Inhibition of autophagy enhances DNA damage-induced apoptosis by disrupting CHK1-dependent S phase arrest.

DNA damage has been shown to induce autophagy, but the role of autophagy in the DNA damage response and cell fate is not fully understood. BO-1012, a bifunctional alkylating derivative of 3a-aza-cyclopenta[a]indene, is a potent DNA interstrand cross-linking agent with anticancer activity. In this study, BO-1012 was found to reduce DNA synthesis, inhibit S phase progression, and induce phosphorylation of histone H2AX on serine 139 (γH2AX) exclusively in S phase cells. Both CHK1 and CHK2 were phosphorylated in response to BO-1012 treatment, but only depletion of CHK1, but not CHK2, impaired BO-1012-induced S phase arrest and facilitated the entry of γH2AX-positive cells into G2 phase. CHK1 depletion also significantly enhanced BO-1012-induced cell death and apoptosis. These results indicate that BO-1012-induced S phase arrest is a CHK1-dependent pro-survival response. BO-1012 also resulted in marked induction of acidic vesicular organelle (AVO) formation and microtubule-associated protein 1 light chain 3 (LC3) processing and redistribution, features characteristic of autophagy. Depletion of ATG7 or co-treatment of cells with BO-1012 and either 3-methyladenine or bafilomycin A1, two inhibitors of autophagy, not only reduced CHK1 phosphorylation and disrupted S phase arrest, but also increased cleavage of caspase-9 and PARP, and cell death. These results suggest that cells initiate S phase arrest and autophagy as pro-survival responses to BO-1012-induced DNA damage, and that suppression of autophagy enhances BO-1012-induced apoptosis via disruption of CHK1-dependent S phase arrest.

The role of melatonin and melatonin receptor agonist in the prevention of sleep disturbances and delirium in intensive care unit - a clinical review.

AIM: The intensive care unit (ICU) environment contributes to the development of sleep disturbances. Sleep disturbances, sleep fragmentation, and multiple awakening episodes lead to the circadian rhythm disorder, which increases the risk of delirium. Melatonin and melatonin receptor agonist is widely used agent in the therapy of sleep disturbances. However, there is also some for its efficacy in ICU delirium. Enteral melatonin and ramelteon supplementation eliminates (partially) the delirium inducing factors. METHODS: PubMed/MEDLINE, OVID, Embase, Cochrane Library, and Web of Science databases were searched using adequate key words. We reviewed the literature on the role of melatonin and ramelteon in the prevention of sleep disturbances and delirium in intensive care units and analysed the methods of melatonin therapy in an ICU setting. Review followed the PRISMA statement. A review written protocol was not drafted. RESULTS: Originally 380 studies were searched in five scientific databases. After rejecting the duplicate results, 125 results were obtained. Finally, 10 scientific studies were included in the review. In selected articles, the leading topics analysed were the role of melatonin and ramelteon in the prevention of delirium and sleep disorders. In addition, the noted effect of therapy with these agents on reducing the ventilation time of mechanical time and the demand for psychoactive substances in the ICU environment. CONCLUSION: Reduction of either the incidence or the severity of delirium course is possible by eliminating its risk factors. Risk factors are directly related to sleep disorders. To reduce the problem, therefore, a holistic approach to the source is necessary. The efficacy of melatonin therapy in an ICU setting requires confirmation in studies including a greater number of participants as the impact of melatonin on these factors is yet to be fully elucidated. However, the prognosis is predictive because this concept provides patients with a minimally invasive and natural form of therapy.