Magyar, C. E. | Search bioRxiv

bioRxiv2020

1--4-phenylpiperazine Treatment After Brain Irradiation Preserves Cognitive Function in Mice

BackgroundNormal tissue toxicity to the CNS is an inevitable consequence of a successful radiotherapy of brain tumors or cancer metastases to the CNS. Cranial irradiation commonly leads to neurocognitive deficits that manifest months or years after treatment. Mechanistically, radiation-induced loss of neural stem/progenitor cells, neuro-inflammation and de-myelinization are contributing factors that lead to progressive cognitive decline. MethodsThe effects of Compound #5 on irradiated murine neurospheres, microglia cells and patients-derived gliomaspheres were assessed in sphere-formation assays, flow cytometry and IL-6 ELISAs, Activation of the Hedgehog pathway was studied by qRT-PCR. The in vivo effects of Compound #5 were analyzed using flow cytometry, sphere-formation assays, immune-histochemistry, behavioral testing and an intracranial mouse model of glioblastoma. ResultsWe report that 1-[(4-Nitrophenyl)sulfonyl]-4-phenylpiperazine (Compound #5) mitigates radiation-induced normal tissue toxicity in the brains of mice. Compound #5 treatment significantly increased the number of neural stem/progenitor cells after brain irradiation in female animals, inhibited radiation-induced microglia activation and expression of the pro-inflammatory cytokine interleukin-6. Behavioral testing revealed that treatment with Compound #5 after radiotherapy successfully mitigates radiation-induced decline in motor, sensory and memory function of the brain. In mouse models of glioblastoma, Compound #5 showed no toxicity and did not interfere with the growth-delaying effects of radiation. ConclusionsWe conclude that Compound #5 has the potential to mitigate cognitive decline in patients undergoing partial or whole brain irradiation without promoting tumor growth and that the use of this compound as a radiation mitigator of radiation late effects on the CNS warrants further investigation. Importance of the StudySuccessful radiotherapy of CNS malignancies inevitably lead to cognitive decline in cancer survivors and treatment options to mitigate this side effect are limited. We present evidence that a piperazine compound can prevent cognitive decline in mice after total brain irradiation without compromising the antitumor effect of radiation, suggesting that this compound could be used to mitigate radiation side effects in brain tumor patients undergoing radiotherapy.

neuroscience↗

bioRxiv2019

Genetic variants disrupt human RGS14 binding to NHERF1 and regulation of NPT2A-mediated phosphate transport

RGS14 is a multifunctional scaffolding protein that integrates G protein, MAPK, and Ca++/CaM signaling pathways. RGS14 contains an RGS domain, tandem Ras/Rap-binding domains, and a G protein regulatory motif. Human/primate RGS14 differ from rodent proteins by possessing a carboxy-terminal extension encoding a Type I PDZ ligand. RGS14 has been implicated in disordered phosphate metabolism. The human RGS14 gene is adjacent to SLC34A1 that encodes the NPT2A sodium-phosphate cotransporter. Hormone-regulated NPT2A requires the PDZ protein NHERF1 which contains two PDZ domains (PDZ1 and PDZ2). NHERF1 binds the PDZ ligand carboxy tail of NPT2A to regulate phosphate uptake, and this NPT2A:NHERF1 complex is inhibited by parathyroid hormone (PTH). Studies here define roles for RGS14 in NHERF1-dependent, PTH-sensitive phosphate transport. We found that RGS14 binds to NHERF1 via the PDZ2 domain. PTH inhibits NPT2A-mediated phosphate transport and RGS14 blocked this action. Several rare human mutations have been reported in the RGS14 PDZ ligand located at residues 563 (D563N, D563G) and 565 (A565S, A565V). D563N disrupted RGS14 binding to NHERF1 and did not interfere with PTH action, whereas D563G, A565S, and A565V bound NHERF1 and were functionally equivalent to wild-type RGS14. Computational analysis and molecular dynamics modeling of NHERF1 PDZ2 binding to the RGS14 C-terminal PDZ ligands refined the structural determinants of this interaction. Additional studies demonstrated that RGS14 is expressed in human kidney proximal and distal tubule cells. Together, our findings are consistent with the view that RGS14 contributes to PTH-sensitive phosphate transport in humans. RGS14 coding variants may cause disordered phosphate metabolism.

pharmacology and toxicology↗