Selective lysine-specific demethylase 1 inhibitor, NCL1, could cause testicular toxicity via the regulation of apoptosis

Background

Recent studies have shown that epigenetic alterations, such as those involving lysine‐specific demethylase 1 (LSD1), lead to oncogenic activation and highlight such alterations as therapeutic targets. However, studies evaluating the effect of LSD1 inhibitors on male fertility are lacking.

Objectives

We analyzed the potential toxicity of a new selective LSD1 inhibitor, N‐[(1S)‐3‐[3‐(trans‐2‐aminocyclopropyl)phenoxy]‐1‐(benzylcarbamoyl)propyl] benzamide (NCL1), in testes.

Materials and methods

Human testicular samples were immunohistochemically analyzed. Six‐week‐old male C57BL/6J mice were injected intraperitoneally with dimethyl sulfoxide vehicle (n = 15), or 1.0 (n = 15) or 3.0 (n = 15) mg/kg NCL1 biweekly. After five weeks, toxicity and gene expression were analyzed in testicular samples by ingenuity pathway analysis (IPA) using RNA sequence data and quantitative reverse transcriptase (qRT)–PCR; hormonal damage was analyzed in blood samples. NCL1 treated GC‐1, TM3, and TM4 cell lines were analyzed by cell viability, chromatin immunoprecipitation, flow cytometry, and Western blot assays.

Results

LSD1 was mainly expressed in human Sertoli and germ cells, with LSD1 levels significantly decreased in a progressive meiosis‐dependent manner; germ cells showed similar expression patterns in normal spermatogenesis and early/late maturation arrest. Histological examination revealed significantly increased levels of abnormal seminiferous tubules in 3.0 mg/kg NCL1–treated mice compared to control, with increased cellular detachment, sloughing, vacuolization, eosinophilic changes, and TUNEL‐positive cells. IPA and qRT–PCR revealed NCL1 treatment down‐regulated LSD1 activity. NCL1 also reduced total serum testosterone levels. Western blots of mouse testicular samples revealed NCL1 induced a marked elevation in cleaved caspases 3, 7, and 8, and connexin 43 proteins. NCL1 treatment significantly reduced GC‐1, but not TM3 and TM4, cell viability in a dose‐dependent manner. In flow cytometry analysis, NCL1 induced apoptosis in GC‐1 cells.

Conclusions

High‐dose NCL1 treatment targeting LSD1 caused dysfunctional spermatogenesis and induced caspase‐dependent apoptosis. This suggests the LSD1 inhibitor may cause testicular toxicity via the regulation of apoptosis.

Characteristics of PPT1 and TPP1 enzymes in neuronal ceroid lipofuscinosis (NCL) 1 and 2 by dried blood spots (DBS) and leukocytes and their application to newborn screening

We first characterized PPT1 and TPP1 enzymes in dried blood spots (DBS), plasma/serum, and leukocytes/lymphocytes using neuronal ceroid lipofuscinosis (NCL) 1 and 2 patients and control subjects. PPT1 enzyme had only one acid form in control DBS, plasma/serum, and leukocytes/lymphocytes and showed deficient activities in these samples from NCL 1 patients. Conversely, TPP1 enzymes in control DBS and leukocytes/lymphocytes consisted of two forms, an acidic form and a neutral form, whereas serum TPP1 enzyme had only a neutral form. In control subjects, the optimal pH of PPT1 enzyme in DBS, plasma/serum, and leukocytes/lymphocytes was 4.5 to 5.0 in the acidic form, whereas TPP1 enzyme in control DBS and leukocytes/lymphocytes was pH 4.5 and 6.5, respectively. In NCL 1 and 2, both PPT1 and TPP1 enzyme activities in DBS, plasma, and leukocytes/lymphocytes were markedly reduced in acidic pH, whereas heterozygotes of NCL 1 and 2 in the acidic form showed intermediate activities between patients and control subjects. In neutral conditions, pH 6.0, the PPT1 enzyme activities in NCL 1 patients showed rather higher residual activities and intermediate activities in heterozygotes in NCL 1, which was probably caused by mutated proteins in three cases with NCL 1 patients. TPP1 enzyme activities at neutral pH 6.5 to 7.0 in DBS and leukocytes/lymphocytes showed higher enzyme activities in NCL 2 patients and heterozygotes. The reason for the increases of neutral TPP1 enzyme activities at pH 6.5 to 7.0 in NCL 2 DBS and leukocytes/lymphocytes, is obscure, but possibly caused by secondary activation of neutral TPP1 enzyme due to the absence of the acidic form. Interestingly, TPP1 activity in serum only consisted of a neutral form, no acidic form, and was not deficient in any NCL 2 patient. Therefore, we can diagnose NCL 1 patients by plasma/serum enzyme assay of PPT1, but not diagnose NCL 2 by serum TPP1 enzyme assay. A pilot study of newborn screening of NCL 1 and 2 has been established by more than 1000 newborn DBS assays. Using this assay system, we will be able to perform newborn screening of NCL 1 and 2 by DBS.