Raised intracellular glucose concentrations reduce aggregation and cell death caused by mutant huntingtin exon 1 by decreasing mTOR phosphorylation and inducing autophagy

Huntington's disease is caused by a CAG trinucleotide repeat expansion that is translated into an abnormally long polyglutamine tract. This gain-of-function mutation is associated with huntingtin aggregation and cell death. Autophagy is an important clearance route for mutant huntingtin exon 1. While mammalian target of rapamycin (mTOR) is a key regulator of autophagy, the upstream modifiers of this process are poorly understood. Our previous expression profiling studies in HD cell models observed changes in four genes associated with glucose metabolism, including the GLUT1 glucose transporter. A role for intracellular glucose as a modulator for polyglutamine toxicity was suggested as cell death was reduced by GLUT1 overexpression. Here we show that the protective effect of GLUT1 is associated with decreased huntingtin exon 1 aggregation in cell models. Consistent with this result, we also observed reduced aggregation and enhanced clearance of mutant huntingtin when cells were cultured in raised glucose concentrations (8 g/l). These effects were mimicked by 8 g/l 2-deoxyglucose (2DOG) (transported, phosphorylated but not metabolized further), but not with 8 g/l 3-O-methyl glucose (transported but not metabolized further). Thus, this phenomenon is probably mediated by glucose-6-phosphate. Increased clearance of mutant huntingtin by raised glucose (8 g/l) and 2DOG correlated with increased autophagy and reduced phosphorylation of mTOR, S6K1 and Akt. Thus, raised intracellular glucose/glucose 6-phosphate levels reduce mutant huntingtin toxicity by increasing autophagy via mTOR and possibly Akt. As mTOR and Akt regulate a diversity of crucial cellular processes, our data also suggest a major new set of targets for intracellular glucose signalling.     

Antioxidant, cytotoxic and genotoxic evaluation of alcoholic extract of Polyalthia cerasoides (Roxb.) Bedd

Antioxidative potential of alcohol extract of Polyalthia cerasoides was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical, superoxide anion scavenging, and reducing power assays were performed. The extract showed significant reactive oxygen species (ROS) scavenging activity in all in vitro antioxidant assays and contained high level of total phenolic content. For in vivo genotoxic evaluation, Swiss albino mice were treated with alcohol extract at the concentration of 40mg/kg body weight. Frequency of aberration was compared with control. Both the sets did not showed genotoxic effect. Further the extract was subjected to cytotoxic study using 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphynyl tetrazolium bromide (MTT) assay, the extract confirmed to show moderate cytotoxicity against L929 cell line.     

Three-dimensional quantitative structure-activity relationship modeling of gamma-secretase inhibitors using molecular field analysis

Three-dimensional quantitative structure-activity relationship analysis of a set of 79 analogs of gamma-secretase inhibitors was performed by molecular field analysis with genetic partial least squares method to investigate the substitutional requirements to derive a predictive model and for the favorable receptor-drug interaction that may be used for the designing of a novel gamma-secretase inhibitors. The developed molecular field analysis model has a good fit, with r2 value of 0.952 and cross-validated coefficient, r2(cv), value of 0.931. Predictive ability of the developed model was further assessed using test set of 19 compounds and r2(pred) was found to be 0.665.     

Virtual screening of cathepsin k inhibitors using docking and pharmacophore models

Cathepsin K is a lysosomal cysteine protease that is highly and selectively expressed in osteoclasts, the cells which degrade bone during the continuous cycle of bone degradation and formation. Inhibition of cathepsin K represents a potential therapeutic approach for diseases characterized by excessive bone resorption such as osteoporosis. In order to elucidate the essential structural features for cathepsin K, a three-dimensional pharmacophore hypotheses were built on the basis of a set of known cathepsin K inhibitors selected from the literature using catalyst program. Several methods are used in validation of pharmacophore hypothesis were presented, and the fourth hypothesis (Hypo4) was considered to be the best pharmacophore hypothesis which has a correlation coefficient of 0.944 with training set and has high prediction of activity for a set of 30 test molecules with correlation of 0.909. The model (Hypo4) was then employed as 3D search query to screen the Maybridge database containing 59,000 compounds, to discover novel and highly potent ligands. For analyzing intermolecular interactions between protein and ligand, all the molecules were docked using Glide software. The result showed that the type and spatial location of chemical features encoded in the pharmacophore are in full agreement with the enzyme inhibitor interaction pattern identified from molecular docking.     

