Endogenous Function Research Articles

Anxiety enhances pain in a model of osteoarthritis and is associated with altered endogenous opioid function and reduced opioid analgesia.

Negative affect, including anxiety and depression, is prevalent in chronic pain states such as osteoarthritis (OA) and associated with greater use of opioid analgesics, potentially contributing to present and future opioid crises. We tested the hypothesis that the interaction between anxiety, chronic pain, and opioid use results from altered endogenous opioid function. A genetic model of negative affect, the Wistar-Kyoto (WKY) rat, was combined with intra-articular injection of monosodium iodoacetate (MIA; 1 mg) to mimic clinical presentation. Effects of systemic morphine (0.5-3.5 mg·kg-1) on pain behaviour and spinal nociceptive neuronal activity were compared in WKY and normo-anxiety Wistar rats 3 weeks after MIA injection. Endogenous opioid function was probed by the blockade of opioid receptors (0.1-1 mg·kg-1 systemic naloxone), quantification of plasma β-endorphin, and expression and phosphorylation of spinal mu-opioid receptor (MOR). Monosodium iodoacetate-treated WKY rats had enhanced OA-like pain, blunted morphine-induced analgesia, and greater mechanical hypersensitivity following systemic naloxone, compared with Wistar rats, and elevated plasma β-endorphin levels compared with saline-treated WKY controls. Increased MOR phosphorylation at the master site (serine residue 375) in the spinal cord dorsal horn of WKY rats with OA-like pain (P = 0.0312) indicated greater MOR desensitization. Reduced clinical analgesic efficacy of morphine was recapitulated in a model of high anxiety and OA-like pain, in which endogenous opioid tone was altered, and MOR function attenuated, in the absence of previous exogenous opioid ligand exposure. These findings shed new light on the mechanisms underlying the increased opioid analgesic use in high anxiety patients with chronic pain.

Physical activity behavior in the first month after mild traumatic brain injury is associated with physiological and psychological risk factors for chronic pain.

The purpose of this study was to determine whether self-reported physical activity (PA) in the first month after mild traumatic brain injury (mTBI) predicts endogenous pain modulatory function and pain catastrophizing at 1 to 2 weeks and 1 month after injury in patients with mTBI. Patients with mild traumatic brain injury completed study sessions at 1 to 2 weeks and 1 month after injury. Assessments included a headache survey, Pain Catastrophizing Scale, International Physical Activity Questionnaire-Short Form, and several quantitative sensory tests to measure endogenous pain modulatory function including conditioned pain modulation (CPM), temporal summation, and pressure pain thresholds of the head. Hierarchical linear regressions determined the relationship between the PA variables (predictors) and pain catastrophizing and pain modulation variables (dependent variables) cross-sectionally and longitudinally, while controlling for potential covariates. In separate hierarchical regression models, moderate PA, walking, and total PA at 1 to 2 weeks after injury predicted pain inhibition on the CPM test at 1 month, after controlling for significant covariates. In addition, a separate regression revealed that minutes sitting at 1 month predicted CPM at 1 month. Regarding predicting pain catastrophizing, the regression results showed that sitting at 1 to 2 weeks after injury significantly predicted pain catastrophizing at 1 month after injury. Greater self-reported PA, especially moderate PA, 1 to 2 weeks after injury longitudinally predicted greater pain inhibitory capacity on the CPM test at 1 month after injury in patients with mTBI. In addition, greater sedentary behavior was associated with worse pain inhibition on the CPM test and greater pain catastrophizing at 1 month after injury.

