Case reports of latent HBV hepatitis in patients after neurosurgical treatment for hypothalamic and pituitary tumors.

BACKGROUND: Hepatitis B virus (HBV) infection is a major public health problem worldwide. More than 2 billion people have been exposed to HBV, and about 257 million individuals are chronic carriers of HBV. HBV reactivation has been increasingly reported in HBV carriers who have undergone immunosuppression or chemotherapy, resulting in mortality. Treatment of hypothalamic/pituitary tumors in HBV carriers requires extensive care to avoid HBV reactivation as steroid therapy is required after surgery for hypothalamic/pituitary tumors. CASE PRESENTATION: This retrospective review identified 5 patients, who were HBV carriers positive for hepatitis B surface antigen among 1352 patients with surgically treated hypothalamic/pituitary tumor in Kohnan Hospital between February 2007 and April 2017. Transsphenoidal surgery was performed with particular attention to prevent damage to the pituitary gland, with delicate manipulation to minimize postoperative steroid coverage. All patients received nucleot(s)ide analogue to control HBV-DNA levels before the surgery. As a result, all patients had a good clinical course. Blood examinations found a transient increase of liver enzymes and HBV-DNA levels in all patients, which started to decrease within 2 weeks after surgery. No specific treatment other than nucleot(s)ide analogues was needed to maintain liver function, and all patients returned to their previous activities including reinstatement. CONCLUSION: Initiation of nucleot(s)ide analogues administration prior to the surgery for hypothalamic/pituitary tumors can be an effective strategy for preventing reactivation in HBV carriers. Appropriate screening of the patient's HBV phase, optimal timing of nucleot(s)ide analogues -administration, and administration period of nucleot(s)ide analogues need to be established.

A neuron-specific enhancer targets expression of the gonadotropin-releasing hormone gene to hypothalamic neurosecretory neurons.

The molecular mechanisms specifying gene expression in individual neurons of the mammalian central nervous system have been difficult to study due to the cellular complexity of the brain and the absence of cultured model systems representing differentiated central nervous system neurons. We have developed clonal, differentiated, neuronal tumor cell lines of the hypothalamic GnRH-producing neurons by targeting tumorigenesis in transgenic mice. These cells (GT1 cells) provide a model system for molecular studies of GnRH gene regulation. Here we present the identification and characterization of a neuron-specific enhancer responsible for directing expression of the rat GnRH gene in GT1 hypothalamic neurons. This approximately 300 base pair (bp) upstream region (-1571 to -1863) confers enhancer activity to a short -173-bp GnRH promoter or to a heterologous promoter only in GT1 cells. The enhancer is bound by multiple GT1 nuclear proteins over its entire length. Deletion of more than 30 bp from either end dramatically reduces activity, and even large internal fragments carrying seven of the eight DNAse I-protected elements show decreased activity. Scanning replacement mutations demonstrate that several of the internal elements are required for activity of the enhancer. Thus, the GnRH gene is targeted to hypothalamic neurons by a complex multicomponent enhancer that relies on the interaction of multiple nuclear-protein binding enhancer elements.