Soft tissue tuberculosis – An unusual presentation of a common disease

Tuberculosis (TB) has reached epidemic proportions in India with a myriad of clinical presentations. Extra pulmonary TB can present in a wide variety of clinical forms and its identification requires a high degree of clinical suspicion. Soft tissue infection by Mycobacteria is rare. The diagnosis is often not thought of owing to the rarity of this entity.     

Electrolyte imbalance after total joint arthroplasty: risk factors and impact on length of hospital stay

Background

Clinical as well as subclinical hyponatremia is frequently seen after orthopedic surgery. The study was aimed to determine the frequency and severity of hyponatremia in a cohort of total joint arthroplasty cases and identify the risk factors and their impact.

Methods

This is a retrospective observational study of 546 consecutive cases of total joint arthroplasty patients from a single institution. Only primary hip and knee replacements were included. The study was approved by the institutional review board. Preoperative and postoperative serum electrolytes were recorded till 45-day review. This was correlated with the age, gender, BMI, drug intake, and comorbidities.

Results

We identified 84.9% postsurgical hyponatremia in our cohort. Of these 80% were mild, 16% moderate and 4% severe. Preoperative hyponatremia was a consistent finding in most severe cases. Thaizides, ACE inhibitors, and longer surgeries like bilateral TKRs had more hyponatremia. Hospital stay was not impacted in this study for reasons discussed. There were no deaths in this series during the follow-up period, but two patients were rehospitalized.

Conclusion

Postsurgical hyponatremia occurs in up to 85% of primary hip and knee arthroplasty patients. The most consistent predictor of severe electrolyte disturbance postsurgery is preoperative hyponatremia. Older age, female gender, longer surgery, and drugs like thiazides and ACE inhibitors seemed contributory.

     

Development of a High-Performance Liquid Chromatographic Method for Determination of Letrozole in Wistar Rat Serum and its Application in Pharmacokinetic Studies

A fast, sensitive, and specific reversed-phase high-performance liquid chromatographic (RP–HPLC) method for the determination of letrozole in Wistar rat serum was developed. In this method, liquid–liquid extraction of letrozole was achieved using diethyl ether as the extracting solvent. The analysis was carried out on a reversed-phase C18 (250 mm × 4.6 mm, 5 μm) column with an isocratic mobile phase of methanol–water (70:30,v/v), at a flow rate of 1.0 mL min⁻¹. Detection was carried out at 239 nm with a UV–visible spectrophoto-metric detector. The method was shown to be selective and linear over the concentration range of 0.15–100 μg mL⁻¹. The intra-day and inter-day precision studies showed good reproducibility with coefficients of variation less than 11% for the analyte. The relative errors of intra– and inter–day accuracy were within −11.52 to −2.26%. The limit of quantification was evaluated to be 0.15 μg mL⁻¹. The method was successfully applied for the pharmacokinetic study of letrozole after oral administration of 10 mg kg⁻¹ of letrozole in six healthy Wistar rats.     

Quantum rods as nanocarriers of gene therapy

Both antisense oligonucleotides (ASODN) and small interfering RNA (siRNA) have enormous potential to selectively silence specific cancer-related genes and could therefore be developed to be important therapeutic anti-cancer drugs. The use of nanotechnology may allow for significant advancement of the therapeutic potential of ASODN and siRNA, due to improved pharmacokinetics, bio-distribution and tissue specific targeted therapy. In this mini-review, we have discussed the advantages of using a nanocarrier such as a multimodal quantum rod (QR) complexed with siRNA for gene delivery. Comparisons are made between ASODN and siRNA therapeutic efficacies in the context of cancer and the enormous application potential of nanotechnology in oncotherapy is discussed. We have shown that a QR-interleukin-8 (IL-8) siRNA nanoplex can effectively silence IL-8 gene expression in the PC-3 prostate cancer cells with no significant toxicity. Thus, nanocarriers such as QRs can help translate the potent effects of ASODN/siRNA into a clinically viable anti-cancer therapy. Drug delivery for cancer therapy, with the aid of nanotechnology is one of the major translational aspects of nanomedicine, and efficient delivery of chemotherapy drugs and gene therapy drugs or their co-delivery continue to be a major focus of nanomedicine research.