Evaluation of cytokines and structural proteins to analyze the pathology of febrile central nervous system disease

ZBP1 and heatstroke

Heatstroke, which is associated with circulatory failure and multiple organ dysfunction, is a heat stress-induced life-threatening condition characterized by a raised core body temperature and central nervous system dysfunction. As global warming continues to worsen, heatstroke is expected to become the leading cause of death globally. Despite the severity of this condition, the detailed mechanisms that underlie the pathogenesis of heatstroke still remain largely unknown. Z-DNA-binding protein 1 (ZBP1), also referred to as DNA-dependent activator of IFN-regulatory factors (DAI) and DLM-1, was initially identified as a tumor-associated and interferon (IFN)-inducible protein, but has recently been reported to be a Z-nucleic acid sensor that regulates cell death and inflammation; however, its biological function is not yet fully understood. In the present study, a brief review of the main regulators is presented, in which the Z-nucleic acid sensor ZBP1 was identified to be a significant factor in regulating the pathological characteristics of heatstroke through ZBP1-dependent signaling. Thus, the lethal mechanism of heatstroke is revealed, in addition to a second function of ZBP1 other than as a nucleic acid sensor.

Central nervous system stimulants promote nerve cell death under continuous hypoxia

Intake of central nervous system (CNS) stimulants causes hypoxia and brain edema, which results in nerve cell death. However, no study has yet investigated the direct and continuous effects on nerve cells of CNS stimulants under hypoxia. Thus, based on autopsy cases, the effects of CNS stimulant drugs on the CNS were examined. The pathological changes in cultured nerve cells when various CNS stimulants were added under a hypoxic condition were also investigated. Five groups (Group A, stimulants; Group B, stimulants with psychiatric drugs; Group C, caffeine; Group D, psychiatric drugs; and Group E, no drugs) according to the detected drugs in autopsy cases were compared, and brain edema was evaluated using morphological findings. Furthermore, the number of dead cultured nerve cells was counted after the addition of drugs (4-aminopyridine (4-AP), caffeine, and ephedrine) under hypoxia (3% O2). Staining with anti-receptor-interacting protein 3 (RIP3) and other associated stains was also performed to investigate the neuronal changes in the brain. Group A showed significantly more brain edema than the other groups. In the culture experiments, the ratio of nerve cell death after the addition of 4-AP was the highest in the hypoxic condition. Groups with stimulants detected were stained more strongly by RIP3 immunostaining than by other staining. Addition of stimulants to cultured nerve cells in a persistent hypoxic condition led to severe cytotoxicity and nerve cell death. These findings suggest that necroptosis is involved in nerve cell death due to the addition of CNS stimulants in the hypoxic condition.

Central Nervous System Stimulants Limit Caffeine Transport at the Blood-Cerebrospinal Fluid Barrier

Caffeine, a common ingredient in energy drinks, crosses the blood-brain barrier easily, but the kinetics of caffeine across the blood-cerebrospinal fluid barrier (BCSFB) has not been investigated. Therefore, 127 autopsy cases (Group A, 30 patients, stimulant-detected group; and Group B, 97 patients, no stimulant detected group) were examined. In addition, a BCSFB model was constructed using human vascular endothelial cells and human choroid plexus epithelial cells separated by a filter, and the kinetics of caffeine in the BCSFB and the effects of 4-aminopyridine (4-AP), a neuroexcitatory agent, were studied. Caffeine concentrations in right heart blood (Rs) and cerebrospinal fluid (CSF) were compared in the autopsy cases: caffeine concentrations were higher in Rs than CSF in Group A compared to Group B. In the BCSFB model, caffeine and 4-AP were added to the upper layer, and the concentration in the lower layer of choroid plexus epithelial cells was measured. The CSF caffeine concentration was suppressed, depending on the 4-AP concentration. Histomorphological examination suggested that choroid plexus epithelial cells were involved in inhibiting the efflux of caffeine to the CSF. Thus, the simultaneous presence of stimulants and caffeine inhibits caffeine transfer across the BCSFB.