Macroautophagy inhibition maintains fragmented mitochondria to foster T cell receptor-dependent apoptosis.

Mitochondrial dynamics and functionality are linked to the autophagic degradative pathway under several stress conditions. However, the interplay between mitochondria and autophagy upon cell death signalling remains unclear. The T-cell receptor pathway signals the so-called activation-induced cell death (AICD) essential for immune tolerance regulation. Here, we show that this apoptotic pathway requires the inhibition of macroautophagy. Protein kinase-A activation downstream of T-cell receptor signalling inhibits macroautophagy upon AICD induction. This leads to the accumulation of damaged mitochondria, which are fragmented, display remodelled cristae and release cytochrome c, thereby driving apoptosis. Autophagy-forced reactivation that clears the Parkin-decorated mitochondria is as effective in inhibiting apoptosis as genetic interference with cristae remodelling and cytochrome c release. Thus, upon AICD induction regulation of macroautophagy, rather than selective mitophagy, ensures apoptotic progression.

Identifying and costing common gaps in Central and West Africa pharmaceutical regulation.

Background: Regulatory systems strengthening is crucial for catalyzing access to safe and effective medical products and health technologies (MPHT) for all. Identifying and addressing common regulatory gaps through regional approaches could be instrumental for the newly incepted African Medicine Agency. Aims: This original study sheds light on common gaps among 10 national regulatory authorities (NRAs) and ways to address them regionally. Objectives: The study used NRA self-assessment outcomes to identify common gaps in four critical regulatory pillars and estimate the cost of addressing them from regional perspectives that aimed at raising the maturity level of regulatory institutions. Methods: A cross-sectional study, using the WHO Global Benchmarking Tool (GBT), was conducted between 2020 and 2021 with five NRAs from ECCAS and ECOWAS member states that use French and Spanish as lingua franca. Results: The 10 NRAs operated in a non-formal-to-reactive approach (ML1-2), which hinders their ability to ensure the quality of MPHT and respond appropriately to public health emergencies. Common gaps were identified in four critical regulatory pillars-good regulatory practices, preparedness for public health emergencies, quality management systems, and substandard and falsified medical products-with overall cost to address gaps estimated at US$3.3 million. Contribution: We elaborated a reproducible method to strengthen regulatory systems at a regional level to improve equitable access to assured-quality MPHT. Our bottom-up approach could be utilized by RECs to address common gaps through common efforts.

3-hydroxy 3-methylglutaryl coenzyme A reductase inhibition impairs muscle regeneration.

Skeletal muscle has the ability to regenerate new muscle fibers after injury. The process of new muscle formation requires that quiescent mononuclear muscle precursor cells (myoblasts) become activated, proliferate, differentiate, and fuse into multinucleated myotubes which, in turn, undergo further differentiation and mature to form functional muscle fibers. Previous data demonstrated the crucial role played by 3-hydroxy 3-methylglutaryl coenzyme A reductase (HMGR), the rate-limiting enzyme of cholesterol biosynthetic pathway, in fetal rat myoblast (L6) differentiation. This finding, along with epidemiological studies assessing the myotoxic effect of statins, HMGR inhibitors, allowed us to speculate that HMGR could be strongly involved in skeletal muscle repair. Thus, our research was aimed at evaluating such involvement: in vitro and in vivo experiments were performed on both mouse adult satellite cell derived myoblasts (SCDM) and mouse muscles injured with cardiotoxin. Results demonstrate that HMGR inhibition by the statin Simvastatin reduces SCDM fusion index, fast MHC protein levels by 60% and slow MHC by 40%. Most importantly, HMGR inhibition delays skeletal muscle regeneration in vivo. Thus, besides complaining of myopathies, patients given Simvastatin could also undergo an impairment in muscle repair.

Effects of myosin heavy chain (MHC) plasticity induced by HMGCoA-reductase inhibition on skeletal muscle functions.