HEAT SHOCK PROTEIN HSP70: PREREQUISITES FOR USE AS A MEDICINAL PRODUCT

Heat shock protein Hsp70 is one of the main cytoprotection components under the action of various external stimuli. The analysis of the literature data shows that nowadays, the researches’ overwhelming evidence has proven the role of Hsp70 as a biological target for the drug development; however, the ideas about its use as a drug are often multidirectional.The aim of the article is to analyze and generalize the literature data on the features of the physiological functions of heat shock protein Hsp 70, and indicate the possibilities of its use for the pharmacological correction of various pathological conditions.Materials and methods. In the process of selecting material for writing this review article, such databases as Google Patents, Science Research Portal, Google Scholar, ScienceDirect, CiteSeer, Publications, ResearchIndex, Ingenta, PubMed, KEGG, etc. were used The following words and word combinations were selected as markers for identifying the literature: Hsp70, Hsp70 stroke, Hsp70 neuroprotection, Hsp70 cytoprotection, recombinant drugs.Results. In this review, the pharmacology of one of the key members of this family, Hsp70, was focused on. The literary analysis confirms that this molecule is an endogenous regulator of many physiological processes and demonstrates tissue protective effects in modeling ischemic, neurodegenerative and inflammatory processes. The use of recombinant exogenous Hsp70 mimics the endogenous function of the protein, indicating the absence of a number of typical limitations characteristic of pharmacotherapy with high molecular weight compounds, such as immunogenicity, a rapid degradation by proteases, or a low penetration of histohematogenous barriers.Conclusion. Thus, Hsp70 may become a promising agent for clinical trials as a drug for the treatment of patients with neurological, immunological, and cardiovascular profiles.

UPLC-TOF-MS Method for Simultaneous Quantification of Steroid Hormones in Tissue Homogenates of Zebrafish with Solid-Phase Extraction.

The quantification of steroid hormones of individual zebrafish (Danio rerio) provides perspective to understand endogenous hormone function. A UPLC–TOF–MS method was developed to provide a reproducible, sensitive, and efficient assay to determine the concentration of steroid hormones, including cortisol, testosterone, androstenedione, 11-deoxycortisol, 11-deoxycorticosterone, and 17-hydroxyprogesterone in whole-body homogenates of each zebrafish. Solid-phase extraction was used to sample matrix clean-up and acquired a recovery from 89.7% to 107.9%. The analytes were separated on an Aquity BEH C18 column using gradient elution. Mass spectrometric analysis was performed by single reaction monitoring (SRM) using positive electrospray ionization mode. The total running time was 6 min, which was greatly shortened compared with a previously reported method. The developed method exhibited excellent linearity for all the analytes, with regression coefficients higher than 0.99. The limit of detection varied between 0.1 and 0.5 ng/L and the limit of quantification was 0.5–1.7 ng/L for all analytes. The precision of the method was assessed on replicate measurements and was found to be in the ranges of 1.9 % to 6.6% and 4.3% to 8.6%, for intra- and inter-day analysis, respectively. This method was validated according to FDA guidance and applied to determine steroid hormone levels in the tissue homogenate of zebrafish acutely treated with caffeine and ethanol.

A functional genetic toolbox for human tissue-derived organoids.

Human organoid systems recapitulate key features of organs offering platforms for modelling developmental biology and disease. Tissue-derived organoids have been widely used to study the impact of extrinsic niche factors on stem cells. However, they are rarely used to study endogenous gene function due to the lack of efficient gene manipulation tools. Previously, we established a human foetal lung organoid system (Nikolić et al., 2017). Here, using this organoid system as an example, we have systematically developed and optimised a complete genetic toolbox for use in tissue-derived organoids. This includes 'Organoid Easytag', our efficient workflow for targeting all types of gene loci through CRISPR-mediated homologous recombination followed by flow cytometry for enriching correctly targeted cells. Our toolbox also incorporates conditional gene knockdown or overexpression using tightly inducible CRISPR interference and CRISPR activation which is the first efficient application of these techniques to tissue-derived organoids. These tools will facilitate gene perturbation studies in tissue-derived organoids facilitating human disease modelling and providing a functional counterpart to many ongoing descriptive studies, such as the Human Cell Atlas Project.

