Biology subjects

Venkateshvaran, A.

Publications and source records attributed to Venkateshvaran, A..

3 recordsLinked to original sources

bioRxiv2025

3D human skeletal muscle organoids reveal distinct effects of high-dose dihydronicotinamide riboside on muscle development

The evaluation of NAD+-boosting compounds in human skeletal muscle is hindered by limitations of traditional 2D cultures and animal models. Human-relevant, three-dimensional (3D) engineered skeletal muscle organoids offer a promising platform to assess the biological effects of metabolic modulation. Here we engineered 3D human skeletal muscle organoids to investigate the impact of dihydronicotinamide riboside (NRH), a potent NAD+ precursor. Sustained exposure to high NRH concentrations (500 {micro}M) enhanced early differentiation markers, including increased myotube fusion and fast-twitch fiber area, but concurrently induced structural defects such as disrupted sarcomeric organization, enlarged acetylcholine receptor clusters, and impaired acetylcholine-stimulated calcium signaling. These results reveal that excessive and sustained NAD+ elevation can uncouple rapid differentiation from proper maturation in muscle tissue. Our results highlight the importance of dose and duration optimization for NAD+-boosting compounds and establish 3D engineered muscle organoids as a valuable non-animal platform for mechanistic toxicology and preclinical safety assessment.

bioengineering↗

bioRxiv2025

Analysis of Intracellular Fatty Acid Metabolism in Senescent Cells using Raman Microscopy

Cellular senescence, a stable growth-arrested state induced by stress or chemotherapeutic agents, is accompanied by metabolic remodeling that supports the senescence-associated secretory phenotype (SASP). Among these pathways, lipid and arachidonic acid (AA) metabolism play central roles in maintaining and propagating the senescent state. Here, we used hyperspectral confocal Raman microscopy to visualize biochemical remodeling in MCF7 human breast adenocarcinoma cells undergoing doxorubicin-induced senescence. Raman spectral analysis and principal-component decomposition revealed time-dependent alterations in lipid-associated vibrational modes--particularly CH2 and C=C stretching--consistent with enhanced lipid accumulation and remodeling between days 10 and 15 after DNA-damage induction. PCA of lipid- rich compartments isolated using true component analysis also confirms progressive increases in triacylglycerol and unsaturated lipid signatures. Using deuterated arachidonic acid (AA-d) and COX-2 inhibition, we further demonstrated real-time intracellular AA metabolism by tracking C=C-D stretching peaks (2220-2254 cm-{superscript 1}) in the Raman-silent window. The ratio of these deuterium bands to CH2 stretching provided a label-free quantitative metric for COX2-dependent AA turnover in senescent cells. Together, these findings establish Raman hyperspectral imaging as a powerful, non-perturbative tool to map lipid and oxylipin metabolism during cellular senescence, offering new avenues to identify metabolic vulnerabilities in senescent tumor cells.

biochemistry↗

bioRxiv2023

C-terminal cysteines of HRas control Erk signaling and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) mediated inhibition of myoblast differentiation.

HRas is an important node that controls cellular signaling, proliferation, and differentiation. Mutants of HRas (e.g., the constitutively active HRas V12) can be oncogenic, and can also inhibit myoblast differentiation. The C-terminal cysteines of HRas (Cys181 and Cys184) serve as substrates for intra-cellular reversible palmitoylation and de-palmitoylation reactions, which control its subcellular distribution. The relationship between the C-terminal cysteines of HRas, its intracellular distribution, and its cellular activity has remained unclear. Understanding this relationship has important implications for targeting HRas in pathogenic states where it is activated. In this study, we show that a mutation in the C-terminal of HRas, C181S, is sufficient to cause increased levels of HRas V12 in the Golgi, decreased HRas V12-driven Akt and Erk signaling and reverse the ability of HRas V12 to inhibit myoblast differentiation. This demonstrates the importance of C-terminal cysteines in controlling HRas V12. It has been previously shown that Cys184 can also be irreversibly modified by an electrophilic prostaglandin lipid 15d-PGJ2. This lipid is released by senescent cells as a part of senescence-associated secretory phenotype (SASP). In this study, we show that 15d-PGJ2 is secreted by senescent myoblasts formed by treatment with Doxorubicin. We also show that 15d-PGJ2 causes decreased levels of HRas within Golgi, activates Erk signaling (but not Akt signaling), and inhibits differentiation of C2C12 myoblasts in an HRas Cys184-dependent fashion. Chemotherapeutics such as Doxorubicin drive senescence and loss of skeletal muscle homeostasis in cancer patients. This study suggests that targeting the senescence-derived synthesis of 15-PGJ2 might be a target to promote muscle homeostasis after chemotherapy.

cell biology↗