Search

Parkinson's disease is characterized by the presence of insoluble and neurotoxic aggregates (amyloid fibrils) of an intrinsically disordered protein α-synuclein. In this study we have examined the effects of four naturally occurring polyphenols in combination with β-cyclodextrin (β-CD) on the aggregation of α-synuclein in the presence of macromolecular crowding agents. Our results reveal that even at sub-stoichiometric concentrations of the individual components, the polyphenol-β-CD combination(s) not only inhibited the aggregation of the proteins but was also effective in disaggregating preformed fibrils. Curcumin was found to be the most efficient, followed by baicalein with (-)-epigallocatechin gallate and resveratrol coming in next, the latter two exhibiting very similar effects. Our results suggest that the efficiency of curcumin results from a balanced composition of the phenolic OH groups, benzene rings and flexibility. The latter ensures proper positioning of the functional groups to maximize the underlying interactions with both the monomeric form of α-synuclein and its aggregates. The uniqueness of β-CD was reinforced by the observation that none of the other cyclodextrin variants [α-CD and HP-β-CD] used was as effective, in spite of these possessing better water solubility. Moreover, the fact that the combinations remained effective under conditions of macromolecular crowding suggests that these have the potential to be developed into viable drug compositions in the near future. MTT assays on cell viability independently confirmed this hypothesis wherein these combinations (and the polyphenols alone too) appreciably impeded the toxicity of the prefibrillar α-synuclein aggregates on the mouse neuroblastoma cell lines (N2a cells).

Amyloid assemblies are stabilized through inter-molecular H-bonding with initial structural organizations governed by extensive hydrophobic and π-stacking interactions. Apparently, the structural integrity and stability of DNA duplexes are also governed by a cooperative balance of similar interactions. Structural perturbations in both amyloids and DNA by planar molecules or intercalators essentially rely on their ability to interfere with this balance. However, poor information on amyloid interference mechanisms by intercalators has subjected researchers to undertake random trials with such anti-amyloidogenic agents. Here, we employed four different classes of DNA intercalators to investigate if their non-native, hetero-aromatic associations could modulate the amyloid aggregation pathway. We utilized micro-second scale MD simulations using the steric-zipper structure of the diabetes associated amylin fragment to identify such associations and their plausible role in subjugating higher order assemblies. The simulation estimates were experimentally validated and extended to other disease-associated amyloid systems including gelsolin, prion and lysozyme. We find that the intercalators essentially stabilize monomeric and prefibrillar assemblies, reducing their ability to transform into structured supramolecular structures. Our results conclusively establish the dominant role of aromatic-associations in diverting the course of the amyloid assembly process at the expense of stabilizing H-bonding networks. Overall this report presents comprehensive experimental and theoretical insights on the regulation of amyloidogenesis by aromatic planar moieties.

Cellular prion protein (PrP) misfolds into an aberrant and infectious scrapie form (PrPSc) that lead to fatal transmissible spongiform encephalopathies (TSEs). Association of prions with G-quadruplex (GQ) forming nucleic acid motifs has been reported, but implications of these interactions remain elusive. Herein, we show that the promoter region of the human prion gene (PRNP) contains two putative GQ motifs (Q1 and Q2) that assume stable, hybrid, intra-molecular quadruplex structures and bind with high affinity to PrP. Here, we investigate the ability of PrP to bind to the quadruplexes in its own promoter. We used a battery of techniques including SPR, NMR, CD, MD simulations and cell culture-based reporter assays. Our results show that PrP auto-regulates its expression by binding and resolving the GQs present in its own promoter. Furthermore, we map this resolvase-like activity to the N-terminal region (residues 23-89) of PrP. Our findings highlight a positive transcriptional-translational feedback regulation of the PRNP gene by PrP through dynamic unwinding of GQs in its promoter. Taken together, our results shed light on a yet unknown mechanism of regulation of the PRNP gene. This work provides the necessary framework for a plethora of studies on understanding the regulation of PrP levels and its implications in prion pathogenesis.

Background Postoperative suction drains are used after total knee arthroplasty to avoid intra-articular hematoma formation although they can increase blood loss due to a negative suction effect. The use of tranexamic acid to reduce blood loss may nullify this. The aim of this study was to compare outcomes in patients undergoing total knee arthroplasty with or without drains and to analyze whether the drain's diameter also has an impact. Methods This is a prospective randomized study of patients undergoing unilateral total knee arthroplasty performed by a single surgeon. The study population was divided into three groups (A, 10G drain; B, 12G drain; and C, no drain). Pain, blood loss, swelling, wound-related complications, functional outcomes and questionnaire-based outcomes were assessed postoperatively. Results Each group had 35 patients comparable in most demographic and pre- and intraoperative characteristics. During the first 6 hours postoperatively, opioid consumption was significantly higher when the drain was not used (p = 0.036). At 3 months postoperatively, new Knee Society Score (NKSS) was highest with the use of 12G drain (p = 0.018). However, NKSS at 1 year was comparable across the three groups. With the use of tranexamic acid, blood loss and incidence of soakage of dressing were unaffected by the presence or absence of a drain. The calf girth, suprapatellar girth, soakage of dressing and range of motion were comparable in all three groups. There was no incidence of surgical site infection or deep vein thrombosis. Conclusions Presence of a suction drain significantly reduces opioid consumption during the first 6 hours after total knee arthroplasty. Use of a drain made no difference to the functional outcome at 1 year postoperatively. With the use of tranexamic acid in total knee arthroplasty, the total blood loss and the requirement of blood transfusion were unaffected by the presence or absence of closed suction drainage or by the bore of the drain used. The clinical parameters such as swelling, range of motion, infection and deep vein thrombosis also remained the same.

Ulnar nerve compression at guyon’s canal is rare and very few cases have been reported in literature. It can be missed due to its rarity. Symptoms vary from pain and paresthesia to wasting and significant loss of muscle strength, with significant deformities of the hand. The diagnosis is made by detailed history and examination, electromyography, nerve conduction velocity test, ultrasound and magnetic resonance imaging. Early decompression of nerve is treatment of choice. Here we are presenting a case of compression of ulnar nerve in guyon’s canal due to ganglionic cyst.