Exogenous substances like drugs, when absorbed, enter into the circulatory system and bind reversibly and extensively to human serum albumin (HSA). But transport of various drugs like a diuretic, furosemide (FUR), via albumin in uremia is seriously compromised due to accumulation of uremic toxins. The reason behind it is explored by investigating the binding mechanism of FUR to HSA. Isothermal titration calorimetry results show that FUR binds with HSA at high (Kb ∼ 10(4)) and low affinity (Kb ∼ 10(3)) sites whereas spectroscopic results predict binding at a single site (Kb ∼ 10(5)). Thermodynamic analysis shows that the HSA-FUR complex formation occurs via hydrogen bonds and hydrophobic interactions and undergoes slight structural changes, as evident by FTIR and far-UV CD. Further, the lifetime of HSA decreases only marginally and thus the magnitude of energy transfer efficiency is small, as obtained by time-resolved measurements. A displacement experiment predicts that the FUR binds mainly to site I but a new site having lower affinity is also observed, which shares some residues with site II as supported by molecular docking results. Results revealed that in uremia, FUR indirectly competes for Arg410, Lys414, and Ser489 with site II bound uremic toxins and directly competes for site I with site I bound uremic toxins.
Amyloid fibril formation by proteins leads to variety of degenerative disorders called amyloidosis. While these disorders are topic of extensive research, effective treatments are still unavailable. Thus in present study, two anti-tuberculosis drugs, i.e., pyrazinamide (PYZ) and D-cycloserine (DCS), also known for treatment for Alzheimer’s dementia, were checked for the anti-aggregation and anti-amyloidogenic ability on Aβ-42 peptide and hen egg white lysozyme. Results demonstrated that both drugs inhibit the heat induced aggregation; however, PYZ was more potent and decelerated the nucleation phase as observed from various spectroscopic and microscopic techniques. Furthermore, pre-formed amyloid fibrils incubated with these drugs also increased the PC12/SH-SY5Y cell viability as compare to the amyloid fibrils alone; however, the increase was more pronounced for PYZ as confirmed by MTT assay. Additionally, molecular docking study suggested that the greater inhibitory potential of PYZ as compare to DCS may be due to strong binding affinity and more occupancy of hydrophobic patches of HEWL, which is known to form the core of the protein fibrils.
A novel ionic tin(IV) iminodiacetic acid-piperazinediium conjugate (1) was designed and synthesized as a potential antitumor chemotherapeutic molecular entity and was thoroughly characterized by elemental analysis, FT-IR, 1 H, 13 C and 119 Sn NMR, ESI MS and single crystal X-ray crystallography. Complex 1 resulted from the proton transfer reaction between iminodiacetic acid (H 2 IDA) and piperazine (pipz), and its subsequent complexation with tin(IV) chloride salt. 1 crystallized in orthorhombic space group Ima2 and comprises of an anionic metallic unit, a piperazinediium cation and a chloride ion. In continuity of our previous strategy in search of robust metal-based antitumor drug entities exhibiting reduced systemic toxicity, we have carried out in vitro interaction studies of 1 with ct-DNA, tRNA and Topo I targets, to validate its chemotherapeutic potential. Complex 1 exhibited more avid binding propensity with RNA which was reflected by its higher K b and K values with RNA as compared to DNA.Topoisomerase inhibition activity of 1 was performed by gel electrophoresis which revealed significant inhibitory effect on the catalytic activity of the enzyme at 30 mM concentration. Molecular docking studies of the complex were carried out with DNA (PDB ID: 1BNA), RNA (PDB ID: 6TNA) and Topo I (PDB ID: ISC7) targets to ascertain the specific binding mode thereby substantiated the spectroscopic results.Cytotoxic studies were carried out on a panel of eight human cancer cell lines; U373MG, PC3, Hop62, HL60, HCT15, SK-OV-3, HeLa and MCF-7 by SRB assay which revealed significant regression specifically for HCT15, HOP62, MCF-7 and SK-OV-3 human cancer cell lines (GI 50 value < 10) as compared to the standard drug Adriamycin. Systemic toxicity of 1 was carried out by the estimation of oxidative stress biomarkers such as lipid peroxides (expressed as malondialdehyde; MDA) and reduced glutathione (GSH) levels in kidney and liver homogenates and the study was supported by the histopathologic examination of kidney and liver of female Wistar rats.
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