Skeletal muscle atrophy after sciatic nerve damage: Mechanistic insights.

Sciatic nerve injury leads to molecular events that cause muscular dysfunction advancement in atrophic conditions. Nerve damage renders muscles permanently relaxed which elevates intracellular resting Ca2+ levels. Increased Ca2+ levels are associated with several cellular signaling pathways including AMPK, cGMP, PLC-ß, CERB, and calcineurin. Also, multiple enzymes involved in the tricarboxylic acid cycle and oxidative phosphorylation are activated by Ca2+ influx into mitochondria during muscle contraction, to meet increased ATP demand. Nerve damage induces mitophagy and skeletal muscle atrophy through increased sensitivity to Ca2+-induced opening of the permeability transition pore (PTP) in mitochondria attributed to Ca2+, ROS, and AMPK overload in muscle. Activated AMPK interacts negatively with Akt/mTOR is a highly prevalent and well-described central pathway for anabolic processes. Over the decade several reports indicate abnormal behavior of signaling machinery involved in denervation-induced muscle loss but end up with some controversial outcomes. Therefore, understanding how the synthesis and inhibitory stimuli interact with cellular signaling to control muscle mass and morphology may lead to new pharmacological insights toward understanding the underlying mechanism of muscle loss after sciatic nerve damage. Hence, the present review summarizes the existing literature on denervation-induced muscle atrophy to evaluate the regulation and expression of differential regulators during sciatic damage.

Correction: DNA replication protein Cdc45 directly interacts with PCNA via its PIP box in Leishmania donovani and the Cdc45 PIP box is essential for cell survival.

[This corrects the article DOI: 10.1371/journal.ppat.1008190.].

Integrated omics analysis revealed the Tinospora cordifolia intervention modulated multiple signaling pathways in hypertriglyceridemia patients-a pilot clinical trial.

Purpose: Hypertriglyceridemia (HTG) is strongly associated with the various types of disease conditions and evolving as epidemics. Hence, it is important to identify molecules that lower the triglyceride and chylomicron levels. Tinospora cordifolia is an illustrious Ayurveda drug, has proved juvenile and immunomodulatory properties. Methods: Twenty four (24) patients having >499 mg/dL TG and 130-230 mg/dL of cholesterol were randomized and given 100 mL/day (~3.0 g) water extract of T. cordifolia (TCE) for 14 days. Basal parameters were analyzed before and after TC intervention to analyzed primary outcomes. Further, unbiased metabolomics and proteomics profiling was explored to assess the efficacy of TCE in HTG patients. Results: TCE intervention decreased the levels of triglycerides, and VLDL to 380.45 ± 17.44, and 31.85 ± 5.88, and increased the HDL levels to 47.50 ± 9.05 mg/dL significantly (p < 0.05). Metabolomics analysis identified the significant alteration in 69 metabolites and 72 proteins in plasma of HTG patients. TCE intervention reduced the level of isoprostanes, ROS, BCAA, and fatty acid derivatives, significantly. The annotation databases, Metboanalyst predicted Akt and Rap1 signaling, and ECM-receptor interaction is the most affected in HTG patients. TCE intervention normalized these events by increasing the peroxisome biogenesis and modulating Akt and Rap1 signaling pathway. Conclusion: T. cordifolia intervention suppresses the baseline in HTG patients. Omics analysis showed that TCE intervention modulates the Akt and Rap signaling, and peroxisome biogenesis to control the cellular switches and signaling pathways. Hence, TCE can be used as a supplement or alternate of standard drugs being used in the management of HTG. Supplementary Information: The online version contains supplementary material available at 10.1007/s40200-022-00985-6.

Natural products: Potential therapeutic agents to prevent skeletal muscle atrophy.

