Parkin cooperates with GDNF/RET signaling to prevent dopaminergic neuron degeneration

Parkin and the glial cell line–derived neurotrophic factor (GDNF) receptor RET have both been independently linked to the dopaminergic neuron degeneration that underlies Parkinson’s disease (PD). In the present study, we demonstrate that there is genetic crosstalk between parkin and the receptor tyrosine kinase RET in two different mouse models of PD. Mice lacking both parkin and RET exhibited accelerated dopaminergic cell and axonal loss compared with parkin-deficient animals, which showed none, and RET-deficient mice, in which we found moderate degeneration. Transgenic expression of parkin protected the dopaminergic systems of aged RET-deficient mice. Downregulation of either parkin or RET in neuronal cells impaired mitochondrial function and morphology. Parkin expression restored mitochondrial function in GDNF/RET-deficient cells, while GDNF stimulation rescued mitochondrial defects in parkin-deficient cells. In both cases, improved mitochondrial function was the result of activation of the prosurvival NF-κB pathway, which was mediated by RET through the phosphoinositide-3-kinase (PI3K) pathway. Taken together, these observations indicate that parkin and the RET signaling cascade converge to control mitochondrial integrity and thereby properly maintain substantia nigra pars compacta dopaminergic neurons and their innervation in the striatum. The demonstration of crosstalk between parkin and RET highlights the interplay in the protein network that is altered in PD and suggests potential therapeutic targets and strategies to treat PD.     

Metformin and Diabetic Kidney Disease: A Mini-Review on Recent Findings

Metformin, an oral anti-diabetic agent in the biguanide class is a widely prescribed drug to treat high blood glucose in patients with type 2 diabetes mellitus. Metformin has three different roles, including blood glucose regulatory effect, protection of kidney tubular cell by acting as an effective antioxidant and finally ameliorative effect on diabetic kidney disease through saving the podocytes. Therefore, diabetic patients may benefit from all of these three distinct ameliorative effects.Key Words: Metformin, Kidney Disease, Diabetes, Anti-diabetic Agents     

Deciphering the canonical blockade of activated Hageman factor (FXIIa) by benzamidine in the coagulation cascade: A thorough dynamical perspective

The experimental inhibitory potency of benzamidine (BEN) paved way for further design and development of inhibitors that target β‐FXIIa. Structural dynamics of the loops and catalytic residues that encompass the binding pocket of β‐FXIIa and all serine proteases are crucial to their overall activity. Employing molecular dynamics and post‐MD analysis, this study sorts to unravel the structural and molecular events that accompany the inhibitory activity of BEN on human β‐FXIIa upon selective non‐covalent binding. Analysis of conformational dynamics of crucial loops revealed prominent alterations of the original conformational posture of FXIIa, evidenced by increased flexibility, decreased compactness, and an increased exposure to solvent upon binding of BEN, which could have in turn interfered with the essential roles of these loops in enhancing their procoagulation interactions with biological substrates and cofactors, altogether resulting in the consequential inactivation of FXIIa. A sustained interaction of the catalytic triad residues and key residues of the autolysis loop impeded their roles in catalysis which equally enhanced the inhibitory potency of BEN toward β‐FXIIa evidenced by a favorable binding. Findings provide essential structural and molecular insights that could facilitate the structure‐based design of novel antithrombotic compounds with enhanced inhibitory activities and low therapeutic risk.     

Improved Strength and Toughness of Carbon Woven Fabric Composites with Functionalized MWCNTs

This investigation examines the role of carboxyl functionalized multi-walled carbon nanotubes (COOH-MWCNTs) in the on- and off-axis flexure and the shear responses of thin carbon woven fabric composite plates. The chemically functionalized COOH-MWCNTs were used to fabricate epoxy nanocomposites and, subsequently, carbon woven fabric plates to be tested on flexure and shear. In addition to the neat epoxy, three loadings of COOH-MWCNTs were examined: 0.5 wt%, 1.0 wt% and 1.5 wt% of epoxy. While no significant statistical difference in the flexure response of the on-axis specimens was observed, significant increases in the flexure strength, modulus and toughness of the off-axis specimens were observed. The average increase in flexure strength and flexure modulus with the addition of 1.5 wt% COOH-MWCNTs improved by 28% and 19%, respectively. Finite element modeling is used to demonstrate fiber domination in on-axis flexure behavior and matrix domination in off-axis flexure behavior. Furthermore, the 1.5 wt% COOH-MWCNTs increased the toughness of carbon woven composites tested on shear by 33%. Microstructural investigation using Fourier Transform Infrared Spectroscopy (FTIR) proves the existence of chemical bonds between the COOH-MWCNTs and the epoxy matrix.     