The rate-limiting step of cholesterol biosynthetic pathway is catalyzed by 3-hydroxy-3-methylglutaryl coenzyme reductase (HGMR), whose inhibitors, the statins, widely used in clinical practice to treat hypercholesterolemia, often cause myopathy, and rarely rhabdomyolysis. All studies to date are limited to the definition of statin-induced myotoxicity omitting to investigate whether and how HMGR inhibition influences muscle functions. To this end, 3-mo-old male rats (Rattus norvegicus) were treated for 3 wk with a daily intraperitoneal injection of simvastatin (1.5 mg/kg/d), and biochemical, morphological, mechanical, and functional analysis were performed on extensor digitorum longus (EDL) muscle. Our results show that EDL muscles from simvastatin-treated rats exhibited reduced HMGR activity; a 15% shift from the fastest myosin heavy-chain (MHC) isoform IIb to the slower IIa/x; and reduced power output and unloaded shortening velocity, by 41 and 23%, respectively, without any change in isometric force and endurance. Moreover, simvastatin-treated rats showed a decrease of maximum speed reached and the latency to fall off the rotaroad (∼-30%). These results indicate that the molecular mechanism of the impaired muscle function following statin treatment could be related to the plasticity of fast MHC isoform expression.

Age- and sex-related differences in extra-hepatic low-density lipoprotein receptor.

To determine whether differences in LDLr behavior in extra-hepatic tissues and whether extra-hepatic receptors could differentially contribute to cholesterol homeostasis under physiological conditions, we evaluated the presence and regulation of LDLr from both a gender and an aging perspective. We used the brain cortex, the gastrocnemius, and the heart ventricle of 3- and 12-month-old male and female rats. We observed a protein decrease of total LDLr in 12-month-old female rat brains that was completely restored by 17-ß estradiol treatment. In the gastrocnemius, LDLr accumulates in the skeletal muscle in both male and female aged rats as a precursor probably due to a glycosylation impairment. In the heart, no modifications were observed in either older rats or rats of a specific gender. These data highlight a tissue-specific dysregulation of LDLr that is age- and gender-dependent.

Potential role of nonstatin cholesterol lowering agents.

Although statins, 3ß-hydroxy-3ß-methylglutaryl coenzyme A reductase (HMGR) inhibitors, have revolutionized the management of cardiovascular diseases by lowering serum low density lipoproteins, many patients suffer from their side effects. Whether the statin side effects are related to their intrinsic toxicity or to the decrease of HMGR main isoprenoid end products, which are essential compounds for cell viability, is still debated. In addition to HMGR, the key and rate limiting step of cholesterol synthesis, many enzymes are involved in this multi-step pathway whose inhibition could be taken into account for a "nonstatin approach" in the management of hypercholesterolemia. In particular, due to their unique position downstream from HMGR, the inhibition of squalene synthase, farnesyl diphosphate farnesyltransferase (FDFT1), squalene epoxidase (SQLE), and oxidosqualene cyclase:lanosterol synthase (OSC) should decrease plasma levels of cholesterol without affecting ubiquinone, dolichol, and isoprenoid metabolism. Thus, although FDFT1, SQLE and OSC are little studied, they should be considered as perspective targets for the development of novel drugs against hypercholesterolemia. Here, structure-function relationships of FDFT1, SQLE, and OSC are reviewed highlighting the advantages that the downstream inhibition of HMGR could provide when compared to the statin-based therapy.

Mechanism underlying long-term regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase during L6 myoblast differentiation.

3-Hydroxy 3-methylglutaryl Coenzyme A reductase (HMG-CoAR) and its end-products are crucial for insulin-induced differentiation of fetal rat myoblasts (L6) both at early and terminal stages of development. Inhibition of HMG-CoAR activity and reduction of the enzyme levels impair the expression of L6 differentiation markers and prevent myoblast fusion into multinucleated syncytia. The mechanism underlying the modulation of this crucial enzyme so that muscular differentiation can occur is poorly understood. Thus, the aim of this work was to explore the long-term regulation of HMG-CoAR in an attempt to provide a new molecular basis for the control of muscle development. All experiments were performed in L6 rat myoblasts induced to differentiate utilizing insulin. The results indicate the following: (i) at early stages of L6 differentiation, the increase in HMG-CoAR protein levels is probably due to transcriptional induction and a decrease in the enzyme degradation rate; (ii) the subsequent reduction of HMG-CoAR protein levels is related both to an increased degradation rate and reduced gene transcription, as indicated by the rise of Insig-1 levels and the subsequent decrease in the amount of n-SREBP-1; (iii) in the terminal stages of myogenesis, reduced protein levels of HMG-CoAR could be ascribed to the decrease in gene transcription while its degradation rate is not affected. By highlighting the mechanisms involved in HMG-CoAR long-term regulation during myogenesis, this work provides useful information for searching for tools to improve the regenerative ability of muscle tissue and for the development of new pharmacological treatments of myopathies.

