Biology subjects

St. Croix, C.

Publications and source records attributed to St. Croix, C..

5 recordsLinked to original sources

bioRxiv2026

NITRITE INCREASES MITOFUSIN-1 LEVELS TO INHIBIT VASCULAR SMOOTH MUSCLE CELL PROLIFERATION AND PREVENT INTIMAL HYPERPLASIA

Vascular disease remains a leading cause of morbidity and mortality and is driven by maladaptive vascular remodeling following injury. Stent-induced vascular injury induces vascular smooth muscle cell (VSMC) phenotypic switching from a contractile to a proliferative state, resulting in intimal hyperplasia (IH), restenosis and compromised vessel function. Nitrite, an endogenous oxidation product of nitric oxide and a dietary constituent, attenuates IH after vascular injury; however, its underlying mechanisms remain incompletely understood. Nitrite is known to modulate mitochondrial structure and function, and dysregulated mitochondrial dynamics have independently been implicated in VSMC proliferation. We therefore hypothesized that nitrite attenuates IH by modulating mitochondrial dynamics to suppress VSMC proliferation. Using rat aortic smooth muscle cells (RASMCs), we demonstrate that nitrite treatment inhibits cell cycle progression and cell proliferation through upregulation of mitofusin-1 (Mfn1), a GTPase that catalyzes mitochondrial fusion. Mechanistically, nitrite increased Mfn1 protein levels by inhibiting Mfn1 proteasomal degradation. Mfn1 deletion resulted in enhanced proliferation, loss of contractile gene expression, and decreased expression of antioxidant enzymes including catalase and glutathione peroxidase. Restoration of cellular antioxidant capacity significantly attenuated proliferation and preserved contractile gene expression in Mfn1-deficient cells. Smooth muscle cell-specific Mfn1 knockout mice subjected to carotid artery ligation injury exhibited exacerbated IH compared to wildtype mice. Nitrite administration significantly decreased IH in wildtype mice but not Mfn1-deficient mice. These findings identify endogenous Mfn1 as a critical regulator of VSMC cell cycle progression and as an essential mediator of the vasoprotective effects of nitrite.

cell biology↗

bioRxiv2024

Germline loss diminishes somatic mitochondria but confers preservation of respiratory function during aging and hypothermia

Reproductive status influences metabolism and health across lifespan in diverse ways and mitochondrial function playing a critical role in mediating this relationship. Using the Caenorhabditis elegans germline ablation model, we investigated the impact of germline stem cell (GSC) loss on mitochondrial dynamics and respiratory function. Our results show that GSC loss reduces mitochondrial volume and respiratory function in young adulthood but preserves mitochondrial activity during aging and upon exposure to hypothermic stress, correlating with enhanced survival. We found that the transcription factor NHR-49/PPAR, but not DAF-16/FOXO3A, was essential for preserving mitochondrial function and hypothermia resistance in these long-lived mutants. Together, these findings reveal the impact of germline signals on somatic mitochondrial health and underscore the intricate relationship between reproductive fitness and organismal health.

genetics↗

bioRxiv2022

Carcinoma associated mesenchymal stem cells promote ovarian cancer metastasis by increasing tumor heterogeneity through direct mitochondrial transfer

Ovarian cancer is characterized by early, diffuse metastatic spread with most women presenting with extensive abdominal metastasis at the time of diagnosis. Prior work demonstrated carcinoma-associated mesenchymal stem cells (CA-MSCs) enhance ovarian cancer metastasis through a process of direct cellular interaction and formation of heterocellular CA-MSC and tumor cell complexes. In this study, we demonstrated that CA-MSCs enhance metastasis by increasing tumor cell heterogeneity through mitochondrial donation. We showed that CA-MSCs directly interacted with ovarian cancer cells via tunneling nanotubules (TNTs), and CA-MSCs used these TNTs to transfer live mitochondria to adjacent ovarian cancer cells. This mitochondrial donation preferentially occurred with ovarian cancer cells that had the lowest mitochondrial mass, as quantified using live, actively respiring mitochondrial labeling. These mito poor cancer cells demonstrated decreased proliferation, increased sensitivity to chemotherapy, and decreased oxidative phosphorylation compared to mito rich cancer cells. CA-MSCs rescued the phenotypes of mito poor cancer cells, restoring their proliferative capacity, increasing chemotherapy resistance, and increasing oxidative phosphorylation. We validated these findings in a fully autologous system using CA-MSCs and cancer cells derived from the same patient to prevent confounding effects of cellular response to foreign organelle/DNA. Using a knockdown of the mitochondrial motor protein, MIRO1, in CA-MSCs, we demonstrated that mitochondrial transfer is necessary for the CA-MSC-mediated rescue of mito poor cancer cells. Mitochondria of CA-MSC origin persisted in tumor cells over multiple passages. Importantly, CA-MSC mitochondrial donation occurred in vivo, significantly enhanced tumor cell heterogeneity and decreased survival in an orthotopic ovarian cancer mouse model. Collectively, this work identified CA-MSC mitochondrial transfer as a critical mediator of ovarian cancer cell survival, heterogeneity, and metastasis, and blocking CA-MSC mitochondrial transfer represents a unique therapeutic target in ovarian cancer.