The skeletal muscle (SkM) is the largest organ, which plays a vital role in controlling musculature, locomotion, body heat regulation, physical strength, and metabolism of the body. A sedentary lifestyle, aging, cachexia, denervation, immobilization, etc. Can lead to an imbalance between protein synthesis and degradation, which is further responsible for SkM atrophy (SmA). To date, the understanding of the mechanism of SkM mass loss is limited which also restricted the number of drugs to treat SmA. Thus, there is an urgent need to develop novel approaches to regulate muscle homeostasis. Presently, some natural products attained immense attraction to regulate SkM homeostasis. The natural products, i.e., polyphenols (resveratrol, curcumin), terpenoids (ursolic acid, tanshinone IIA, celastrol), flavonoids, alkaloids (tomatidine, magnoflorine), vitamin D, etc. exhibit strong potential against SmA. Some of these natural products have been reported to have equivalent potential to standard treatments to prevent body lean mass loss. Indeed, owing to the large complexity, diversity, and slow absorption rate of bioactive compounds made their usage quite challenging. Moreover, the use of natural products is controversial due to their partially known or elusive mechanism of action. Therefore, the present review summarizes various experimental and clinical evidence of some important bioactive compounds that shall help in the development of novel strategies to counteract SmA elicited by various causes.

Efficacy of Flavonoids in Combating Fluconazole Resistant Oral Candidiasis.

BACKGROUND: Candida is an opportunistic fungus often present in the oral mucosa. In the compromised immune system, it may become pathogenic and cause oral candidiasis. This infection is more common with Candida albicans; though, non-albicans Candida spp also have significant relevance. Current treatment guidelines include polyenes, azoles and echinocandins, where fluconazole is the primary therapeutic option. However, both inherited and acquired resistance to fluconazole is exhaustively reported. The development of resistance has resulted in the worsening of the original and re-emergence of new fungal diseases. Thus, the development of an anti-candidiasis therapy with a satisfactory outcome is the urgent need of the hour. OBJECTIVE: This review article aims to stimulate research in establishing the synergistic efficacy of various flavonoids with fluconazole to combat the resistance and develop an effective pharmacotherapy for the treatment of oral candidiasis. Further, in this article, we discuss in detail the mechanisms of action of fluconazole, along with the molecular basis of the development of resistance in Candida species. METHODS: PubMed and other databases were used for literature search. RESULTS: The designing of natural drugs from the plant-derived phytochemicals are the promising alternatives in modern medicine. The challenge today is the development of alternative anti-oral candidiasis drugs with increased efficacy, bioavailability and better outcome which can combat azole resistance. Identifying the flavonoids with potential antifungal action at low concentrations seems to meet the challenges. CONCLUSION: Phyto-active constituents, either alone or in combination with conventional antibiotics may be an effective approach to deal with global antimicrobial resistance. The efficacy of herbal therapy for decades suggests that bacteria, fungi, and viruses may have a reduced ability to adapt and resistance to these natural antimicrobial regimes.

S-nitrosoglutathione alleviates hyperglycemia-induced neurobehavioral deficits involving nitro-oxidative stress and aberrant monaminergic system.

The present study evaluated the protective role of S-nitrosoglutathione (GSNO) in preventing hyperglycemia-induced nitro-oxidative stress and alterations in monoaminergic system associated with neurobehavioral deficits in mice. Mice were subjected to diabetes by intraperitoneal injection of streptozotocin (40 mg/kg body weight) for 5 days, whereas GSNO (100 µg/kg body weight) was administered daily via oral route for 8 weeks. Diabetic mice showed deficits in neurobehavioral functions associated with memory, learning, anxiety and motor coordination. These neurobehavioral deficits observed in diabetic mice may be attributed to decrease in norepinephrine (NE), dopamine (DA), serotonin (5-HT) and increased monoamine oxidase (MAO) activity in cortex and hippocampus. Further, a significant increase in reactive oxygen species (ROS), protein carbonyls, nitrotyrosine (NT) and lipid peroxidation were observed in brain regions of diabetic animals suggesting increased nitro-oxidative stress. Hyperglycemia induced nitro-oxidative stress appears to involve reduction in redox ratio (GSH/GSSG) and enzymatic antioxidants; catalase (CAT) and superoxide dismutase (SOD) in cortex and hippocampus. However, GSNO supplementation was able to ameliorate alterations in monoaminergic system and nitro-oxidative stress in the brain regions thereby restoring neurobehavioural functions. These findings suggest GSNO as potential therapeutic molecule to prevent diabetic encephalopathy.

