Hypothalamo‑hypophysial system in rats with autotransplantation of the adrenal cortex

Identification of Reference Genes for Circadian Studies on Brain Microvessels and Choroid Plexus Samples Isolated from Rats

Delivery of putative compounds of therapeutic value to the brain is limited by brain barriers: the blood–brain barrier located in the endothelium of the brain microvessels (BrMV) and the blood–cerebrospinal fluid barrier located in the epithelium of the choroid plexus (ChP). Understanding their function and modulation by the circadian clock may enhance the efficacy of brain-targeting therapies. The aim of the present study was to evaluate the stability of 10 reference genes in the BrMV and ChP, isolated from male and female rats at six time points (ZT1, 5, 9, 13, 17, and 21). Gene evaluations were performed by qPCR, analyzed by RefFinder tool, and verified by analyzing the expression of the brain and muscle ARNT-like 1 (Bmal1) using the qPCR and digital PCR methods. We identified as the most stable genes for circadian studies tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein zeta (Ywhaz) and apolipoprotein E (Apoe) for BrMV, and beta actin (Actb) and hypoxanthine-guanine phosphoribosyltransferase (Hprt1) for ChP. After verification, ribosomal protein (Rps18) was also included as a sufficient reference gene. Additionally, the observed gender difference in the Bmal1 oscillations in both BrMV and ChP suggests that separate studies for each gender are recommended.

Effect of Lipopolysaccharide-Induced Inflammatory Challenge on β-Glucuronidase Activity and the Concentration of Quercetin and Its Metabolites in the Choroid Plexus, Blood Plasma and Cerebrospinal Fluid

Quercetin-3-glucuronide (Q3GA), the main phase II metabolite of quercetin (Q) in human plasma, is considered to be a more stable form of Q for transport with the bloodstream to tissues, where it can be potentially deconjugated by β-glucuronidase (β-Gluc) to Q aglycone, which easily enters the brain. This study evaluates the effect of lipopolysaccharide (LPS)-induced acute inflammation on β-Gluc gene expression in the choroid plexus (ChP) and its activity in blood plasma, ChP and cerebrospinal fluid (CSF), and the concentration of Q and its phase II metabolites in blood plasma and CSF. Studies were performed on saline- and LPS-treated adult ewes (n = 40) receiving Q3GA intravenously (n = 16) and on primary rat ChP epithelial cells and human ChP epithelial papilloma cells. We observed that acute inflammation stimulated β-Gluc activity in the ChP and blood plasma, but not in ChP epithelial cells and CSF, and did not affect Q and its phase II metabolite concentrations in plasma and CSF, except Q3GA, for which the plasma concentration was higher 30 min after administration (p < 0.05) in LPS- compared to saline-treated ewes. The lack of Q3GA deconjugation in the ChP observed under physiological and acute inflammatory conditions, however, does not exclude its possible role in the course of neurodegenerative diseases.

GATA4/6 regulate DHH transcription in rat adrenocortical autografts

Adrenal cortex autotransplantation with ACTH stimulation may be an alternative therapy for patients with bilateral adrenalectomy to avoid adrenal crisis, but its underlying mechanism has not been elucidated. Previously, we detected Dhh upregulation in rat adrenocortical autografts after transplantation. Here, we investigated potential regulators such as Gata4, Gata6, Sry and Sox9 which affect Dhh transcription in adrenocortical autografts with or without ACTH stimulation. In ACTH-stimulated autografts, Gata4 and Gata6 were downregulated compared to control autografts. This response was linked to rDhh repression. A reporter assay using the upstream region of rDhh and a GATA binding motif revealed that rDhh promoters were significantly upregulated by co-transfection with Gata4 or Gata6 or both. Sry and Sox9 expression in autografts with or without ACTH stimulation were verified by PCR and RNAscope analyses. The ovarian differentiation factors Foxl2 and Rspo1 were also upregulated in the autografts. Gata4 and Gata6 were found to be significant factors in the regulation of rDhh expression and could be associated with adrenocortical autograft maintenance. Gonadal primordia with bipotential testicular and ovarian functions may also be present in these autografts.

Involvement of PLAGL1/ZAC1 in hypocretin/orexin transcription

The hypocretin/orexin neuropeptide system coordinates the regulation of various physiological processes. Our previous study reported that a reduction in the expression of pleomorphic adenoma gene-like 1 (Plagl1), which encodes a C2H2 zinc-finger transcription factor, occurs in hypocretin neuron-ablated transgenic mice, suggesting that PLAGL1 is co-expressed in hypocretin neurons and regulates hypocretin transcription. The present study examined whether canonical prepro-hypocretin transcription is functionally modulated by PLAGL1. Double immunostaining indicated that the majority of hypocretin neurons were positive for PLAGL1 immunore-activity in the nucleus. Notably, PLAGL1 immunoreactivity in hypocretin neurons was altered in response to several conditions affecting hypocretin function. An uneven localization of PLAGL1 was detected in the nuclei of hypocretin neurons following sleep deprivation. Chromatin immunoprecipitation revealed that endogenous PLAGL1 may bind to a putative PLAGL1-binding site in the proximal region of the hypocretin gene, in the murine hypothalamus. In addition, electroporation of the PLAGL1 expression vector into the fetal hypothalamus promoted hypothalamic hypocretin transcription. These results suggested that PLAGL1 may regulate hypothalamic hypocretin transcription.

Involvement of DHH and GLI1 in adrenocortical autograft regeneration in rats

Bilateral adrenalectomy forces the patient to undergo glucocorticoid replacement therapy and bear a lifetime risk of adrenal crisis. Adrenal autotransplantation is considered useful to avoid adrenal crisis and glucocorticoid replacement therapy. However, the basic process of regeneration in adrenal autografts is poorly understood. Here, we investigated the essential regeneration factors in rat adrenocortical autografts, with a focus on the factors involved in adrenal development and steroidogenesis, such as Hh signalling. A remarkable renewal in cell proliferation and increase in Cyp11b1, which encodes 11-beta-hydroxylase, occurred in adrenocortical autografts from 2-3 weeks after autotransplantation. Serum corticosterone and adrenocorticotropic hormone levels were almost recovered to sham level at 4 weeks after autotransplantation. The adrenocortical autografts showed increased Dhh expression at 3 weeks after autotransplantation, but not Shh, which is the only Hh family member to have been reported to be expressed in the adrenal gland. Increased Gli1 expression was also found in the regenerated capsule at 3 weeks after autotransplantation. Dhh and Gli1 might function in concert to regenerate adrenocortical autografts. This is the first report to clearly show Dhh expression and its elevation in the adrenal gland.