Role of Mitochondrial Cytochrome P450 2E1 in Healthy and Diseased Liver

Cytochrome P450 2E1 (CYP2E1) is pivotal in hepatotoxicity induced by alcohol abuse and different xenobiotics. In this setting, CYP2E1 generates reactive metabolites inducing oxidative stress, mitochondrial dysfunction and cell death. In addition, this enzyme appears to play a role in the progression of obesity-related fatty liver to nonalcoholic steatohepatitis. Indeed, increased CYP2E1 activity in nonalcoholic fatty liver disease (NAFLD) is deemed to induce reactive oxygen species overproduction, which in turn triggers oxidative stress, necroinflammation and fibrosis. In 1997, Avadhani’s group reported for the first time the presence of CYP2E1 in rat liver mitochondria, and subsequent investigations by other groups confirmed that mitochondrial CYP2E1 (mtCYP2E1) could be found in different experimental models. In this review, we first recall the main features of CYP2E1 including its role in the biotransformation of endogenous and exogenous molecules, the regulation of its expression and activity and its involvement in different liver diseases. Then, we present the current knowledge on the physiological role of mtCYP2E1, its contribution to xenobiotic biotransformation as well as the mechanism and regulation of CYP2E1 targeting to mitochondria. Finally, we discuss experimental investigations suggesting that mtCYP2E1 could have a role in alcohol-associated liver disease, xenobiotic-induced hepatotoxicity and NAFLD.

Evaluation of Optimal Reference Genes for qRT-PCR Analysis in Hyphantria cunea (Drury)

The relative quantification of gene expression is mainly achieved through reverse transcription-quantitative PCR (qRT-PCR); however, its reliability and precision rely on proper data normalization using one or more optimal reference genes. Hyphantria cunea (Drury) has been an invasive pest of forest trees, ornamental plants, and fruit trees in China for many years. Currently, the molecular physiological role of reference genes in H. cunea is unclear, which hinders functional gene study. Therefore, eight common reference genes, RPS26, RPL13, UBI, AK, RPS15, EIF4A, β-actin, α-tub, were selected to evaluate levels of gene expression stability when subjected to varied experimental conditions, including developmental stage and gender, different tissues, larvae reared on different hosts and different larval density. The geNorm, BestKeeper, ΔCt method, and NormFinder statistical algorithms were used to normalize gene transcription data. Furthermore, the stability/suitability of these candidates was ranked overall by RefFinder. This study provides a comprehensive evaluation of reference genes in H. cunea and could help select reference genes for other Lepidoptera species.

Role of Yap1 in adult neural stem cell activation

Most adult hippocampal neural stem cells (NSCs) remain quiescent with only a minor portion undergoing active proliferation and neurogenesis. The molecular mechanisms that trigger eventually the transition from quiescence to activation are still poorly understood. Here, we found the activity of the transcriptional activator Yap1 to be enriched in active NSCs. Genetic deletion of Yap1 led to a significant reduction in the relative proportion of active NSCs supporting a physiological role of Yap1 in regulating the transition from quiescence to activation. Overexpression of wild type Yap1 in adult NSCs did not induce NSC activation suggesting tight upstream control mechanisms, but overexpression of a gain-of-function mutant (Yap1-5SA) elicited cell cycle entry in NSCs and hilar astrocytes. Consistent with a role of Yap1 in NSC activation, single cell RNA sequencing revealed the partial induction of an activated NSC gene expression program. Yet, Yap1-5SA expression also induced Taz and other key components of the Yap/Taz regulon previously identified in glioblastoma stem cell-like cells. Consequently, dysregulated Yap1 activity led to repression of hippocampal neurogenesis, promoting aberrant differentiation instead.

Modified Sawhorse Waveform for the Voltammetric Detection of Oxytocin

Carbon fiber microelectrodes (CFMEs) have been used to detect neurotransmitters and other biomolecules using fast-scan cyclic voltammetry (FSCV) for the past few decades. This technique measures neurotransmitters such as dopamine and, more recently, physiologically relevant neuropeptides. Oxytocin, a pleiotropic peptide hormone, is physiologically important for adaptation, development, reproduction, and social behavior. This neuropeptide functions as a stress-coping molecule, an anti-inflammatory agent, and serves as an antioxidant with protective effects especially during adversity or trauma. Here, we measure tyrosine using the Modified Sawhorse Waveform (MSW), enabling enhanced electrode sensitivity for the amino acid and oxytocin peptide. Applying the MSW, decreased surface fouling and enabled codetection with other monoamines. As oxytocin contains tyrosine, the MSW was also used to detect oxytocin. The sensitivity of oxytocin detection was found to be 3.99 ± 0.49 nA/µM, (n=5). Additionally, we demonstrate that applying the MSW on CFMEs allows for real time measurements of exogenously applied oxytocin on rat brain slices. These studies may serve as novel assays for oxytocin detection in a fast, sub-second timescale with possible implications for in vivo measurements and further understanding of the physiological role of oxytocin.