Androgen receptor splice variant 7 functions independently of the full length receptor in prostate cancer cells.

One mechanism for reactivation of androgen receptor (AR) activity after androgen deprivation therapy in castration-resistant prostate cancer (CRPC) is expression of splice variants such as ARv7 that delete the ligand binding domain and have constitutive activity. Exogenous overexpressed ARv7 can function as a homodimer or heterodimer with full length AR (ARfl), which is highly expressed with ARv7 in CRPC. However, the extent to which endogenous ARv7 function is dependent on heterodimerization with ARfl remains to be determined. We used double-crosslinking to stabilize AR complexes on chromatin in a CRPC cell line expressing endogenous ARfl and ARv7 (LN95cells), and established that only trace levels of ARfl were associated with ARv7 on chromatin. Consistent with this result, depletion of ARfl with an AR degrader targeting the AR ligand binding domain did not decrease ARv7 binding to chromatin or its association with HOXB13, but did decrease overall AR transcriptional activity. Comparable results were obtained in CWR22RV1 cells, another CRPC cell line expressing ARfl and ARv7. These results indicate that ARv7 function in CRPC is not dependent on ARfl, and that both contribute independently to overall AR activity.

Beta cell function as an assessment tool for cardiovascular risk in patients with metabolic syndrome

Background/Aim: Epicardial fat tissue (EFT) is considered a cardiovascular risk factor independent from visceral adiposity, obesity, hypertension, and diabetes. Fasting serum C-peptide is a known marker of endogenous insulin secretion and beta cell function. Our aim was to evaluate C- peptide levels in patients with metabolic syndrome (MetS) in relation to the EFT thickness. Methods: Forty-five subjects with MetS without a history of coronary artery disease and 25 healthy volunteers were enrolled this prospective case-control study. We examined the laboratory values, including C peptide, insulin, and HOMA-IR after 8 hours of fasting. EFT thickness was measured by two-dimensional transthoracic echocardiography. Results: The serum C peptide levels were significantly higher in patients with metabolic syndrome compared to the healthy controls [3.41(1.98) ng/ml vs 2.07 (1.39), P

Knock-in tagging in zebrafish facilitated by insertion into non-coding regions.

Zebrafish provide an excellent model for in vivo cell biology studies because of their amenability to live imaging. Protein visualization in zebrafish has traditionally relied on overexpression of fluorescently tagged proteins from heterologous promoters, making it difficult to recapitulate endogenous expression patterns and protein function. One way to circumvent this problem is to tag the proteins by modifying their endogenous genomic loci. Such an approach is not widely available to zebrafish researchers because of inefficient homologous recombination and the error-prone nature of targeted integration in zebrafish. Here, we report a simple approach for tagging proteins in zebrafish on their N or C termini with fluorescent proteins by inserting PCR-generated donor amplicons into non-coding regions of the corresponding genes. Using this approach, we generated endogenously tagged alleles for several genes that are crucial for epithelial biology and organ development, including the tight junction components ZO-1 and Cldn15la, the trafficking effector Rab11a, the apical polarity protein aPKC and the ECM receptor Integrin β1b. Our approach facilitates the generation of knock-in lines in zebrafish, opening the way for accurate quantitative imaging studies.

HPTE-Induced Embryonic Thymocyte Death and Alteration of Differentiation Is Not Rescued by ERα or GPER Inhibition but Is Exacerbated by Concurrent TCR Signaling.

