SREBP1 deficiency diminishes glutamate-mediated HT22 cell damage and hippocampal neuronal pyroptosis induced by status epilepticus.

Status epilepticus (SE) is a life-threatening disorder that can result in death or severe brain damage, and there is a substantial body of evidence suggesting a strong association between pyroptosis and SE. Sterol regulatory element binding protein 1 (SREBP1) is a significant transcription factor participating in both lipid homeostasis and glucose metabolism. However, the function of SREBP1 in pyroptosis during SE remains unknown. In this study, we established a SE rat model by intraperitoneal injection of lithium chloride and pilocarpine in vivo. Additionally, we treated HT22 hippocampal cells with glutamate to create neuronal injury models in vitro. Our results demonstrated a significant induction of SREBP1, inflammasomes, and pyroptosis in the hippocampus of SE rats and glutamate-treated HT22 cells. Moreover, we found that SREBP1 is regulated by the mTOR signaling pathway, and inhibiting mTOR signaling contributed to the amelioration of SE-induced hippocampal neuron pyroptosis, accompanied by a reduction in SREBP1 expression. Furthermore, we conducted siRNA-mediated knockdown of SREBP1 in HT22 cells and observed a significant reversal of glutamate-induced cell death, activation of inflammasomes, and pyroptosis. Importantly, our confocal immunofluorescence analysis revealed the co-localization of SREBP1 and NLRP1. In conclusion, our findings suggest that deficiency of SREBP1 attenuates glutamate-induced HT22 cell injury and hippocampal neuronal pyroptosis in rats following SE. Targeting SREBP1 may hold promise as a therapeutic strategy for SE.

Identification of a new function of metallothionein-like gene OsMT1e for cadmium detoxification and potential phytoremediation.

Cadmium (Cd) is a biologically non-essential and toxic heavy metal leaking to the environment via natural emission or anthropogenic activities, thereby contaminating crops and threatening human health. Metallothioneins (MTs) are a group of metal-binding proteins playing critical roles in metal allocation and homeostasis. In this study, we identified a novel function of OsMT1e from rice plants. OsMT1e was dominantly expressed in roots at all developmental stages and, to less extent, expressed in leaves at vegetative and seed filling stages. OsMT1e was mainly targeted to the nucleus and substantially induced by Cd exposure. Expression of OsMT1e in a yeast Cd-sensitive strain ycf1 conferred cellular tolerance to Cd, even though the ycf1 + OsMT1e cells accumulated more Cd than the control cells (ycf1 + pYES2). Both transgenic rice overexpressing (OX) and repressing OsMT1e by RNA interference (RNAi) were developed. Phenotypic analysis revealed that OsMT1e overexpression enhanced the rice growth concerning the increased shoot or root elongation, dry weight and chlorophyll contents, whereas the RNAi lines displayed a sensitive growth phenotype compared to wild-type. Assessment with 0.5, 2 and 10 µM Cd for two weeks revealed that the RNAi lines accumulated less Cd, while the OX lines had an increased Cd accumulation in root and shoot tissues. The contrasting Cd accumulation phenotypes between the OX and RNAi lines were further confirmed by a long-term study with 0.5 µM Cd for one month. Overall, the study unveiled a new function of OsMT1e in rice, which can be potentially used for engineering genotypes for phytoremediation or minimizing Cd in rice crops.

Identification of novel rice (Oryza sativa) HPP and HIPP genes tolerant to heavy metal toxicity.

HPP (heavy metal associated plant protein) and HIPP (heavy metal associated isoprenylated plant protein) are a group of metal-binding metallochaperones playing crucial roles in metal homeostasis and detoxification. Up to now, only few of them have been functionally identified in plants. Here, we identified 54 HPP and HIPP genes in rice genome. Analysis of the transcriptome datasets of the rice genome exposed to cadmium (Cd) revealed 17 HPP/HIPP genes differentially expressed, with 11 being upregulated (>2 fold change, p < 0.05). Comprehensive analysis of transcripts by qRT-PCR showed that both types of genes displayed diverse expression pattern in rice under excess manganese (Mn), copper (Cu) and Cd stress. Multiple genomic analyses of HPPs/HIPPs including phylogenesis, conserved domains and motifs, genomic arrangement and genomic and tandem duplication were performed. To identify the role of the genes, OsHIPP16, OsHIPP34 and OsHIPP60 were randomly selected to express in yeast (Saccharomyces cerevisiae) mutants pmrl, cup2, ycf1 and zrc1, exhibiting sensitivity to Mn, Cu, Cd and Zn toxicity, respectively. Complementation test showed that the transformed cells accumulated more metals in the cells, but their growth status was improved. To confirm the functional role, two mutant oshipp42 lines defective in OsHIPP42 expression were identified under metal stress. Under normal condition, no difference of growth between the oshipp42 mutant and wild-type plants was observed. Upon excess Cu, Zn, Cd and Mn, the oshipp42 lines grew weaker than the wild-type. Our work provided a novel source of heavy metal-binding genes in rice that can be potentially used to develop engineered plants for phytoremediation in heavy metal-contaminated soils.