Biology subjects

Grumbach, I. M.

Publications and source records attributed to Grumbach, I. M..

6 recordsLinked to original sources

bioRxiv2026

Late radiation-induced brain injury is associated with functional cerebrovascular impairment without structural vessel loss in mice

Background: Radiation-induced brain injury (RIBI) is a major and often irreversible complication of cranial radiotherapy, affecting up to 90% of long-term survivors. Although cerebrovascular damage is a leading mechanistic hypothesis, whether chronic resting hypoperfusion occurs independently of structural vessel loss remains unknown. The aim of this study was to comprehensively characterize cerebrovascular, structural, and behavioral outcomes in a murine model of late RIBI to determine the primary drivers of vascular dysfunction. Methods: Adult C57BL/6 mice underwent 12 Gy whole-brain irradiation and were assessed one year later using laser speckle contrast imaging (LSCI), 7T MRI, immunohistochemistry, and behavioral testing. Results: Irradiated mice exhibited reduced pial flow velocity and flow area by LSCI, indicative of upstream cerebrovascular dysfunction, while bulk cortical tissue perfusion was preserved. This pial hypoperfusion was accompanied by cerebral atrophy, decreased T2* relaxation time and tissue iron deposition consistent with chronic microhemorrhage across multiple brain regions by MRI, blood-brain barrier disruption reflected by reduced ZO-1 and VE-cadherin expression, and increased anxiety-like behavior. Strikingly, capillary density, pericyte coverage, astrocyte endfeet, and NeuN-positive neuronal nuclei were all preserved. Conclusion: These findings demonstrate that functional vascular impairment - not structural vessel or neuronal loss - drives hypoperfusion and blood-brain barrier disruption in late RIBI. This dissociation between vascular dysfunction and rarefaction reframes the pathophysiology of RIBI and identifies endothelial dysfunction as a tractable therapeutic target for intervention.

neuroscience↗

bioRxiv2025

Long-Term Effects of Radiation Therapy on Cerebral Microvessel Proteome: A Six-Month Post-Exposure Analysis

BackgroundRadiation therapy (RT) treats primary and metastatic brain tumors, with about one million Americans surviving beyond six months post-treatment. However, up to 90% of survivors experience RT-induced cognitive impairment. Emerging evidence links cognitive decline to RT-induced endothelial dysfunction in brain microvessels, yet in vivo studies of endothelial injury remain limited. Investigating the molecular and cellular pathways connecting RT, endothelial dysfunction, and cognitive impairment is vital for developing targeted interventions. This study examines proteomic changes in cerebral microvessels following RT. MethodsWe conducted a comprehensive quantitative analysis comparing the proteome in cerebral microvessels from five control mice and five irradiated mice (12 Gy) 6 months after RT. Bioinformatics analyses included gene ontology (GO) enrichment, Mitocarta analysis, Ingenuity Pathway Analysis (IPA), and iPathwayGuide. Predictions from the analyses were validated by western blotting. ResultsOur data identified significant dysregulation of 414 proteins following RT, with 157 upregulated and 257 downregulated. Gene ontology analysis indicated that the majority of the dysregulated proteins were part of various metabolic pathways. Cross referencing with Mitocarta revealed a significant presence of mitochondrial proteins among the dysregulated proteins, indicating potential mitochondrial metabolic dysfunction. Further investigation with IPA analysis uncovered 76 enriched canonical pathways, 34 transcription regulators, 6 nuclear receptors, and 5 growth factors involved in RT-induced damage responses in cerebral microvessels. IPA canonical pathway analysis predicted mitochondrial dysfunction due to inhibition of various metabolic pathways in the irradiated group. Validation with western blotting confirmed the bioinformatics predictions from the proteomic dataset. ConclusionsOur data show significant proteomic changes in cerebral microvessels 6 months post-radiation, including oxidative phosphorylation, the TCA cycle, and glycolysis, suggesting metabolic mechanisms of RT-induced microvascular dysfunction.

bioinformatics↗

bioRxiv2024

MIRO1 controls energy production and proliferation of smooth muscle cells

BackgroundThe outer mitochondrial Rho GTPase 1, MIRO1, mediates mitochondrial motility within cells, but implications for vascular smooth muscle cell (VSMC) physiology and its roles in vascular diseases, such as neointima formation following vascular injury are widely unknown. MethodsCarotid ligation was performed in an in vivo model of selective Miro1 deletion in smooth muscle cells. VSMC proliferation during the cell cycle and molecular mechanisms of smooth muscle cell proliferation were explored in cultured aortic VSMCs by imaging mitochondrial positioning and cristae structure and assessing the effects on ATP production, metabolic function, and interactions with components of the electron transport chain (ETC). MIRO1 expression was also analyzed in human coronary arteries, and its function was assessed via knockdown in human coronary artery VSMCs. ResultsMIRO1 was highly expressed in VSMCs within human atherosclerotic plaques. MIRO1 facilitated VSMC proliferation and neointima formation by regulating mitochondrial positioning and PDGF-stimulated ATP production and respiration, critical for cell-cycle progression at G1/S. Deletion of Miro1 disrupted mitochondrial cristae structure, diminished ETC complex I activity, and impaired supercomplex formation. Notably, restoring MIRO1 function with expression of wild type MIRO1 recovered proliferation and ATP production and respiration, whereas a mutant lacking EF hands, which are essential for mitochondrial motility, only partially rescued these effects. MIRO1 knockdown in human coronary artery VSMCs confirmed its pivotal role in mitochondrial function and VSMC proliferation. ConclusionsThis study highlights two key mechanisms by which MIRO1 regulates VSMC proliferation. First, it maintains ATP synthesis by preserving mitochondrial cristae integrity. Second, its Ca2+-dependent EF hands enable ATP-dependent mitochondrial positioning. By linking mitochondrial motility and energy production to VSMC physiology, these findings position MIRO1 as a critical regulator of vascular remodeling and a potential target for therapeutic interventions.