3-hydroxy 3-methylglutaryl coenzyme A reductase increase is essential for rat muscle differentiation.

3-Hydroxy 3-methylglutaryl coenzyme A reductase (HMG-CoAR) is the key and rate-limiting enzyme of cholesterol biosynthetic pathway. Although HMG-CoAR activity has already been related to the differentiation of some cellular lines there are no studies that analyze the role of HMG-CoAR, and the pathway it is involved with in a fully characterized muscle differentiation model. Thus, the aim of this work is to evaluate such role and delineate the pathway involved in foetal rat myoblasts (L6) induced to differentiate by insulin -- a standard and feasible model of the myogenic process. The results obtained by biochemical and morphological approaches demonstrate that (i) HMG-CoAR increase is crucial for differentiation induction, (ii) p21waf, whose increase is a necessary requisite for differentiation to occur, rises downstream HMG-CoAR activation, (iii) the main role of p38/MAPK as key regulator also for HMG-CoAR. Pathologies characterized by muscle degeneration might benefit from therapeutic programmes committed to muscle function restoration, such as modulation and planning myoblast differentiation. Thus, the important role of HMG-CoAR in muscular differentiation providing new molecular basis for the control of muscle development can help in the design of therapeutic treatment for diseases characterized by the weakening of muscular fibers and aging-related disorders (sarcopenia).

Hypercholesterolemia and 3-hydroxy 3-methylglutaryl Coenzyme A reductase regulation during ageing.

We present here a brief description of the path that cholesterol covers from its intestinal absorption to its effect exerted on some enzyme regulation. Some mechanisms underlying hypercholesterolemia onset and, in particular, the role and the regulation of 3-hydroxy 3-methylglutaryl Coenzyme A reductase (HMGR) during adult life and during aging, have been described. In addition some pharmacological interventions to control proper HMGR regulation and, in turn, cholesterol homeostasis maintenance will be introduced.

Cholesterol homeostasis failure in the brain: implications for synaptic dysfunction and cognitive decline.

Cholesterol is one of the most important molecules in cell physiology because of its involvement in several biological processes: for instance, it determines both physical and biochemical properties of cell membranes and proteins. Disruption to cholesterol homeostasis leads to coronary heart disease, atherosclerosis and metabolic syndrome. Strong evidence suggests that cholesterol also has a crucial role in the brain as various neurological and neurodegenerative disorders, including Alzheimer's, Huntington's and Parkinson diseases are associated with disruptions to cholesterol homeostasis. Here, we summarize the current knowledge about the role cholesterol plays at synaptic junctions and the pathological consequences caused by disruptions in the homeostatic maintenance of this compound.

Cholesterol metabolism is altered in Rett syndrome: a study on plasma and primary cultured fibroblasts derived from patients.

Rett (RTT) syndrome is a severe neurological disorder that affects almost exclusively females. Several detectable mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2) are responsible for the onset of the disease. MeCP2 is a key transcription regulator involved in gene silencing via methylation-dependent remodeling of chromatin. Recent data highlight that lipid metabolism is perturbed in brains and livers of MECP2-null male mice. In addition, altered plasma lipid profile in RTT patients has been observed. Thus, the aim of the work is to investigate the protein network involved in cholesterol homeostasis maintenance on freshly isolated fibroblasts and plasma from both RTT and healthy donors. To this end, protein expression of 3-hydroxy-3methyl glutaryl Coenzyme A reductase (HMGR), sterol regulatory element binding proteins (SREBPs), low density lipoprotein receptor (LDLr) and scavenger receptor B-1 (SRB-1) was assessed in cultured skin fibroblasts from unaffected individuals and RTT patients. In addition, lipid profile and the abundance of proprotein convertase subtilisin/kexin type 9 (PCSK9) were analyzed on plasma samples. The obtained results demonstrate that the main proteins belonging to cholesterol regulatory network are altered in RTT female patients, providing the proof of principle that cholesterol metabolism may be taken into account as a new target for the treatment of specific features of RTT pathology.

New compounds able to control hepatic cholesterol metabolism: Is it possible to avoid statin treatment in aged people?