Dynamics and Interplay between Autophagy and Ubiquitin-proteasome system Coordination in Skeletal Muscle Atrophy.

Skeletal muscles are considered the largest reservoirs of the protein pool in the body and are critical for the maintenances of body homeostasis. Skeletal muscle atrophy is supported by various physiopathological conditions that lead to loss of muscle mass and contractile capacity of the skeletal muscle. Lysosomal mediated autophagy and ubiquitin-proteasomal system (UPS) concede the major intracellular systems of muscle protein degradation that result in the loss of mass and strength. Both systems recognize ubiquitination as a signal of degradation through different mechanisms, a sign of dynamic interplay between systems. Hence, growing shreds of evidence suggest the interdependency of autophagy and UPS in the progression of skeletal muscle atrophy under various pathological conditions. Therefore, understanding the molecular dynamics and associated factors responsible for their interdependency is necessary for the new therapeutic insights to counteract muscle loss. Based on current literature, the present review summarizes the factors that interplay between autophagy and UPS in favor of enhanced proteolysis of skeletal muscle and how they affect the anabolic signaling pathways under various conditions of skeletal muscle atrophy.

The dependency of autophagy and ubiquitin proteasome system during skeletal muscle atrophy.

Among the four proteolytic systems in the cell, autophagy and the ubiquitin-proteasome system (UPS) are the main proteolytic events that allow for the removal of cell debris and proteins to maintain cellular homeostasis. Previous studies have revealed that these systems perform their functions independently of each other. However, recent studies indicate the existence of regulatory interactions between these proteolytic systems via ubiquitinated tags and a reciprocal regulation mechanism with several crosstalk points. UPS plays an important role in the elimination of short-lived/soluble misfolded proteins, whereas autophagy eliminates defective organelles and persistent insoluble protein aggregates. Both of these systems seem to act independently; however, disruption of one pathway affects the activity of the other pathway and contributes to different pathological conditions. This review summarizes the recent findings on direct and indirect dependencies of autophagy and UPS and their execution at the molecular level along with the important drug targets in skeletal muscle atrophy.

Dynamics of Toll-like Receptors Signaling in Skeletal Muscle Atrophy.

Skeletal muscle atrophy has been characterized as a state of uncontrolled inflammation and oxidative stress that escalates protein catabolism. Recent advancement supports impinging signaling molecules in the muscle fibers controlled through toll-like receptors (TLR). Activated TLR signaling pathways have been identified as inhibitors of muscle mass and provoke the settings for muscle atrophy. Among them, mainly TLR2 and TLR4 manifest their presence to exacerbate the release of the pro-inflammatory cytokine to deform the synchronized muscle programming. The present review enlightens the TLR signaling mediated muscle loss and the interplay between inflammation and skeletal muscle growth.