Discovery and antiproliferative evaluation of new quinoxalines as potential DNA intercalators and topoisomerase II inhibitors

In continuation of our previous work on the design and synthesis of topoisomerase II (Topo II) inhibitors and DNA intercalators, a new series of quinoxaline derivatives were designed and synthesized. The synthesized compounds were evaluated for their cytotoxic activities against a panel of three cancer cell lines (Hep G‐2, Hep‐2, and Caco‐2). Compounds 18b, 19b, 23, 25b , and 26 showed strong potencies against all tested cell lines with IC₅₀ values ranging from 0.26 ± 0.1 to 2.91 ± 0.1 µM, comparable with those of doxorubicin (IC₅₀ values ranging from 0.65 ± 0.1 to 0.81 ± 0.1 µM). The most active compounds were further evaluated for their Topo II inhibitory activities and DNA intercalating affinities. Compounds 19b and 19c exhibited high activities against Topo II (IC₅₀ = 0.97 ± 0.1 and 1.10 ± 0.1 µM, respectively) and bound the DNA at concentrations of 43.51 ± 2.0 and 49.11 ± 1.8 µM, respectively, whereas compound 28b exhibited a significant affinity to bind the DNA with an IC₅₀ value of 37.06 ± 1.8 µM. Moreover, apoptosis and cell‐cycle tests of the most promising compound 19b were carried out. It was found that 19b can significantly induce apoptosis in Hep G‐2 cells. It has revealed cell‐cycle arrest at the G2/M phase. Moreover, compound 19b downregulated the Bcl‐2 levels, indicating its potential to enhance apoptosis. Furthermore, molecular docking studies were carried out against the DNA–Topo II complex to examine the binding patterns of the synthesized compounds.     

Can acetaminophen/dimethyl sulfoxide formulation prevent accidental and intentional acetaminophen hepatotoxicity?

An overdose of acetaminophen (APAP) causes liver injury in experimental animals and humans. The activation step (formation of reactive metabolite, N-acetyl-p-benzoquinone imine by cytochrome P450 system) and the consequent downstream pathway of oxidative stress, nitrosative stress, and inflammation play an important role in APAP-induced hepatotoxicity. Formulation of APAP with an inhibitor of the activation step would be ideal to prevent accidental and intentional APAP toxicity. Dimethyl sulfoxide (DMSO) is a common colorless, inexpensive solvent, and considered safe in human. We hypothesized that a less hepatotoxic APAP if co-formulated with DMSO. To test this hypothesis, C57BL/6 mice were given toxic dose of APAP (250 mg kg⁻¹, i.p.) mixed with different doses of DMSO (25, 50, 100, and 200 μl kg⁻¹). Six hours after APAP treatment, blood and lives were collected for analysis. In DMSO treated groups, there was dose-dependent decrease in markers of liver injury, alanine aminotransferase, and aspartate aminotransferase. Maximum protection was obtained with 200 μl DMSO kg⁻¹. DMSO was shown to inhibit the activation step by decreasing the rate of GSH depletion in vivo and inhibiting cytochrome P450 system in vitro. Also the levels of lipid peroxides, nitrate/nitrite, tumor necrosis factor-alpha, and interleukin 1β were decreased significantly. In conclusion, DMSO exerts its protective action by inhibiting the metabolic activation of APAP and thus alleviating the downstream, oxidative stress, nitrosative stress, and inflammation via indirect inhibition. Our findings suggest that replacing the current APAP with APAP/DMSO formulation could prevent accidental and intentional APAP toxicity.