Aging is characterized by the loss of homeostasis that leads to changes in the biochemical composition of tissues, reduced ability to respond adaptively to environmental stimuli, and increased susceptibility and vulnerability to diseases including coronary artery diseases, carotid artery disease and brain vessel disease. Hypercholesterolemia is one of the primary risk factors for these pathologies, whose incidence is highly related to aging. Almost 25% of men and 42% of women older than 65 years have a serum total cholesterol level greater than 240 mg/dL. The mechanisms behind this age-related increase in plasma cholesterol are still incompletely understood, thus, the control of plasma cholesterol content in aged people is more challenging than in adults. In this review the different pharmacological approaches to reduce plasma cholesterol levels, particularly in aged people, will be discussed. In brief, current therapies are mostly based on the prescription of statins (3-hydroxy-3-methylglutaryl-CoA reductase inhibitors) that are pretty effective but that exert several side effects. More attention should be given to potential drug interactions, potential age-related changes in drug pharmacokinetics, adverse effects such as myopathy and competing risks when statins are prescribed to old patients. In combination or in alternative to statin therapy, other agents might be required to reduce low density lipoprotein (LDL) cholesterol levels. Among the available drugs, the most commonly prescribed are those addressed to reduce cholesterol absorption, to modulate lipoprotein lipase activity and bile acid sequestrants: even these pharmacological interventions are not exempt from side effects. The use of antioxidants or organoselenium compounds and the discovery of new proteins able to modulate exclusively LDL receptor recycling such as Proprotein convertase subtilisin kexin 9 and SEC24 offer new pharmacological approaches to selectively reduce the main causes of dyslipidemia.

Regulation and deregulation of cholesterol homeostasis: The liver as a metabolic "power station".

Cholesterol plays several structural and metabolic roles that are vital for human biology. It spreads along the entire plasma membrane of the cell, modulating fluidity and concentrating in specialized sphingolipid-rich domains called rafts and caveolae. Cholesterol is also a substrate for steroid hormones. However, too much cholesterol can lead to pathological pictures such as atherosclerosis, which is a consequence of the accumulation of cholesterol into the cells of the artery wall. The liver is considered to be the metabolic power station of mammalians, where cholesterol homeostasis relies on an intricate network of cellular processes whose deregulations can lead to several life-threatening pathologies, such as familial and age-related hypercholesterolemia. Cholesterol homeostasis maintenance is carried out by: biosynthesis, via 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity; uptake, through low density lipoprotein receptors (LDLr); lipoprotein release in the blood; storage by esterification; and degradation and conversion into bile acids. Both HMGR and LDLr are transcribed as a function of cellular sterol amount by a family of transcription factors called sterol regulatory element binding proteins that are responsible for the maintenance of cholesterol homeostasis through an intricate mechanism of regulation. Cholesterol obtained by hepatic de novo synthesis can be esterified and incorporated into apolipoprotein B-100-containing very low density lipoproteins, which are then secreted into the bloodstream for transport to peripheral tissues. Moreover, dietary cholesterol is transferred from the intestine to the liver by high density lipoproteins (HDLs); all HDL particles are internalized in the liver, interacting with the hepatic scavenger receptor (SR-B1). Here we provide an updated overview of liver cholesterol metabolism regulation and deregulation and the causes of cholesterol metabolism-related diseases. Moreover, current pharmacological treatment and novel hypocholesterolemic strategies will also be introduced.

Short- and long-term regulation of 3-hydroxy 3-methylglutaryl coenzyme A reductase by a 4-methylcoumarin.

Dyslipidemia is one of the most significant risk factors for cardiovascular diseases. Cholesterol homeostasis is regulated by both the receptor-mediated endocytosis of Low Density Lipoproteins by LDL receptors and de novo cholesterol synthesis via the rate-limiting enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase. Although statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase substrate competitors, have revolutionized the management of cardiovascular diseases by lowering serum LDL, their side effects range from myalgia to rhabdomyolysis. Treatment with antioxidant compounds could represent an efficient alternative in the modulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity. Indeed it has already been demonstrated that the rise in reactive oxygen species levels causes the complete dephosphorylation and, in turn activation of the enzyme. Many coumarins and their derivatives have the special ability to scavenge reactive oxygen species or show a lipid lowering potential. Here we evaluated whether the coumarin, 4-methylesculetin could exert both the ability to scavenge ROS and to modulate 3-hydroxy-3-methylglutaryl coenzyme A reductase in HepG2 cell line where the enzyme activity dysregulation induced by reactive oxygen species has already been reported. The antioxidant property of 4-methylesculetin led to the reduction of 3-hydroxy-3-methylglutaryl coenzyme A reductase activation state through the increase of the enzyme phosphorylation. In addition, this coumarin showed the ability to modulate 3-hydroxy-3-methylglutaryl coenzyme A reductase protein levels both by transcriptional and degradational events independent of its antioxidant activity.