Magnoflorine prevent the skeletal muscle atrophy via Akt/mTOR/FoxO signal pathway and increase slow-MyHC production in streptozotocin-induced diabetic rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Tinospora cordifolia (TC) is being used as a blood purifier in Ayurveda since ancient time. It is a very popular immunomodulator and holds anti-inflammatory and anti-oxidative potential, hence anti-aging properties. Therefore, it is also known as 'Amrita' in Ayurveda and is widely used to treat diabetes mellitus type II (T2DM) and its secondary complications; however, its underlying mechanism was not expedited to date. AIM-: To explore the in vivo therapeutic efficiency and mechanism of action of TC and its secondary constitute magnoflorine on the skeletal muscle atrophy in the rat model of T2DM. METHOD: Animal model of T2DM was developed using streptozotocin (STZ) injection followed by intervention with TC, metformin, and magnoflorine for three weeks. Confirmation of T2DM and abrogation of atrophic markers and possible mechanisms on supplementation of TC and magnoflorine were explored using histology, bio-assays, Western blotting, and q-PCR. RESULT: TC and Magnoflorine supplementations significantly (p ≤ 0.05) decreased the fasting blood glucose (FBG) levels in T2DM rats. Both treatments prevented the lean body, individual skeletal muscle mass, and myotubes diameter loss (p ≤ 0.05). Magnoflorine significantly reduced the degradation of the protein indicated by biochemical markers of atrophy i.e. decreased serum creatine kinase (CK) levels and increased myosin heavy chain-ß (MyHC-ß) levels in muscles. Q-PCR and western blotting supported the findings that magnoflorine significantly increased the mRNA and protein abundances (~3 fold) of MyHC-ß.TC and magnoflorine efficiently decreased the expression of ubiquitin-proteasomal E3-ligases (Fn-14/TWEAK, MuRF1, and Atrogin 1), autophagy (Bcl-2/LC3B), and caspase related genes along with calpains activities in T2DM rats. Both TC and magnoflorine also increased the activity of superoxide dismutase, GSH-Px, decreased the activities of ß-glucuronidase, LPO, and prevented any alteration in the catalase activity. In contrast, magnoflorine increased expression of TNF-α and IL-6 whereas TC and metformin efficiently decreased the levels of these pro-inflammatory cytokines (p ≤ 0.05). However, magnoflorine was found to increase phosphorylation of Akt more efficiently than TC and metformin. CONCLUSION: TC, and magnoflorine are found to be effective to control fasting blood glucose levels significantly in T2DM rats. It also promoted the Akt phosphorylation, suppressed autophagy and proteolysis that might be related to blood glucose-lowering efficacy of magnoflorine and TC. However, increased muscle weight, specifically of the soleus muscle, expression of IL-6, and slow MyHC indicated the increased myogenesis in response to magnoflorine and independent from its hypoglycemic activity.

DNA replication protein Cdc45 directly interacts with PCNA via its PIP box in Leishmania donovani and the Cdc45 PIP box is essential for cell survival.

DNA replication protein Cdc45 is an integral part of the eukaryotic replicative helicase whose other components are the Mcm2-7 core, and GINS. We identified a PIP box motif in Leishmania donovani Cdc45. This motif is typically linked to interaction with the eukaryotic clamp proliferating cell nuclear antigen (PCNA). The homotrimeric PCNA can potentially bind upto three different proteins simultaneously via a loop region present in each monomer. Multiple binding partners have been identified from among the replication machinery in other eukaryotes, and the concerted /sequential binding of these partners are central to the fidelity of the replication process. Though conserved in Cdc45 across Leishmania species and Trypanosoma cruzi, the PIP box is absent in Trypanosoma brucei Cdc45. Here we investigate the possibility of Cdc45-PCNA interaction and the role of such an interaction in the in vivo context. Having confirmed the importance of Cdc45 in Leishmania DNA replication we establish that Cdc45 and PCNA interact stably in whole cell extracts, also interacting with each other directly in vitro. The interaction is mediated via the Cdc45 PIP box. This PIP box is essential for Leishmania survival. The importance of the Cdc45 PIP box is also examined in Schizosaccharomyces pombe, and it is found to be essential for cell survival here as well. Our results implicate a role for the Leishmania Cdc45 PIP box in recruiting or stabilizing PCNA on chromatin. The Cdc45-PCNA interaction might help tether PCNA and associated replicative DNA polymerase to the DNA template, thus facilitating replication fork elongation. Though multiple replication proteins that associate with PCNA have been identified in other eukaryotes, this is the first report demonstrating a direct interaction between Cdc45 and PCNA, and while our analysis suggests the interaction may not occur in human cells, it indicates that it may not be confined to trypanosomatids.

Intervention of Ayurvedic drug Tinospora cordifolia attenuates the metabolic alterations in hypertriglyceridemia: a pilot clinical trial.

