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Different small molecules and nanomaterials have been known as inhibitors of protein misfolding and subsequent fibrillation, which marks the initiation of various degenerative conditions. This work explores the effect of polyphenol-capped gold nanoparticles on the extent of human serum albumin fibrillation. Silymarin-capped (SAuNPs), quercetin-capped (QAuNPs) and gallic acid-capped gold nanoparticles (GAuNPs) were synthesized with a uniform size range and their relative antioxidant capacity was determined through DPPH assay. The fibrillation of HSA at 65 °C was inhibited by ∼15% in the presence of SAuNPs and the process was monitored through a combination of Thioflavin T fluorescence spectroscopy, circular dichroism spectroscopy and microscopic analysis. The inhibitory effect appeared much pronounced in the case of QAuNPs (∼67%) and GAuNPs (∼60%). Using SDS PAGE analysis, we demonstrated that the different inhibitory activity of SAuNPs, QAuNPs, and GAuNPs could be attributed to the antioxidant potential of the individual nanoparticles. Our work revealed that apart from protein–nanoparticle surface interactions, the antioxidant capacity has a role in determining the effectiveness of a protein fibrillation inhibitor. Cytotoxic analysis of protein–gold nanoparticle aggregates on HaCaT cell lines further confirmed that the nanoparticles were biosafe and can be considered as active therapeutics for translational use.

Tumor necrosis factor-α (TNF-α)-induced keratinocyte inflammation plays a key role in the pathogenesis of multiple inflammatory skin diseases. Here we investigated the anti-inflammatory effect of S-allyl cysteine (SAC) on TNF-α-induced HaCaT keratinocyte cells and the mechanism behind its anti-inflammatory potential. SAC was found to inhibit TNF-α-stimulated cytokine expression. Further, SAC was found to inhibit TNF-α-induced activation of p38, JNK and NF-κB pathways. Interestingly, SAC was found to differentially regulate ERK MAP kinase in cells. TNF-α-induced transient ERK activation and SAC treatment resulted in sustained ERK activation both in the presence and absence of TNF-α. Additionally, SAC failed to inhibit the TNF-α-induced expression of the pro-inflammatory cytokines TNF-α and IL-1β when cells were treated with the MEK inhibitor PD98059, suggesting that the anti-inflammatory effect of SAC is via sustained activation of the ERK pathway. Since ERK activation has been reported to negatively regulate NF-κB-driven gene expression and we find that SAC activates ERK and negatively regulates NF-κB, we investigated whether there existed any crosstalk between the ERK and the NF-κB pathways. NF-κB-dependent reporter assay, visualization of the nuclear translocation of NF-κB-p65 subunit and determination of the cellular levels of I-κB, the inhibitor of NF-κB, revealed that SAC inhibited TNF-α-induced NF-κB activation, and PD98059 treatment reversed this effect. These results collectively suggest that SAC inhibits TNF-α-induced inflammation in HaCaT cells via a combined effect entailing the inhibition of the p38 and the JNK pathways and NF-κB pathway via the sustained activation of ERK.

Biopolymer nanoparticles functionalized with targeting ligands serve as carriers for a wide range of therapeutic payloads to desired sites of the body. Upon introduction into the blood stream, the nanoparticles tend to bind with the plasma proteins in its immediate vicinity, forming a protein corona. In this work, we have investigated the effects of differently functionalized PLGA nanoparticles on the formation of protein corona. It was observed that nanoparticles of uniform size range adsorbed protein in varying amounts and the final hard corona differed structurally with respect to nanoparticle surface functionalization. A combination of fluorescence spectroscopy and FTIR studies revealed that the association of plasma proteins with PLGA nanoparticles during corona formation was intricately guided by the nanoparticle surface chemistry. Densitometric analysis through one dimensional gel electrophoresis further showed that the plasma proteins present in the hard corona were different for each case of surface functionalization. The aggregation of plasma protein during corona formation as studied through Thioflavin T fluorescence and circular dichorism spectroscopy was also found to significantly differ with each nanoparticle type. It is evident that surface chemistry of biopolymeric nanoparticles defines the final corona form in the physiological environment, and this study on detailed understanding of nanoparticle-protein corona would help to develop nanomedicines for clinical applications.

The anti-cancer activity of garlic mainly arises due to the presence of various organosulfur compounds including diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS). Herewith, we report a number of 4-substituted benzyl analogs of DADS and their selenium counterparts for a detailed structure-activity relationship towards their anti-proliferative activities in human breast cancer cell lines. Disulfide having 4-cyano group exhibited highest activity among all disulfides. In contrast, all diselenides exhibited very good anti-proliferative activities than DADS. Furthermore, unlike disulfides, diselenides were more selective towards cancer cells over normal cells. Some active compounds were further tested for their activities in some organ specific cell lines such as HepG2, PC-3 and HCT-116 to understand their efficacy. Elevated level of intracellular reactive oxygen species (ROS) by most of the benzyl diselenides reveals a possible mode of their action. Therefore, this study indicates that the anti-proliferative activity of DADS can be significantly enhanced upon suitable structural modifications.

Hydrogen peroxide (H2O2) mediated oxidative stress leading to hepatocyte apoptosis plays a pivotal role in the pathophysiology of several chronic liver diseases. This study demonstrates that S-allyl cysteine (SAC) renders cytoprotective effects on H2O2 induced oxidative damage and apoptosis in HepG2 cells. Cell viability assay showed that SAC protected HepG2 cells from H2O2 induced cytotoxicity. Further, SAC treatment dose dependently inhibited H2O2 induced apoptosis via decreasing the Bax/Bcl-2 ratio, restoring mitochondrial membrane potential (∆Ψm), inhibiting mitochondrial cytochrome c release, and inhibiting proteolytic cleavage of caspase-3. SAC protected cells from H2O2 induced oxidative damage by inhibiting reactive oxygen species accumulation and lipid peroxidation. The mechanism underlying the antiapoptotic and antioxidative role of SAC is the induction of the heme oxygenase-1 (HO-1) gene in an NF-E2-related factor-2 (Nrf-2) and Akt dependent manner. Specifically SAC was found to induce the phosphorylation of Akt and enhance the nuclear localization of Nrf-2 in cells. Our results were further confirmed by specific HO-1 gene knockdown studies which clearly demonstrated that HO-1 induction indeed played a key role in SAC mediated inhibition of apoptosis and ROS production in HepG2 cells, thus suggesting a hepatoprotective role of SAC in combating oxidative stress mediated liver diseases.