The circular RNA circGlis3 protects against islet β-cell dysfunction and apoptosis during obesity

The molecular link between obesity and β-cell decompensation that causes diabetes remains incompletely understood. Here we found that circGlis3, a circular RNA derived from Glis3, plays a critical role in islet β-cell compensation. circGlis3 was increased in islets of obese mouse models and moderately diabetic individuals with compensated β-cell function by Quaking (QKI)-mediated splicing. Overexpression of circGlis3 functions to restrain islet β-cell dysfunction and maintain β-cell mass in high-fat diet (HFD) fed mice and Leprdb/db mice. The cellular levels of circGlis3 modulate both insulin synthesis and secretion and lipotoxicity-induced apoptosis, resulting in profound changes in β-cell compensation. In an obesity model, circGlis3 promotes the synthesis and secretion of insulin by upregulating NeuroD1 and Creb1 through sponging miR-124-3p. In addition, we identified SCOTIN and fused in sarcoma (FUS) as interacting proteins using quantitative mass spectrometry. We demonstrated that the binding of SCOTIN to circGlis3 regulated the apoptosis of β-cell. And more, FUS binding to circGlis3 could decrease free circGlis3 in cytoplasm and block mechanism of circGlis3 via abnormal stable formation of stress granules (SGs) in hyperactive response to chronic stresses in obesity that is thought to contribute to the β-cell decompensation. These findings highlight a physiological role for circRNAs in compensation and indicate that modulation of circGlis3 expression may represent a potential strategy to protect against islet β-cell dysfunction and apoptosis during obesity.

Adipokines: inflammation and the pleiotropic role of white adipose tissue

I had been working on the endocrine and signalling role of white adipose tissue (WAT) since 1994 following the identification of the ob (Lep) gene(1), this after some 15 years investigating the physiological role of brown adipose tissue. The ob gene, a mutation in which it is responsible for the profound obesity of ob/ob (Lepob/Lepob) mice, is expressed primarily in white adipocytes and encodes the pleiotropic hormone leptin. The discovery of this adipocyte hormone had wide-ranging implications, including that white fat has multiple functions that far transcend the traditional picture of a simple lipid storage organ.

Disrupting GPCR Complexes with Smart Drug-like Peptides

G protein-coupled receptors (GPCRs) are a superfamily of proteins classically described as monomeric transmembrane (TM) receptors. However, increasing evidence indicates that many GPCRs form higher-order assemblies made up of monomers pertaining to identical (homo) or to various (hetero) receptors. The formation and structure of these oligomers, their physiological role and possible therapeutic applications raise a variety of issues that are currently being actively explored. In this context, synthetic peptides derived from TM domains stand out as powerful tools that can be predictably targeted to disrupt GPCR oligomers, especially at the interface level, eventually impairing their action. However, despite such potential, TM-derived, GPCR-disrupting peptides often suffer from inadequate pharmacokinetic properties, such as low bioavailability, a short half-life or rapid clearance, which put into question their therapeutic relevance and promise. In this review, we provide a comprehensive overview of GPCR complexes, with an emphasis on current studies using GPCR-disrupting peptides mimicking TM domains involved in multimerization, and we also highlight recent strategies used to achieve drug-like versions of such TM peptide candidates for therapeutic application.

Utility of vitamin D serum evaluation and supplementation in dogs and cats’ medical routine: a review

Vitamin D is traditionally known for its role in regulating calcium homeostasis and consequently maintaining bone integrity and health. However, more recently, it has been observed that it has a series of previously unknown non-canonical functions, such as maintenance of immunity and intestinal mucosa integrity. Furthermore, it has been shown to be associated with the progression or perpetuation of several diseases since its serum concentration is reduced during the course of the conditions. Therefore, we sought to investigate, through a literature review, the usefulness of serum vitamin D measurement in dogs and cats as a prognostic factor for different diseases, as well as the possible therapeutic effect of supplementing this vitamin in the correction of those illnesses. Vitamin D is in fact deficient in gastroenteric diseases, such as protein-losing enteropathy, infectious diseases, such as canine leishmaniasis, heart and kidney disease, among others. However, it is necessary to understand more properly about the physiological role of vitamin D in health, so that we can also understand it in disease. There are also too few data reports supporting supplementing this vitamin as main or adjuvant therapy in the treatment of any disease, but evidence points to the usefulness of vitamin D serum measurement as a prognostic predictor for dogs and cats.

Voltage-Dependent Anion Selective Channel 3: Unraveling Structural and Functional Features of the Least Known Porin Isoform

Voltage-dependent anion-selective channels (VDAC) are pore-forming proteins located in the outer mitochondrial membrane. Three isoforms are encoded by separate genes in mammals (VDAC1-3). These proteins play a crucial role in the cell, forming the primary interface between mitochondrial and cellular metabolisms. Research on the role of VDACs in the cell is a rapidly growing field, but the function of VDAC3 remains elusive. The high-sequence similarity between isoforms suggests a similar pore-forming structure. Electrophysiological analyzes revealed that VDAC3 works as a channel; however, its gating and regulation remain debated. A comparison between VDAC3 and VDAC1-2 underlines the presence of a higher number of cysteines in both isoforms 2 and 3. Recent mass spectrometry data demonstrated that the redox state of VDAC3 cysteines is evolutionarily conserved. Accordingly, these residues were always detected as totally reduced or partially oxidized, thus susceptible to disulfide exchange. The deletion of selected cysteines significantly influences the function of the channel. Some cysteine mutants of VDAC3 exhibited distinct kinetic behavior, conductance values and voltage dependence, suggesting that channel activity can be modulated by cysteine reduction/oxidation. These properties point to VDAC3 as a possible marker of redox signaling in the mitochondrial intermembrane space. Here, we summarize our current knowledge about VDAC3 predicted structure, physiological role and regulation, and possible future directions in this research field.