PURPOSE: Hypertriglyceridemia (HG) is an independent risk factor with more prevalence than hypercholesterolemia and its attributes to cardiovascular disease (CVD) and pancreatitis. Hence, it becomes imperative to search for new triglyceride (TG) lowering agents. Tinospora cordifolia (TC) is a well-known Ayurvedic drug and a rich source of protoberberine alkaloids hence can contribute to TG lowering without side effects. Hence, to explore the therapeutic efficacy of T. cordifolia and its effects on biochemistry and metabolome in the patients of hyper-triglyceridemia, clinical trials were conducted. METHODS: Patients (n = 24) with hypertriglyceridemia were randomized into two groups to receive T. cordifolia extract (TCE) (3.0 g/per day) and metformin (850 mg/day) for 14 days having >300 mg/dl triglyceride level and cholesterol in the range of 130-230 mg/dl. Lipid profiles of blood samples were analyzed. Urine samples were subjected to HPLC-QTOF-MS to quantify oxidative damage and abnormal metabolic regulation. RESULTS: Intervention with TCE reduced the triglyceride, LDL, and VLDL levels to 380.45 ± 17.44, 133.25 ± 3.18, and 31.85 ± 5.88 mg/dL and increased the HDL to 47.50 ± 9.05 mg/dL significantly (p < 0.05) in the HG patients after 14 days treatment. TCE dosage potently suppressed the inflammatory and oxidative stress marker's i.e. levels of isoprostanes significantly (p < 0.01). Qualitative metabolomics approach i.e. PCA and PLS-DA showed significant alterations (p < 0.05) in the levels of 40 metabolites in the urine samples from different groups. CONCLUSION: TCE administration depleted the levels of markers of HG i.e. VLDL, TG, and LDL significantly. Metabolomics studies established that the anti-HG activity of TCE was due to its antioxidative potential and modulation of the biopterin, butanoate, amino acid, and vitamin metabolism. CLINICAL TRIALS REGISTRY: India (CTRI) registration no. CTRI- 2016-08-007187.

Interactions of a medicinal climber Tinospora cordifolia with supportive interspecific plants trigger the modulation in its secondary metabolic profiles.

Tinospora cordifolia (TC) is scientifically proven immunomodulatory drug being used for centuries. Ancient literature reported that inter-specific interactions change medicinal properties of TC. Thus, the current study is aimed to understand the influence of interspecific biotic interactions on chemo-profiles of TC. To explore it, TC samples collected from six co-occurring plants, i.e. Azarditchita indica, Acacia nilotica, Albezia lebbeck, Ficus benghalensis, Tamarandus indica and Acacia leucophloea were analyzed by HPLC-ESI-QTOF-MS. Mass data were subjected to multivariate analysis. Support vector machines (SVMs) was found to be best classifier (r2 < 0.93). Data analysis showed the specific compounds in all TC due to inter-specific interactions. Data were further analyzed with SNK post-hoc test followed by permutative (n = 50) Bonferroni FDR multiple testing correction. The compound without any missing values reduced the number of variables to 133 (p < 0.01). Statistical analysis revealed that TC having interactions with A.lebbeck and A. nilotica formed the most distant groups. However, TC co-occurred with A. indica showed the highest number of up-regulated metabolites, including jatrorrhizine, chrysin, peonidin, 6-methylcoumarin and some terpenoids. Some metabolites, including jatrorrhizine and magnoflorine were quantified to confirm the accuracy of qualitative analysis. Results demonstrated the influence of inter-specific biotic interactions on TC chemo-profiles, hence its medicinal properties.

Resveratrol loaded solid lipid nanoparticles attenuate mitochondrial oxidative stress in vascular dementia by activating Nrf2/HO-1 pathway.

Vascular dementia (VaD) is the leading cause of cognitive decline resulting from vascular lesions. Recent studies have shown that mitochondrial dysfunctions and oxidative stress are involved in cognitive decline. The aim of the present study was to evaluate the beneficial effects of resveratrol-loaded solid lipid nanoparticles (R-SLNs) in permanent bilateral common carotid artery occlusion (BCCAO) induced model of VaD. R-SLNs prepared had average size of 286 nm and 91.25% drug encapsulation efficiency with sustained release. Moreover, R-SLNs had 4.5 times higher levels of resveratrol (RSV) in brain compared to when administered as free RSV. Neurobehavioral analyses revealed that R-SLNs administration successfully ameliorated cognitive decline observed in BCCAO rats. Administration of R-SLNs to BCCAO animals showed significant reduction in mitochondrial reactive oxygen species (ROS) generation, lipid peroxidation, and protein carbonyls. In addition, R-SLNs significantly improved redox ratio and Mn-superoxide dismutase (Mn-SOD) activity. R-SLNs administration resulted in significant reduction in hypoxia-inducible factor 1α (HIF-1α) levels, whereas, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and heme oxygenase 1 (HO-1) levels were increased after R-SLNs treatment. Taken together, the results demonstrate that R-SLNs could be a novel and promising therapeutic strategy in VaD as well in other age-related neurodegenerative disorders.

