Apoptosis and Mitochondrial Damage in INS-1 Cells Treated with Alloxan.

Abstract

A variety of mechanisms have been identified as responsible for the onset of diabetes mellitus. Alloxan shows a selective cytotoxicity on pancreatic b-cells and thus causes insulin-dependent (type I) diabetes mellitus. Although the mechanism of alloxan cytotoxicity is not yet clearly understood, several researchers 1,2) demonstrated that the diabetogenic action was initiated by the generation of reactive oxygen species (ROS). Alloxan is a mild oxidant and is easily reduced to alloxan radicals (A· Ϫ ) by GSH or ascorbic acid. 3) Our previous study 4) demonstrated that A· Ϫ can directly reduce O 2 and ferric ions to superoxide anion radical (O 2 · Ϫ ) and ferrous ions, respectively. The extreme and indiscriminate reactivity of ROS could easily explain the killing of b-cells by alloxan. In support of this hypothesis alloxan diabetes is prevented by HO · scavengers, 5-7) superoxide dismutase (SOD) 2) and vitamin E. 8) In addition, on the basis of in vivo and in vitro studies using rats and isolated islet cells, respectively, it was proposed that the process of alloxan toxicity involved the generation of HO · by which the DNA strands break of pancreatic islets is attacked to produce. 9-11) These findings indicate that DNA strand breaks are involved in the events of alloxan-diabetogenesis. However, the complex sequence of events that eventually leads to the DNA strand breaks and death of pancreatic b-cells in alloxan diabetes mellitus is not clear.Cell death might occur by one of two fundamental processes, necrosis or apoptosis. The biochemical hallmarks of apoptosis are the distribution of phosphatidylserine (PS) at the external surface of the plasma membrane (PS exposure) in the early stages, and the cleavage of chromosomal DNA into nucleosomal units, which appears to be the final blow in the cell death process. Recent studies have shown that different trigger such as IL-1b 12) and streptozotocin 13) can induce apoptosis in pancreatic b-cells. Although detailed studies indicate that alloxan can induce insulin-dependent diabetes mellitus, nothing is known about apoptotic action or the sequence of cellular events of alloxan on the b-cells.According to current understanding, mitochondrial damage seems to occur in the early phase of apoptosis and to participate in the control of apoptosis. 14,15) Release of cytochrome c and apoptosis induced factor from mitochondria into cytoplasm during mitochondrial permeability transition cause to active caspase family, leading to the completion of apoptosis. 15,16) Isolated liver mitochondria incubated with alloxan alters respiration, decreases in the concentration of adenine nucleotides, causes Ca 2ϩ release, and changes in the Dy, 17,18) indicating that alloxan directly induces the mitochondrial damage. However, the relationship between diabetes, apoptosis and mitochondrial damage has remained elusive.INS-1 cells were established by X-ray-induced rat transplantable insulinoma, and have retained the similar ability of glucose-stimulated insulin release of native b-cells. 19) INS-1 ...

Suppressive effects of electrolyzed reduced water on alloxan-induced apoptosis and type 1 diabetes mellitus

“…Our interpretation of the higher insulin levels is that b-cell loss by apoptosis is lowered by scavenging ALX-induced ROS, consequently retarding DNA fragmentation and, thus delaying b-cell loss. Sakurai et al also reported that vitamin E and butylated hydroxyanisol significantly prevented the inhibition of glucose-stimulated insulin release by treatment with 0.3 mM ALX (Sakurai et al 2001). Other agents, including Ganoderma lucidum polysaccharides isolated from the fruiting body of a medicinal mushroom (Zhang et al 2003) and red grape seeds proanthocyanidins (El-Alfy et al 2005) are also reported to function as free radical scavengers in ALX-induced diabetic animals.…”

“…In turn, such oxidative stress, contributes to b-cell dysfunction and death resulting in the development of diabetes mellitus (Eizirik and Darville 2001;Curtin et al 2002). Taken together, the data indicate that apoptosis is the main mode of pancreatic b-cell destruction (Cnop et al 2005;Kay et al 2000;Jörns et al 2005;Sakurai et al 2001). It is known that DNA fragmentation is preceded by single-strand nicking in apoptosis.…”

Anti-diabetic activity of crude <i>Pistacia lentiscus</i> in alloxan-induced diabetes in rats

“…Alloxan induced diabetes produces selective cytotoxicity in β-cells of pancreas through the generation of free radicals resulting in reduced synthesis and release of insulin (Sakurai et al, 2001). In acute study, mastic gum showed significant decrease in blood glucose that was comparable to glibenclamide by rapid normalization of blood glucose levels while high glucose level was observed in alloxan-treated groups throughout the total time period of study.…”

<i>Zostera noltii</i> extract lowers blood glucose and restores vascular function in diabetic rats

“…As is known, alloxan increases production of reactive oxygen species (ROS) leading to cytotoxicity in pancreatic β-cells, and thereby inhibits insulin activity while affecting major organs and haemopoietic system (Sakurai et al, 2001;Sabu et al, 2002). Additionally, alloxan impairs endothe -lium-dependent vasorelaxation and increases contractile responses to agonists such as phenylephrine and 5-HT (Gokce and Haznedaroglu, 2008).…”