cancer biology↗

bioRxiv2021

Cooperation between CYB5R3 and NOX4 via coenzyme Q mitigates endothelial inflammation

NADPH oxidase 4 (NOX4) regulates endothelial inflammation by producing reactive oxygen species. Since coenzyme Q (CoQ) mimics affect NOX4 activity, we hypothesize that cytochrome b5 reductase 3 (CYB5R3), a CoQ reductase abundant in vascular endothelial cells, modulates inflammatory activation. Mice lacking endothelial CYB5R3 (R3 KO), under lipopolysaccharides (LPS) challenge, showed exacerbated hypotension, decreased acetylcholine-induced vasodilation, and elevated vascular adhesion molecule 1 (Vcam-1) mRNA in aorta. In vitro, silencing Cyb5r3 enhanced LPS-induced VCAM-1 protein in a NOX4 dependent manner. APEX2- based electron microscopy and proximity biotinylation demonstrated CYB5R3s localization on the mitochondrial outer membrane and its interaction with NOX4, which was further confirmed by the proximity ligation assay. Notably, Cyb5r3 silenced HAECs had less total H2O2 but more mitochondrial O2*-. Using inactive or non-membrane bound active CYB5R3, we found CYB5R3 activity and membrane translocation were needed for optimal generation of H2O2 by NOX4. Lastly, CoQ deficient cells showed decreased NOX4-derived H2O2, indicating a requirement for endogenous CoQ in NOX4 activity. In conclusion, CYB5R3 mitigates endothelial inflammatory activation by assisting in NOX4-dependent H2O2 generation via CoQ. NOVELTY AND SIGNIFICANCEO_ST_ABSWhat Is Known?C_ST_ABSNADPH oxidase 4 (NOX4) reportedly produces primarily hydrogen peroxide (H2O2) and, to a lesser extent, superoxide (O2*-) and has been shown to have both beneficial and deleterious effects in the cardiovascular system. NOX4 activity can be affected by NAD(P)H quinone oxidoreductase 1 (NQO1), a CoQ reductase, and synthetic quinone compounds used to mimic CoQ. Cytochrome b5 reductase 3 (CYB5R3) is known to reduce CoQ and is highly expressed in endothelial cells. What New Information Does This Article Contribute?In vivo, the lack of endothelial CYB5R3 causes exacerbated lipopolysaccharides (LPS)-induced inflammatory signaling, endothelial dysfunction, and hypotension. Endothelial CYB5R3 mitigates inflammatory signaling by LPS and tumor necrosis factor (TNF-) in a NOX4 dependent manner. In endothelial cells, CYB5R3 and NOX4 reside in close proximity on the mitochondrial outer membrane. NOX4s ability to generate H2O2 depends on the membrane translocation and activity of CYB5R3 and the presence of endogenous CoQ. NONSTANDARD Abbreviations and Acronyms [Table 1] Protein names are abbreviated as capital letters (e.g., CYB5R3), while the corresponding gene names are annotated as in italic lower cases (e.g., Cyb5r3).

cell biology↗

bioRxiv2020

DIFFERENTIAL BIOENERGETICS IN ADULT RAT CARDIOMYOCYTES ISOLATED FROM THE RIGHT VERSUS LEFT VENTRICLE

The right and left ventricle of the heart have distinctly different developmental origins and are affected differently by similar pathological stimuli. Though it is well established that the heart relies almost entirely on mitochondrial function to sustain energy production, it remains unclear whether bioenergetics differ in the two ventricles. Herein, we define a novel methodology to optimize the isolation of intact cardiomyocytes from the right versus the left ventricle. We demonstrate that this segmental Langendorff-free methodology yields viable cardiomyocytes with intact mitochondrial function. Further, we compare bioenergetics in right versus left ventricle cardiomyocytes and show that cardiomyocytes from the right ventricle have a greater maximal capacity for respiration and enhanced glycolytic rate. This increase in respiration was concomitant with increased fatty acid oxidation and levels of fatty acid oxidation proteins, but no change in mitochondrial electron transport complex expression. These data validate a potentially powerful tool to evaluate differences in right and left ventricular function and advance the understanding of cardiac bioenergetic differences. These data will be discussed in the context of differential responses by the right versus ventricle in pathology.

cell biology↗