Sulforaphane attenuates postnatal proteasome inhibition and improves spatial learning in adult mice.

Proteasomes are known to degrade proteins involved in various processes like metabolism, signal transduction, cell-cycle regulation, inflammation, and apoptosis. Evidence showed that protein degradation has a strong influence on developing neurons as well as synaptic plasticity. Here, we have shown that sulforaphane (SFN) could prevent the deleterious effects of postnatal proteasomal inhibition on spatial reference and working memory of adult mice. One day old Balb/c mice received intracerebroventricular injections of MG132 and SFN. Sham received an equal volume of aCSF. We observed that SFN pre-administration could attenuate MG132 mediated decrease in proteasome and calpain activities. In vitro findings revealed that SFN could induce proteasomal activity by enhancing the expression of catalytic subunit-ß5. SFN pre-administration prevented the hippocampus based spatial memory impairments during adulthood, mediated by postnatal MG132 exposure. Histological examination showed deleterious effects of MG132 on pyramidal neurons and granule cell neurons in DG and CA3 sub-regions respectively. Furthermore, SFN pre-administration has shown to attenuate the effect of MG132 on proteasome subunit-ß5 expression and also induce the Nrf2 nuclear translocation. In addition, SFN pre-administered mice have also shown to induce expression of pCaMKII, pCreb, and mature/pro-Bdnf, molecules which play a crucial role in spatial learning and memory consolidation. Our findings have shown that proteasomes play an important role in hippocampal synaptic plasticity during the early postnatal period and SFN pre-administration could enhance the proteasomal activity as well as improve spatial learning and memory consolidation.

Postnatal Proteasome Inhibition Promotes Amyloid-ß Aggregation in Hippocampus and Impairs Spatial Learning in Adult Mice.

Ubiquitin-proteasome system (UPS) has emerged as major molecular mechanism which modulates synaptic plasticity. However, very little is known about what happens if this system fails during postnatal brain development. In the present study, MG132 was administered intracerebroventricularly in BALB/c mice pups at postnatal day one (P1), a very crucial period for synaptogenesis. Both 20S proteasome and calpain activities were found to be reduced in the mid brain of MG132-administered pups after 24 h. Mice (P40) which received MG132 on P1 were subjected to Morris water maze (MWM) training. Analysis showed spatial learning and memory of MG132 mice was significantly impaired when compared to age-matched controls. Hematoxylin and eosin as well as Cresyl Violet staining revealed substantial loss of cellular connections, distorted architecture and increased pyknosis in hippocampal CA1 and CA3 regions of MG132 mice. Immunohistochemical analysis of MG132 mice showed increased accumulation of intracellular amyloid-ß in hippocampal cells when compared to control. Moreover, double immunostaining revealed increased expression of amyloid precursor protein C-terminal fragments (APP-CTFß) without affecting ß-secretase expression in MG132 mice. Real-Time PCR analyses showed significant increase in hippocampal expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit glutamate A1 (GluA1), but no change in the brain-derived neurotrophic factor (Bdnf) expression in MG132 mice. Western blot analyses showed decreased levels of pThr286-CaMKIIα:CaMKIIα and pSer133-CREB:CREB ratio but increased pro:mature BDNF ratio in the hippocampus of MG132 mice. Taken together, postnatal proteasome inhibition could lead to accumulation of intracellular amyloid-ß protein aggregates, which mediate hippocampus-dependent spatial memory impairments in adult mice.

Cell cycle stage-specific transcriptional activation of cyclins mediated by HAT2-dependent H4K10 acetylation of promoters in Leishmania donovani.