Age-Related Hypercholesterolemia and HMG-CoA Reductase Dysregulation: Sex Does Matter (A Gender Perspective).

Although cardiovascular diseases are less prevalent in premenopausal women than in men, their occurrence in women increases at the onset of menopause, and the loss of female sex hormones contributes to the striking increase in cardiovascular morbidity and mortality in postmenopausal women. We present here a description of age-related disruption of lipid homeostasis, which particularly affects 3-hydroxy 3-methylglutaryl Coenzyme A reductase, the key rate-limiting enzyme in the cholesterol biosynthetic pathway. We further discuss the age- and gender-related dysregulation of this enzyme, providing new evidence for the different mechanisms driving dyslipidemia in elderly men and women. In addition, we introduce pharmacological methods of regulating HMGR and maintaining cholesterol homeostasis.

Hypercholesterolemia and 3-hydroxy-3-methylglutaryl coenzyme A reductase regulation in aged female rats.

Coronary heart disease is less prevalent in pre-menopausal women than in men, but increases at the onset of menopause. This delay is due to estrogen protective effects. The rise of cholesterolemia is one of the main risk factors for coronary disease. Since 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is the rate-limiting enzyme of the cholesterol biosynthetic pathway, it plays a pivotal role in cholesterol homeostasis maintenance. Aim of this study is to investigate whether HMGR is involved in the cholesterolemia increase that occurs during aging, and to consider its potential role as a target for estrogen protective effects. "In vivo" studies have been performed using the livers of 12-month-old female rats (whose estrogen level decrease is comparable to the one detected at the occurrence of human menopause), 12-month-old female rats treated with 17-beta-estradiol, and 3-month-old untreated male and female rats. The results indicated hypercholesterolemic status and a significant increase of HMGR activity according to a reduced activation of AMPK detected in treated rats compared to controls. Furthermore, 17-beta estradiol treatment reduced HMGR activity restoring AMPK activation. These findings highlight the correlation between estrogen and HMGR short-term regulation, and suggest the presence of another mechanism underlying the protective role of estrogen in age-related diseases.

OCT y nuevas técnicas diagnósticas en la evaluación del glaucoma / OCT and new diagnostic techniques in glaucoma evaluation

Desde su descripción inicial hace sólo 15 años la Tomografía de Coherencia óptica (OCT} ha emergido como una herramienta crítica de diagnóstico en el manejo de los pacientes con enfermedades vitreorretinianas. De manera similar al ultrasonido que emplea ecos para identificar las estructuras, la OCT detecta las interfases tisulares en el ojo, midiendo el retraso en la luz reflejada como resultado de los cambios en el índice de refracción de los tejidos. Un punto único de luz reflejado desde la retina forma la que se llama un modo A y contiene información de alta resolución ( < lO um} acerca de la ubicación axial de las interfases tisulares dentro del ojo. Estos puntos únicos de luz pueden ser alineados lateralmente para conformar las imágenes modo B que son las empleadas comúnmente en la clínica. Los equipos más nuevos pueden conformar cubos de información densa tridimensional, capturando muchos barridos modo B en rápida sucesión (OCT Tridimensional}. Los datos tridimensionales pueden luego ser vistos de frente como un "modo C" o en cualquier orientación o dirección con el propósito de visualizar regiones específicas del fondo de ojo. La Tomografía de Coherencia Óptica es una técnica de exploración reproducible y no invasiva que permite obtener imágenes de secciones transversales del ojo con alta resolución. Esta tecnología proporciona mediciones cuantitativas de la capa de fibras nerviosas peripapilares y de la mácula, y mediciones topográficas de la cabeza del nervio óptico. Estas mediciones pueden utilizarse en el diagnóstico, evaluación y tratamiento del glaucoma y de la patología retiniana.