Factors That Affect Continuation of Antipsychotic Long-Acting Injections.

Long-acting injection (LAI) is a drug administration method that reduces symptoms and prevents recurrence or relapse of schizophrenia. We examined factors related to the continuation of LAI treatment. The study population included patients with schizophrenia who were undergoing LAI treatment involving risperidone, paliperidone, or aripiprazole at Fujita Health University Hospital between October 2009 and June 2017. We assessed the continuation rate of LAI treatment at six months, and collected patient characteristics such as medication history. Furthermore, we classified patients into two clusters according to the reason for introducing LAI based on a previous study (Prog. Neuropsychopharmacol. Biol. Psychiatry, 2008, Heres et al.). The study included 82 patients (mean age, 44.9 ± 15.0 years); the continuation rate of LAI after six months was 63.4%. Factors that affected LAI continuation included cluster II [adjusted odds ratio (OR): 5.74, p = 0.017], switching from the same component as LAI (adjusted OR: 7.13, p < 0.001), and diazepam conversion rate (adjusted OR: 0.88, p < 0.001). LAI significantly improved the continuation rate of treatment in the patient group belonging to cluster II. Furthermore, based on other factors and reasons for discontinuation, LAI should be preferably commenced in patients with a more stable condition.

Differences in intracellular mobile zinc levels affect susceptibility to plasma-activated medium-induced cytotoxicity.

There is growing evidence that plasma-activated medium (PAM), which is prepared by non-thermal plasma (NTP) irradiation of cell-free medium, is a beneficial tool for cancer therapy. PAM has been reported to preferentially kill cancer cells; however, its mechanism is not fully understood. Since PAM contains reactive oxygen species (ROS) and reactive nitrogen species, the anti-cancer effects of PAM are thought to be attributed to oxidative stress induced by these reactive molecules. Oxidative stress has been shown to release zinc (Zn2+) from intracellular Zn2+ stores and provoke Zn2+-dependent cell death. We have previously demonstrated that intracellular free Zn2+ plays a critical role in PAM-induced cell death in human neuroblastoma SH-SY5Y cells. In this study, we found that normal human fibroblasts were less susceptible to PAM cytotoxicity compared with SH-SY5Y cells. PAM decreased intracellular NAD+ levels in both cells, whereas the depletion of ATP and mitochondrial ROS generation was hardly observed in fibroblasts. Intracellular mobile Zn2+ contents of fibroblasts were lower than those of SH-SY5Y cells. PAM suppressed the activity of aconitase, which is a tricarboxylic acid cycle enzyme, only in SH-SY5Y cells, and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), a Zn2+ chelator, counteracted the suppression. The combination treatment with PAM and Zn2+ augmented PAM-induced ATP depletion, mitochondrial ROS generation, and cytotoxicity in fibroblasts. These findings suggest the possibility that cells with high intracellular mobile Zn2+ are susceptible to PAM cytotoxicity. Therefore, we concluded that the differences in mobile Zn2+ levels affect PAM-induced cellular responses.

Plasma-activated medium-induced intracellular zinc liberation causes death of SH-SY5Y cells.

Plasma is an ionized gas consisting of ions, electrons, free radicals, neutral particles, and photons. Plasma-activated medium (PAM), which is prepared by the irradiation of cell-free medium with non-thermal atmospheric pressure plasma, induces cell death in various types of cancer cell. Since PAM contains reactive oxygen species (ROS), its anti-cancer effects are thought to be attributable to oxidative stress. Meanwhile, oxidative stress has been shown to induce the liberation of zinc (Zn(2+)) from intracellular Zn(2+) stores and to provoke Zn(2+)-dependent cell death. In this study, we thus examined whether Zn(2+) is involved in PAM-induced cell death using human neuroblastoma SH-SY5Y cells. Exposure to PAM triggered cell death in SH-SY5Y cells. The cell-permeable Zn(2+) chelator N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN) protected against PAM-induced cell death. Zn(2+) imaging using the fluorescent Zn(2+) probe FluoZin-3 revealed that PAM elicited a rise of intracellular free Zn(2+). In addition, PAM stimulated PARP-1 activation, mitochondrial ROS generation, and the depletion of intracellular NAD(+) and ATP. These findings suggest that PAM-induced PARP-1 activation causes energy supply exhaustion. Moreover, TPEN suppressed all of these events elicited by PAM. Taken together, we demonstrated here that Zn(2+) released from intracellular Zn(2+) stores serves as a key mediator of PAM-induced cell death in SH-SY5Y cells.