Biology subjects

Vellama, H.

Publications and source records attributed to Vellama, H..

3 recordsLinked to original sources

bioRxiv2026

Decoupling of CO2 and O2 fluxes reveals oxygen-independent decarboxylation in anoxic mammalian cells

Canonical understanding of cellular respiration holds that CO2 production tracks oxygen consumption, and mammalian cells deprived of oxygen are thought to rely on lactate fermentation, which yields no net CO2. Because standard respirometry infers CO2 flux either from oxygen consumption or from extracellular acidification rather than measuring it directly, a CO2 flux decoupled from oxygen would go undetected or be misattributed to glycolysis. Using direct measurement of CO2 and O2 fluxes from the gas phase in anoxic mammalian cells, we show that a substantial CO2 efflux persists after oxygen is fully removed. This anoxic flux scales linearly with normoxic CO2 and with cell mass, and exhibits a lower activation energy than normoxic respiration, suggesting a distinct rate-limiting chemistry. Pyruvate and -ketobutyrate increased the anoxic CO2 flux while lactate dehydrogenase inhibition abolished the pyruvate-induced increase, supporting a role for cytosolic NAD+ regeneration in oxygen-independent decarboxylation. 13C tracing identified a substantial glutamine-derived component, consistent with mitochondrial decarboxylation, and a smaller glucose-derived component associated with the cytosolic pentose phosphate pathway. Direct CO2 measurement thus reframes lactate dehydrogenase as an enabler of oxygen-independent decarboxylation.

biochemistry↗

bioRxiv2024

Pyruvate from bone marrow mesenchymal stem cells supports myeloma redox homeostasis and anabolism

Multiple myeloma is an incurable cancer of plasma cells that depends on the bone marrow for its survival. Despite its prevalence, the molecular mechanisms underlying this malignancy remain poorly understood. In this study, we aim to bridge this knowledge gap by elucidating the metabolic interplay between myeloma cells and bone marrow mesenchymal stem cells (BMMSCs). BMMSCs are crucial in supporting myeloma cell metabolism, contributing to their proliferation, survival, and resistance to chemotherapy. Through a combination of mathematical modelling and experimental co-cultures, we demonstrate that pyruvate - the end product of glycolysis - plays a key role in myeloma cell metabolism. Our findings reveal that myeloma cells predominantly rely on the uptake of pyruvate produced by neighbouring BMM-SCs via the plasma membrane proton-linked monocarboxylate transporters MCT-1 and MCT-2 encoded by the Slc16a1 and a2 genes, respectively. Furthermore, we show that pharmacological inhibition of the MCT-1/2, with AZD3965, triggers a cascade of compensatory metabolic responses, disrupting redox balance and significantly reducing the proliferation capacity of co-cultured myeloma cells.

cancer biology↗

bioRxiv2023

Inhibition of epigenetic and cell cycle-related targets in glioblastoma cell lines: onametostat reduces proliferation and viability in both normoxic and hypoxic conditions

The choice of targeted therapies for treatment of glioblastoma patients is currently limited, and most glioblastoma patients die from the disease recurrence. Thus, systematic studies in simplified model systems are required to pinpoint the choice of targets for further exploration in clinical settings. Here, we report screening of 5 compounds targeting epigenetic writers or erasers and 6 compounds targeting cell cycle-regulating protein kinases against 3 glioblastoma cell lines following incubation under normoxic or hypoxic conditions. The viability assay indicated that PRMT5 inhibitor onametostat was endowed with high potency under both normoxic and hypoxic conditions in both MGMT-positive and MGMT-negative cell lines. In U-251 MG and U-87 MG cells, onametostat also affected the spheroid formation at concentrations lower than the currently used chemotherapeutic drug lomustine. Furthermore, in T98-G cell line, treatment with onametostat led to dramatic changes in the transcriptome profile by inducing the cell cycle arrest, suppressing RNA splicing, and down-regulating several major glioblastoma cell survival pathways. In this way, we confirmed that inhibition of epigenetic targets might represent a viable strategy for glioblastoma treatment even in the case of decreased chemo- and radiation sensitivity, although further studies in clinically more relevant models are required.

cancer biology↗