application were dramatically increased by DZ at concentrations which did not influence N-methyl-D-aspartate (NMDA), kainate (KA), or GABA currents. These effects were rapidly and completely reversible. Active and passive membrane properties were unaffected by DZ. 4. Inhibitory postsynaptic currents (IPSCs) were unaffected by the same DZ concentrations. 5. These experiments indicate that desensitization plays an important role in terminating excitatory transmission between mammalian central neurons. DZ and perhaps related compounds will ultimately help us identify the regions of the AMPA/KA receptor responsible for desensitization.

Opposite effects of tolbutamide and diazoxide on the ATP-dependent K+ channel in mouse pancreatic beta-cells.[Pubmed:2431383]

Pflugers Arch. 1986 Nov;407(5):493-9.

The influence of the antidiabetic sulphonylurea tolbutamide on K+ channels of mouse pancreatic beta-cells was investigated using different configurations of the patch clamp technique. The dominant channel in resting cells is a K+ channel with a single-channel conductance of 60 pS that is inhibited by intracellular ATP or, in intact cells, by stimulation with glucose. In isolated patches of beta-cells membrane, this channel was blocked by tolbutamide (0.1 mM) when applied to either the intracellular or extracellular side of the membrane. The dose-dependence of the tolbutamide-induced block was obtained from whole-cell experiments and revealed that 50% inhibition was attained at approximately 7 microM. In cell-attached patches low concentrations of glucose augmented the action of tolbutamide. Thus, the simultaneous presence of 5 mM glucose and 0.1 mM tolbutamide abolished channel activity and induced action potentials. These were not produced when either of these substances was added alone at these concentrations. The inhibitory action of tolbutamide or glucose on the K+ channel was counteracted by the hyperglycaemic sulphonamide Diazoxide (0.4 mM). Tolbutamide (1 mM) did not affect Ca2+-dependent K+ channels. It is concluded that the hypo- and hyperglycaemic properties of tolbutamide and Diazoxide reflect their ability to induce the closure or opening, respectively, of ATP-regulated K+ channels.