Chromatin modifications affect several processes. In investigating the Leishmania donovani histone acetyltransferase HAT2, using in vitro biochemical assays and HAT2-heterozygous genomic knockout we found the constitutively nuclear HAT2 acetylated histone H4K10 in vitro and in vivo. HAT2 was essential. HAT2-depleted cells displayed growth and cell cycle defects, and poor survival in host cells. Real time PCR and DNA microarray analyses, as well as rescue experiments, revealed that downregulation of cyclins CYC4 and CYC9 were responsible for S phase and G2/M defects of HAT2-depleted cells respectively. Leishmania genes are arranged in unidirectional clusters, and clustered genes are coordinately transcribed as long polycistronic units, typically from divergent strand switch regions (dSSRs) which initiate transcription bidirectionally on opposite strands. In investigating the mechanism by which CYC4 and CYC9 expression levels are reduced in HAT2-depleted cells without other genes in their polycistronic transcription units being coordinately downregulated, we found using reporter assays that CYC4 and CYC9 have their own specific promoters. Chromatin immunoprecipitation assays with H4acetylK10 antibodies and real time PCR analyses of RNA suggested these gene-specific promoters were activated in cell cycle-dependent manner. Nuclear run-on analyses confirmed that CYC4 and CYC9 were transcriptionally activated from their own promoters at specific cell cycle stages. Thus, there are two tiers of gene regulation. Transcription of polycistronic units primarily initiates at dSSRs, and this most likely occurs constitutively. A subset of genes have their own promoters, at least some of which are activated in a cell-cycle dependent manner. This second tier of regulation is more sensitive to H4K10 acetylation levels, resulting in downregulation of expression in HAT2-depleted cells. This report presents the first data pointing to cell cycle-specific activation of promoters in trypanosomatids, thus uncovering new facets of gene regulation in this parasite family.

Histone acetyltransferase HAT4 modulates navigation across G2/M and re-entry into G1 in Leishmania donovani.

Histone acetyltransferases impact multiple processes. This study investigates the role of histone acetyltransferase HAT4 in Leishmania donovani. Though HAT4 was dispensable for survival, its elimination decreased cell viability and caused cell cycle defects, with HAT4-nulls experiencing an unusually long G2/M. Survival of HAT4-nulls in macrophages was also substantially compromised. DNA microarray analysis revealed that HAT4 modestly regulated the expression of only a select number of genes, thus not being a major modulator of global gene expression. Significantly, cdc20 was among the downregulated genes. To ascertain if decreased expression of cdc20 was responsible for HAT4-null growth and cell cycle defects we expressed LdCdc20 ectopically in HAT4-nulls. We found this to alleviate the aberrant growth and cell cycle progression patterns displayed by HAT4-nulls, with cells navigating G2/M phase and re-entering G1 phase smoothly. HAT4-nulls expressing LdCdc20 ectopically showed survival rates comparable to wild type within macrophages, suggesting that G2/M defects were responsible for poor survival of HAT4-nulls within host cells also. These are the first data analyzing the in vivo functional role of HAT4 in any trypanosomatid. Our results directly demonstrate for the first time a role for Cdc20 in regulating trypanosomatid G2/M events, opening avenues for further research in this area.

Evaluation of potential flavonoid inhibitors of glyoxalase-I based on virtual screening and in vitro studies.

Glyoxalase-I (GLO-I) is a component of the ubiquitous detoxification system involved in the conversion of methylglyoxal (MG) to d-lactate in the glycolytic pathway. MG toxicity arises from its ability to form advanced glycation end products. GLO-I has been reported to be frequently overexpressed in various types of cancer cells. In this study, we performed structure-based virtual screening of focused flavonoids commercial library to identify potential and specific inhibitors of GLO-I. The compounds were ranked based on Glide extra precision docking score and five hits (curcumin, quercetin, morin, naringin and silibinin) were selected on the basis of their interaction with active site amino acid residues of GLO-I. Mixed mode QM/MM calculation was performed on the top-scoring hit to ascertain the role of zinc ion in ligand binding. In addition, the identified hits were subjected to MM/GBSA binding energy prediction, ADME prediction and similarity studies. The hits were tested in vitro for cell viability, and GLO-I inhibition. Naringin (ST072162) was found to be most potent inhibitor of GLO-I among the identified hits with highest glide XP dock score of -14.906. These findings suggest that naringin could be a new scaffold for designing inhibitors against GLO-I with potential application as anticancer agents.