Biology subjects

Patel, A. K.

Publications and source records attributed to Patel, A. K..

5 recordsLinked to original sources

bioRxiv2026

Dynamic regulation of cystathionine gamma-lyase expression during normoxia, ischemia, and reperfusion in liver: interplay of transcription factors, microRNAs, and histone modifications

Cystathionine gamma-lyase (CTH), a key enzyme in hydrogen sulfide (H2S) biosynthesis, has been studied extensively in models of oxidative stress. Dysregulated CTH has been reported in cardiovascular disease, ischemia-reperfusion (I/R) injury, aging, and xenobiotic stress, where reactive oxygen species are central to pathology. Despite this, how CTH is regulated at the molecular level under basal, ischemic, and reperfusion conditions is largely unknown. We observed that CTH expression is dysregulated during ischemia and reperfusion in Huh7 hepatic cells, mouse liver, and human liver, and therefore systematically dissected its transcriptional, post-transcriptional, and epigenetic control. Promoter-deletion reporter assays identified the -275/+91 bp region as the core human CTH promoter. This region was predicted to harbour binding sites for Sp1, CREB, and NFY, which were confirmed through overexpression, knockdown or inhibition, and ChIP assays in Huh7 cells. Computational and experimental screening identified miR-150-5p and miR-510-5p as novel post-transcriptional regulators that bind directly to the CTH 3'-UTR. We also examined histone marks (H3K9ac, H3K9me3, H3K4me3, and H3K27me3) at the CTH promoter and found that H3K9ac, H3K4me3, and H3K27me3 correlate with CTH expression across basal, ischemic, and reperfusion conditions. Mechanistically, ischemia reduces Sp1 occupancy at the CTH promoter, raises miR-150-5p and miR-510-5p levels, lowers H3K9ac, collectively suppressing CTH. Reperfusion reverses this with greater Sp1 and CREB binding, lower miR-150-5p and miR-510-5p levels, and reduced H3K27me3, restoring CTH expression. Together, these findings reveal novel roles for Sp1, CREB, NFY, miR-150-5p, miR-510-5p, and histone modifications in the regulation of CTH during basal, ischemia and reperfusion conditions.

molecular biology↗

bioRxiv2024

TGFb-ANGPT2-Tie2 axis in cancer-associated fibroblasts reprograms oral cancer cells to embryonic-like cell state with predictive significance of poor prognosis

Myofibroblastic cancer-associated fibroblasts (CAFs) in tumor stroma is identified as poor-prognostic indicator in oral cancer; however, biological mechanisms are largely unexplored. Here, we discovered the role of autocrine or exogenous transforming growth factor beta (TGF{beta}) in inducing Tunica Interna Endothelial cell kinase 2 (Tie2) -signaling through histone deacetylase-mediated downregulation of Tie2-antagonist, Angiopoietin-2 in CAFs, responsible for induction and maintenance of myofibroblastic differentiation. To understand the influence of CAF-specific Tie2-signaling on cancer cell properties, we performed CAF-Cancer cell co-culture and its single-cell RNA sequencing (scRNA-Seq). Distinct clustering of CAFs suggested their transcriptional heterogeneity, driven by TGF{beta}-Tie2 activation. Interestingly, CAF-specific Tie2-signaling was responsible to reprogram cancer cells, producing embryonic-like cell state with increased stemness and EMT signatures. Importantly, both the Tie2-specific gene expression signature as well as reprogrammed cancer cell specific gene expression modules were validated respectively in fibroblasts clusters and malignant cell clusters in two independent earlier reported scRNAseq studies of HNSCC tumors. Highlighting the translatability of our study, the gene expression signature derived from reprogrammed cancer cells showed significant association with poor prognosis in HNSCC patient of TCGA cohort. Pharmacological inhibition of Tie2-signaling in CAFs, significantly abrogated the tumor initiating ability of co-cultured oral cancer cell lines. Overall, combining our molecular and computational analysis, we may propose Tie2 as a novel factor responsible for CAF mediated cancer cell plasticity, associated with aggressive nature of oral cancer. TeaserTie2-signaling is activated in myofibroblasts which impacts the behaviour of malignant cells by inducing cancer cell plasticity to acquire stemness.

cancer biology↗

bioRxiv2023

Comparison of SARS-CoV-2 variants in primary human nasal cultures indicates Delta as most cytopathic and Omicron as fastest replicating