Organochlorine pesticides, such as DDT, methoxychlor, and their metabolites, have been characterized as endocrine disrupting chemicals (EDCs); suggesting that their modes of action involve interaction with or abrogation of endogenous endocrine function. This study examined whether embryonic thymocyte death and alteration of differentiation induced by the primary metabolite of methoxychlor, HPTE, rely upon estrogen receptor binding and concurrent T cell receptor signaling. Estrogen receptor inhibition of ERα or GPER did not rescue embryonic thymocyte death induced by HPTE or the model estrogen diethylstilbestrol (DES). Moreover, adverse effects induced by HPTE or DES were worsened by concurrent TCR and CD2 differentiation signaling, compared with EDC exposure post-signaling. Together, these data suggest that HPTE- and DES-induced adverse effects on embryonic thymocytes do not rely solely on ER alpha or GPER but may require both. These results also provide evidence of a potential collaborative signaling mechanism between TCR and estrogen receptors to mediate adverse effects on embryonic thymocytes, as well as highlight a window of sensitivity that modulates EDC exposure severity.

The relationship between endogenous secretory RAGE and cardiac autonomic function in prediabetes.

The putative protective role of esRAGE for cardiac autonomic function (CAF) remains unclear. To address this question, the present study has assessed the relationship of serum AGEs, sRAGE and esRAGE, and tissue AGEs with CAF in a high-risk population without diabetes. This study enrolled 48 subjects of mean age 52.7±11.2years and mean BMI 28.4±6.3kg/m2 , divided into two groups according to glucose tolerance: 16 with normal glucose tolerance (NGT) and 24 with prediabetes. A standard oral glucose tolerance test (OGTT) was performed. The glucose tolerance was defined according to 2006 WHO criteria. Fasting, 120-minutes glucose, lipids, creatinine, and HbA1c were measured. eGFR was calculated (CKD-EPI). Fasting, 120-minutes insulin (ECLIA method), advanced glycation end products (AGEs), plasma-soluble receptor for AGE (sRAGE), and endogenous secreted isoform of the receptor for AGE (esRAGE), (ELISA method) were assessed. HOMA-IR was calculated. Tissue AGEs were assessed by skin autofluorescence (AGE-Reader, DiagnOpticsTM). CAF was evaluated with ANX 3.0 autonomic nervous-monitoring system (ANSAR), applying deep breathing, Valsalva, and standing. There was a significant decline in CAF in prediabetes in comparison with NGT. Serum and tissue AGEs, sRAGE, and esRAGE levels were similar between groups. On the matrix analysis, both sympathetic and parasympathetic activities at baseline and after standing and sympathetic tone during Valsalva were positively related to esRAGE in prediabetes. Multivariate regression analysis showed that esRAGE is an independent contributor to sympathetic, parasympathetic, and total autonomic tone in prediabetes accounting for about 28%, 34%, and 35% of their variances, respectively. Our results have demonstrated that CAF is decreased in prediabetes. esRAGE, but not sRAGE, is reciprocally related to CAF, probably opposing the negative effects of glycation.

Discrete cis-acting element regulates developmentally timed gene-lamina relocation and neural progenitor competence invivo.

SUMMARYThe nuclear lamina is typically associated with transcriptional silencing, and peripheral relocation of genes highly correlates with repression. However, the DNA sequences and proteins regulating gene-lamina interactions are largely unknown. Exploiting the developmentally timed hunchback gene movement to the lamina in Drosophila neuroblasts, we identified a 250 bp intronic element (IE) both necessary and sufficient for relocation. The IE can target a reporter transgene to the lamina and silence it. Endogenously, however, hunchback is already repressed prior to relocation. Instead, IE-mediated relocation confers a heritably silenced gene state refractory to activation in descendent neurons, which terminates neuroblast competence to specify early-born identity. Surprisingly, we found that the Polycomb group chromatin factors bind the IE and are required for lamina relocation, revealing a nuclear architectural role distinct from their well-known function in transcriptional repression. Together, our results uncover in vivo mechanisms underlying neuroblast competence and lamina association in heritable gene silencing.

UQCRC1 engages cytochrome c for neuronal apoptotic cell death.

