Gene expression profiling of brain cortex microvessels may support brain vasodilation in acute liver failure rat models

Safety of Gliadel Implant for Malignant Glioma: Report of Postmarketing Surveillance in Japan

Clinical trial data of Carmustine implant (Gliadel Wafer) in Japanese patients with malignant glioma are limited; thus, we conducted a postmarketing surveillance study to evaluate the safety of Gliadel in real-world clinical practice in Japan. In this postmarketing surveillance study, all patients who received Gliadel placement for malignant glioma surgeries from its market launch (January 9, 2013) to July 10, 2013 were enrolled from 229 institutions using a central registration system. Up to eight wafers of Gliadel (containing 61.6 mg of carmustine) were used to cover the site of brain tumor resection intraoperatively according to the size and shape of the tumor resection cavity. The observation period lasted 3 months after Gliadel placement. Patients were followed up for 1 year postoperatively. Safety was assessed by the incidence of adverse events (AEs) and adverse drug reactions (ADRs). In total, 558 patients were included. Most patients (66.7%) received eight Gliadel wafers. The percentage of patients with ADRs was 35.7% (365 ADR episodes in 199 patients). Of the AEs of special interest, the most common were cerebral edema (22.2%, 124/558 patients), convulsion (9.9%, 55/558 patients), impaired healing (4.8%, 27/558 patients), and infection (3.4%, 19/558 patients). This first all-case postmarketing surveillance report of the safety of Gliadel in real-world clinical practice in Japan suggests that the risk of toxicity with Gliadel placement is relatively tolerable. The survival benefits of Gliadel placement should be evaluated and considered carefully by the clinician taking into account possible toxicities.

Decreased Expression and Uncoupling of Endothelial Nitric Oxide Synthase in the Cerebral Cortex of Rats with Thioacetamide-Induced Acute Liver Failure

Acute liver failure (ALF) is associated with deregulated nitric oxide (NO) signaling in the brain, which is one of the key molecular abnormalities leading to the neuropsychiatric disorder called hepatic encephalopathy (HE). This study focuses on the effect of ALF on the relatively unexplored endothelial NOS isoform (eNOS). The cerebral prefrontal cortices of rats with thioacetamide (TAA)-induced ALF showed decreased eNOS expression, which resulted in an overall reduction of NOS activity. ALF also decreased the content of the NOS cofactor, tetrahydro-L-biopterin (BH4), and evoked eNOS uncoupling (reduction of the eNOS dimer/monomer ratio). The addition of the NO precursor L-arginine in the absence of BH4 potentiated ROS accumulation, whereas nonspecific NOS inhibitor L-NAME or EDTA attenuated ROS increase. The ALF-induced decrease of eNOS content and its uncoupling concurred with, and was likely causally related to, both increased brain content of reactive oxidative species (ROS) and decreased cerebral cortical blood flow (CBF) in the same model.

Cerebrovascular reactivity and cerebral perfusion of rats with acute liver failure: role of L-glutamine and asymmetric dimethylarginine in L-arginine-induced response

Cerebral blood flow (CBF) is impaired in acute liver failure (ALF), however, the complexity of the underlying mechanisms has often led to inconclusive interpretations. Regulation of CBF depends at least partially on variations in the local brain L-arginine concentration and/or its metabolic rate. In ALF, other factors, like an increased concentration of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor and elevated level of L-glutamine, may contribute to CBF alteration. This study demonstrated strong differences in the reactivity of the middle cerebral arteries and their response to extravascular L-arginine application between vessels isolated from rats with thioacetamide (TAA)-induced ALF and control animals. Our results also showed the decrease in the cerebral perfusion in TAA rats measured by arterial spin labeling perfusion magnetic resonance. Subsequently, we aimed to investigate the importance of balance between the concentration of ADMA and L-arginine in the CBF regulation. In vivo, intraperitoneal L-arginine administration in TAA rats corrected: (i) decrease in cerebral perfusion, (ii) decrease in brain extracellular L-arginine/ADMA ratio and (iii) increase in brain L-glutamine concentration. Our study implicates that impaired vascular tone of cerebral arteries is most likely associated with exposure to high ADMA and L-glutamine levels resulting in limited availability of L-arginine and might be responsible for reduced cerebral perfusion observed in ALF.