The SARS-CoV-2 pandemic was marked with emerging viral variants, some of which were designated as variants of concern (VOCs) due to selection and rapid circulation in the human population. Here we elucidate functional features of each VOC linked to variations in replication rate. Patient-derived primary nasal cultures grown at air-liquid-interface (ALI) were used to model upper-respiratory infection and human lung epithelial cell lines used to model lower-respiratory infection. All VOCs replicated to higher titers than the ancestral virus, suggesting a selection for replication efficiency. In primary nasal cultures, Omicron replicated to the highest titers at early time points, followed by Delta, paralleling comparative studies of population sampling. All SARS-CoV-2 viruses entered the cell primarily via a transmembrane serine protease 2 (TMPRSS2)-dependent pathway, and Omicron was more likely to use an endosomal route of entry. All VOCs activated and overcame dsRNA-induced cellular responses including interferon (IFN) signaling, oligoadenylate ribonuclease L degradation and protein kinase R activation. Among the VOCs, Omicron infection induced expression of the most IFN and IFN stimulated genes. Infections in nasal cultures resulted in cellular damage, including a compromise of cell-barrier integrity and loss of nasal cilia and ciliary beating function, especially during Delta infection. Overall, Omicron was optimized for replication in the upper-respiratory system and least-favorable in the lower-respiratory cell line; and Delta was the most cytopathic for both upper and lower respiratory cells. Our findings highlight the functional differences among VOCs at the cellular level and imply distinct mechanisms of pathogenesis in infected individuals. ImportanceComparative analysis of infections by SARS-CoV-2 ancestral virus and variants of concern including Alpha, Beta, Delta, and Omicron, indicated that variants were selected for efficiency in replication. In infections of patient-derived primary nasal cultures grown at air-liquid-interface to model upper-respiratory infection, Omicron reached highest titers at early time points, a finding that was confirmed by parallel population sampling studies. While all infections overcame dsRNA-mediated host responses, infections with Omicron induced the strongest interferon and interferon stimulated gene response. In both primary nasal cultures and lower-respiratory cell line infections by Delta were most damaging to the cells as indicated by syncytia formation, loss of cell barrier integrity and nasal ciliary function.

microbiology↗

bioRxiv2022

Quaternary Ammonium Salt-Modified Isabgol (Psyllium) Scaffold as an Antibacterial Dressing for Improved Wound Healing

Chronic wounds require suitable treatment and management strategies for proper healing. Among other causes, infection delays the healing of wounds and increases the risk of wound-related complications. Healing of chronic wounds requires an ingenious biomaterial that is biocompatible and anti-infective to achieve effective wound management. In this study, a wound dressing with inherent antibacterial and biocompatible properties was developed to assist the healing process. Natural polysaccharide Isabgol was chemically modified with Epoxy propyl trimethyl ammonium chloride to render antibacterial activity to the material. This is the first report of such chemical modification of this polymer for biomedical applications. The modified material was freeze-dried to obtain scaffolds. 13C NMR and FTIR analysis confirmed the modification of the Isabgol polymer chains with EPTMAC. The scaffold exhibits an organized porous structure that allows the exchange of gases and nutrients through the matrix, as confirmed by SEM analysis. The material possesses excellent swelling properties up to 17 times its initial weight that allows it to absorb wound exudates and maintain a moist environment at the wound site. The scaffold is biodegradable, and thermally and mechanically stable. The material is anti-infective and can prevent infections at the wound site, which is one of the major causes of delayed wound healing. The developed scaffolds have been proven to be biocompatible and suitable for use in blood contact applications. Finally, since Isabgol is a low-cost raw material, the quaternary ammonium-modified Isabgol scaffold can be an affordable wound dressing material.

bioengineering↗

bioRxiv2019

Biomolecular Contrast Agents for Optical Coherence Tomography

Optical coherence tomography (OCT) has gained wide adoption in biological and medical imaging due to its exceptional tissue penetration, 3D imaging speed and rich contrast. However, OCT plays a relatively small role in molecular and cellular imaging due to the lack of suitable biomolecular contrast agents. In particular, while the green fluorescent protein has provided revolutionary capabilities to fluorescence microscopy by connecting it to cellular functions such as gene expression, no equivalent reporter gene is currently available for OCT. Here we introduce gas vesicles, a unique class of naturally evolved gas-filled protein nanostructures, as the first genetically encodable OCT contrast agents. The differential refractive index of their gas compartments relative to surrounding aqueous tissue and their nanoscale motion enables gas vesicles to be detected by static and dynamic OCT at picomolar concentrations. Furthermore, the OCT contrast of gas vesicles can be selectively erased in situ with ultrasound, allowing unambiguous assignment of their location. In addition, gas vesicle clustering modulates their temporal signal, enabling the design of dynamic biosensors. We demonstrate the use of gas vesicles as reporter genes in bacterial colonies and as purified contrast agents in vivo in the mouse retina. Our results expand the utility of OCT as a unique photonic modality to image a wider variety of cellular and molecular processes.

bioengineering↗