Human ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) is an evolutionarily conserved core subunit of mitochondrial respiratory chain complex III. We recently identified the disease-associated variants of UQCRC1 from patients with familial parkinsonism, but its function remains unclear. Here we investigate the endogenous function of UQCRC1 in the human neuronal cell line and the Drosophila nervous system. Flies with neuronal knockdown of uqcrc1 exhibit age-dependent parkinsonism-resembling defects, including dopaminergic neuron reduction and locomotor decline, and are ameliorated by UQCRC1 expression. Lethality of uqcrc1-KO is also rescued by neuronally expressing UQCRC1, but not the disease-causing variant, providing a platform to discern the pathogenicity of this mutation. Furthermore, UQCRC1 associates with the apoptosis trigger cytochrome c (cyt-c), and uqcrc1 deficiency increases cyt-c in the cytoplasmic fraction and activates the caspase cascade. Depleting cyt-c or expression of the anti-apoptotic p35 ameliorates uqcrc1-mediated neurodegeneration. Our findings identify a role for UQCRC1 in regulating cyt-c-induced apoptosis.

Fc Receptor Variants and Disease: A Crucial Factor to Consider in the Antibody Therapeutics in Clinic.

The fragment crystallizable (Fc) domain of antibodies is responsible for their protective function and long-lasting serum half-life via Fc-mediated effector function, transcytosis, and recycling through its interaction with Fc receptors (FcRs) expressed on various immune leukocytes, epithelial, and endothelial cells. Therefore, the Fc–FcRs interaction is a control point of both endogenous and therapeutic antibody function. There are a number of reported genetic variants of FcRs, which include polymorphisms in (i) extracellular domain of FcRs, which change their affinities to Fc domain of antibodies; (ii) both cytoplasmic and intracellular domain, which alters the extent of signal transduction; and (iii) the promoter region of the FcRs gene, which affects the expression level of FcRs, thus being associated with the pathogenesis of disease indications. In this review, we firstly describe the correlation between the genetic variants of FcRs and immunological disorders by individual differences in the extent of FcRs-mediated regulations. Secondly, we discuss the influence of the genetic variants of FcRs on the susceptibility to infectious diseases or cancer in the perspective of FcRs-induced effector functions. Overall, we concluded that the genetic variants of FcRs are one of the key elements in the design of antibody therapeutics due to their variety of clinical outcomes among individuals.

Choice of foreign exchange intervention and inflation targeting commitment

We derive a model in which the decision to intervene in the foreign exchange market becomes an endogenous function of the variance of exogenous shocks and parameters of the model. The central bank evaluates a social welfare loss function under four scenarios including a foreign exchange intervention or non-intervention regimes under both discretionary and commitment type arrangements for administering monetary policy. The model shows that under either a discretionary regime, or a regime characterized as one which commits, the decision to intervene or not to intervene in the forex market depends on an endogenous equation of shallow parameters. Under either intervention or non-intervention, commitment to a policy rule dominates discretion.

The fushi tarazu zebra element is not required for Drosophila viability or fertility.

Expression of genes in precisely controlled spatiotemporal patterns is essential for embryonic development. Much of our understanding of mechanisms regulating gene expression comes from the study of cis-regulatory elements (CREs) that direct expression of reporter genes in transgenic organisms. This reporter-transgene approach identifies genomic regions sufficient to drive expression but fails to provide information about quantitative and qualitative contributions to endogenous expression, although such conclusions are often inferred. Here we evaluated the endogenous function of a classic Drosophila CRE, the fushi tarazu (ftz) zebra element. ftz is a pair-rule segmentation gene expressed in seven stripes during embryogenesis, necessary for formation of alternate body segments. Reporter transgenes identified the promoter-proximal zebra element as a major driver of the seven ftz stripes. We generated a precise genomic deletion of the zebra element (ftzΔZ) to assess its role in the context of native chromatin and neighboring CREs, expecting large decreases in ftz seven-stripe expression. However, significant reduction in expression was found for only one stripe, ftz stripe 4, expressed at ∼25% of wild type levels in ftzΔZ homozygotes. Defects in corresponding regions of ftzΔZ mutants suggest this level of expression borders the threshold required to promote morphological segmentation. Further, we established true-breeding lines of homozygous ftzΔZ flies, demonstrating that the body segments missing in the mutants are not required for viability or fertility. These results highlight the different types of conclusions drawn from different experimental designs and emphasize the importance of examining transcriptional regulatory mechanisms in the context of the native genomic environment.

