Enhancement in the antibacterial activity of Rifaximin by delivery through gelatin nanoparticles.

OBJECTIVES: Bacterial infections are a noteworthy global health concern that necessitates the development of new strategies to enhance the potency and efficacy of antibiotics. Rifaximin (RFX), a broad-spectrum antibiotic, exhibits promising antibacterial activity against several bacterial strains. However, its insolubility and impermeability impede the exploitation of its full potential. The objective of the current study is to overcome the inherent caveats of RFX to exploit its maximum potential. SIGNIFICANCE: The exploitation of the full potential of antibiotics is necessary for reduction in their dosage and to minimize antibiotic pollution. This is a preliminary study aiming for maximum utilization of RFX at the target site and reduction in its release in unmetabolized form. METHODS: Gelatin is a biopolymer that has gained significant attention for biomedical applications owing to its inherent biocompatibility and biodegradability. In this study, bovine gelatin nanoparticles (BGNPs) were fabricated by the self-assembly method for their application as a carrier of RFX to enhance its antibacterial activity. The study employs a comprehensive range of experimental techniques to characterize the fabricated BGNPs such as DLS, Zeta Potential, FT-IR, AFM, SEM-EDX, and UV-Vis spectrophotometry. RESULTS: The average size of the fabricated BGNPs was 100 nm with a zeta potential value of -15.3 mV. The loading of RFX on BGNPs rendered an increase in its size to 136 nm with a zeta potential value of -16 mV. In-vitro assays and microscopic analyses were conducted to compare the antibacterial efficacy of RFX and RFX@BGNPs. An excellent loading capacity followed by sustained release of RFX from RFX@BGNPs rendered a significant enhancement in its pharmaceutical efficacy. The release of RFX from RFX@BGNPs followed the Higuchi and Korsmeyer-Peppas models. The antibacterial efficacy of RFX against Staphylococcus aureus has doubled by delivery through RFX@BGNPs, assessed by inhibitory and biofilm inhibitory assays. The enhancement in the antibacterial efficiency was further endorsed by SEM and microscopic imaging of the control and treated bacterial colonies. CONCLUSION: The study demonstrates an enhancement in the antimicrobial efficacy of RFX by its delivery in the form of RFX@BGNPs to exploit its full potential for practical applications.

Acidotic and hypoxic tumor microenvironment induces changes to histone acetylation and methylation in oral squamous cell carcinoma.

Hypoxia and acidosis are ubiquitous hallmarks of the tumor microenvironment (TME), and in most solid cancers they have been linked to rewired cancer cell metabolism. These TME stresses are linked to changes in histone post-translational modifications (PTMs) such as methylation and acetylation, which lead to tumorigenesis and drug resistance. Hypoxic and acidotic TME cause changes in histone PTMs by impacting the activities of histone-modifying enzymes. These alterations are yet to be extensively explored in oral squamous cell carcinoma (OSCC), one of the most prevalent cancers in developing countries. Hypoxic, acidotic, and hypoxia with acidotic TME affecting histone acetylation and methylation in the CAL27 OSCC cell line was studied using LC-MS-based proteomics. The study identified several well-known histone marks, in the context of their functionality in gene regulation, such as H2AK9Ac, H3K36me3, and H4K16Ac. The results provide insights into the histone acetylation and methylation associated with hypoxic and acidotic TME, causing changes in their level in a position-dependent manner in the OSCC cell line. Hypoxia and acidosis, separately and in combination, cause differential impacts on histone methylation and acetylation in OSCC. The work will help uncover tumor cell adaptation to these stress stimuli in connection with histone crosstalk events.

PX-12 synergistically enhances the therapeutic efficacy of vorinostat under hypoxic tumor microenvironment in oral squamous cell carcinoma in vitro.

Hypoxia is a characteristic feature of solid tumors, including oral squamous cell carcinoma (OSCC), which causes therapeutic resistance. The hypoxia-inducible factor 1-alpha (HIF-1α) is a key regulator of hypoxic tumor microenvironment (TME) and a promising therapeutic target against solid tumors. Among other HIF-1α inhibitors, vorinostat (suberoylanilide hydroxamic acid, SAHA) is a histone deacetylase inhibitor (HDACi) targeting the stability of HIF-1α, and PX-12 (1-methylpropyl 2-imidazolyl disulfide) is a thioredoxin-1 (Trx-1) inhibitor preventing accumulation of HIF-1α. HDACis are effective against cancers; however, they are accompanied by several side effects along with an emerging resistance against it. This can be overcome by using HDACi in a combination regimen with Trx-1 inhibitor, as their inhibitory mechanisms are interconnected. HDACis inhibit Trx-1, leading to an increase in the production of reactive oxygen species (ROS) and inducing apoptosis in cancer cells; thus, the efficacy of HDACi can be elevated by using a Trx-1 inhibitor. In this study, we have tested the EC50 (half maximal effective concentration) doses of vorinostat and PX-12 on CAL-27 (an OSCC cell line) under both normoxic and hypoxic conditions. The combined EC50 dose of vorinostat and PX-12 is significantly reduced under hypoxia, and the interaction of PX-12 with vorinostat was evaluated by combination index (CI). An additive interaction between vorinostat and PX-12 was observed in normoxia, while a synergistic interaction was observed under hypoxia. This study provides the first evidence for vorinostat and PX-12 synergism under hypoxic TME, at the same time highlighting the therapeutically effective combination of vorinostat and PX-12 against OSCC in vitro.