False-Negative Results in Taqman One-Step RT-PCR Test: Evaluation of Endogenous Internal Control Function Used in SARS-CoV-2 Detection Tests

Background: Taqman one-step real-time PCR (RT-PCR) has special importance due to its high sensitivity and specificity in the diagnosis of infectious diseases such as viral infections. In the recent pandemic of SARS-CoV-2, diagnostic kits based on this method are commonly used for molecular detection. One of the main systematic errors that misinterpret the results is using inaccurate internal control in RT-PCR diagnostic kits. Designing primers and probes that span exon-exon junction will avoid genomic DNA amplification and lead to obtaining high specific results. Objectives: This study aimed to evaluate the endogenous internal control of primers and probe for RNase P RNA to reduce false-negative results in respiratory samples. Methods: In this study, 30 samples of patients who were negative for SARS-CoV-2, influenza A, and influenza B were re-evaluated for SARS-CoV-2 using newly designed primers and probes for RNase P RNA (ultra-specific primers and probe). We also performed bioinformatics analysis on CDC-approved primers and probes of RNase P endogenous internal control. Results: In this analysis, we specified the location of these newly designed primers and probe on target mRNA and genomic DNA. Then, the Taqman one-step RT-PCR method was performed using both CDC-approved primers and probes along with our ultra-specific primers and probe for RNase P RNA. Based on bioinformatics analysis, the attachment sites of the CDC-approved primers and probe for endogenous internal control of RNase P are located on the first exon of this gene. In addition to identifying the target gene sequence, these primers and probe also non-specifically detect similar sequences on the genomic DNA. Conclusions: The present study showed that the use of specific primers and probes introduced by CDC for SARS-CoV-2 and influenza virus may cause false results due to non-specific binding to the genomic DNA. Therefore, choosing the right internal control for RNase P RNA can be useful in achieving very accurate results.

Adrenal disease and pregnancy: an overview

Key content Although uncommon, adrenal disorders in pregnancy are associated with severe complications, especially if undiagnosed or poorly managed. Some women are on long‐term steroids (especially those known to suffer from adrenal insufficiency) that suppress endogenous adrenal function. Under stress, these can become insufficient – particularly around labour and the puerperium. Adrenal insufficiency, for example, has been associated with maternal and fetal morbidity and mortality if untreated, while phaeochromocytoma is associated with considerable maternal mortality. Clinical features, diagnosis and management of the disorders of the adrenals in pregnancy are discussed, including Cushing’s syndrome, adrenal insufficiency, phaeochromocytoma and paragangliomas, primary aldosteronism and congenital adrenal hyperplasia. Learning objectives To understand the physiological changes in the adrenal system during pregnancy. To understand the clinical features of common adrenal problems in pregnancy and how they can be diagnosed and managed to minimise complications, especially acute adrenal insufficiency. To understand how the management of adrenal disorders is altered in pregnancy and the effect of adrenal diseases on pregnancy. Ethical issues Is there a role for in utero therapy if a prenatal diagnosis is made? Does treatment of the mother affect the fetus? Is optimal treatment of the mother limited by concerns for the fetus?

Increased Endogenous GDNF in Mice Protects Against Age-Related Decline in Neuronal Cholinergic Markers.

Gradual decline in cholinergic transmission and cognitive function occurs during normal aging, whereas pathological loss of cholinergic function is a hallmark of different types of dementia, including Alzheimer’s disease (AD), Lewy body dementia (LBD), and Parkinson’s disease dementia (PDD). Glial cell line-derived neurotrophic factor (GDNF) is known to modulate and enhance the dopamine system. However, how endogenous GDNF influences brain cholinergic transmission has remained elusive. In this study, we explored the effect of a twofold increase in endogenous GDNF (Gdnf hypermorphic mice, Gdnfwt/hyper) on cholinergic markers and cognitive function upon aging. We found that Gdnfwt/hyper mice resisted an overall age-associated decline in the cholinergic index observed in the brain of Gdnfwt/wt animals. Biochemical analysis revealed that the level of nerve growth factor (NGF), which is important for survival and function of central cholinergic neurons, was significantly increased in several brain areas of old Gdnfwt/hyper mice. Analysis of expression of genes involved in cholinergic transmission in the cortex and striatum confirmed modulation of cholinergic pathways by GDNF upon aging. In line with these findings, Gdnfwt/hyper mice did not undergo an age-related decline in cognitive function in the Y-maze test, as observed in the wild type littermates. Our results identify endogenous GDNF as a potential modulator of cholinergic transmission and call for future studies on endogenous GDNF function in neurodegenerative disorders characterized by cognitive impairments, including AD, LBD, and PDD.

Isthmin-1 is an adipokine that promotes glucose uptake and improves glucose tolerance and hepatic steatosis

With the increasing prevalence of type 2 diabetes and fatty liver disease, there is still an unmet need to better treat hyperglycemia and hyperlipidemia. Here, we identify isthmin-1 (Ism1) as an adipokine and one that has a dual role in increasing adipose glucose uptake while suppressing hepatic lipid synthesis. Ism1 ablation results in impaired glucose tolerance, reduced adipose glucose uptake, and reduced insulin sensitivity, demonstrating an endogenous function for Ism1 in glucose regulation. Mechanistically, Ism1 activates a PI3K-AKT signaling pathway independently of the insulin and insulin-like growth factor receptors. Notably, while the glucoregulatory function is shared with insulin, Ism1 counteracts lipid accumulation in the liver by switching hepatocytes from a lipogenic to a protein synthesis state. Furthermore, therapeutic dosing of recombinant Ism1 improves diabetes in diet-induced obese mice and ameliorates hepatic steatosis in a diet-induced fatty liver mouse model. These findings uncover an unexpected, bioactive protein hormone that might have simultaneous therapeutic potential for diabetes and fatty liver disease.

CYP2E1 in Alcoholic and Non-Alcoholic Liver Injury. Roles of ROS, Reactive Intermediates and Lipid Overload.

CYP2E1 is one of the fifty-seven cytochrome P450 genes in the human genome and is highly conserved. CYP2E1 is a unique P450 enzyme because its heme iron is constitutively in the high spin state, allowing direct reduction of, e.g., dioxygen, causing the formation of a variety of reactive oxygen species and reduction of xenobiotics to toxic products. The CYP2E1 enzyme has been the focus of scientific interest due to (i) its important endogenous function in liver homeostasis, (ii) its ability to activate procarcinogens and to convert certain drugs, e.g., paracetamol and anesthetics, to cytotoxic end products, (iii) its unique ability to effectively reduce dioxygen to radical species causing liver injury, (iv) its capability to reduce compounds, often generating radical intermediates of direct toxic or indirect immunotoxic properties and (v) its contribution to the development of alcoholic liver disease, steatosis and NASH. In this overview, we present the discovery of the enzyme and studies in humans, 3D liver systems and genetically modified mice to disclose its function and clinical relevance. Induction of the CYP2E1 enzyme either by alcohol or high-fat diet leads to increased severity of liver pathology and likelihood to develop ALD and NASH, with subsequent influence on the occurrence of hepatocellular cancer. Thus, fat-dependent induction of the enzyme might provide a link between steatosis and fibrosis in the liver. We conclude that CYP2E1 has many important physiological functions and is a key enzyme for hepatic carcinogenesis, drug toxicity and liver disease.