cell biology↗

bioRxiv2023

Short-term statin treatment reduces, and long-term statin treatment abolishes chronic vascular injury by radiation therapy

BackgroundThe incidental use of statins during radiation therapy has been associated with a reduced long-term risk of developing atherosclerotic cardiovascular disease. ObjectivesDetermine if irradiation causes chronic vascular injury and whether short-term administration of statins during and after irradiation is sufficient to prevent chronic injury compared to long-term administration. MethodsC57Bl/6 mice were pretreated with pravastatin for 72 hours and then exposed to 12 Gy x-ray head-and-neck irradiation. Subsequently, they received pravastatin either for one additional day or for one year. Carotid arteries were tested for vascular reactivity and altered gene expression one year after irradiation. ResultsTreatment with pravastatin for 24 hours reduced the loss of endothelium-dependent vasorelaxation and protected against enhanced vasoconstriction after IR. It reduced the expression of some markers associated with inflammation and oxidative stress and modulated that of subunits of the voltage and Ca2+ activated K+ (BK) channel in the carotid artery one year after irradiation. Treatment with pravastatin for one year completely reversed the changes caused by irradiation. ConclusionsIn mice, short-term administration of pravastatin is sufficient to reduce chronic vascular injury after irradiation. Long-term administration eliminates the effects of irradiation. These findings suggest that a prospective treatment strategy involving statins could be effective in patients undergoing radiation therapy. The optimal duration of treatment in humans has yet to be determined.

pathology↗

bioRxiv2023

The mitochondrial regulation of smooth muscle cell proliferation in type 2 diabetes

BackgroundType 2 diabetes (T2D) is associated with a strongly increased risk for restenosis after angioplasty driven by proliferation of vascular smooth muscle cells (VSMCs). Here, we sought to determine whether and how mitochondrial dysfunction in T2D drives VSMC proliferation with a focus on ROS and intracellular [Ca2+] that both drive cell proliferation, occur in T2D and are regulated by mitochondrial activity. MethodsUsing a diet-induced mouse model of T2D, the inhibition of the mitochondrial Ca2+/calmodulin-dependent kinase II (mtCaMKII), a regulator of Ca2+ entry via the mitochondrial Ca2+ uniporter selectively in VSMCs, we performed in vivo phenotyping after mechanical injury and established the mechanisms of excessive proliferation in cultured VSMCs. ResultsIn T2D, the inhibition of mtCaMKII reduced both neointima formation after mechanical injury and the proliferation of cultured VSMCs. VSMCs from T2D mice displayed accelerated proliferation, reduced mitochondrial Ca2+ entry and membrane potential with elevated baseline [Ca2+]cyto compared to cells from normoglycemic mice. Accelerated proliferation after PDGF treatment was driven by activation of Erk1/2 and its upstream regulators. Hyperactivation of Erk1/2 was Ca2+-dependent rather than mitochondrial ROS-driven Ca2+-dependent and included the activation of CaMKII in the cytosol. The inhibition of mtCaMKII exaggerated the Ca2+ imbalance by lowering mitochondrial Ca2+ entry and increasing baseline [Ca2+]cyto, further enhancing baseline Erk1/2 activation. With inhibition of mtCaMKII, PDGF treatment had no additional effect on cell proliferation. Inhibition of activated CaMKII in the cytosol decreased excessive Erk1/2 activation and reduced VSMC proliferation. ConclusionsCollectively, our results provide evidence for the molecular mechanisms of enhanced VSMC proliferation after mechanical injury by mitochondrial Ca2+ entry in T2D.

molecular biology↗

bioRxiv2022

Knockout of Sorbs2 in Cardiomyocytes Leads to Dilated Cardiomyopathy in Mice

2.RationaleSorbs2 is a cardiomyocyte-enriched, cytoskeletal adaptor protein, and given some evidence for its dysregulated expression in failing hearts, there is growing interest in understanding its roles in cardiac biology and disease. While Sorbs2 global knockout mice display lethal cardiomyopathy with severe arrhythmias, the underlying mechanisms remain unclear, and whether this results from intrinsic loss of Sorbs2 in cardiomyocytes is unknown, as Sorbs2 is also well-expressed in the nervous system and vasculature. In addition, the potential relevance of Sorbs2 in human cardiomyopathy remains underexplored. ObjectiveTo characterize the effects and potential underlying mechanisms of cardiomyocyte- specific deletion of Sorbs2 on cardiac structure and function in mice, and to further examine Sorbs2 dysregulation in failing hearts and explore potential links between Sorbs2 genetic variations and human cardiovascular disease phenotypes. Methods and ResultsWe report that myocardial Sorbs2 expression is consistently upregulated in humans with ischemic and idiopathic cardiomyopathies, and in experimental animal models of heart failure (HF). We generated mice with cardiomyocyte-specific loss of Sorbs2 (Sorbs2-cKO) and found early atrial and ventricular conduction abnormalities, despite unaltered expression of primary action potential ion channels and gap junction proteins. At mid-life, Sorbs2-cKO mice exhibit impaired cardiac contractility with cardiomyofibers failing to maintain adequate mechanical tension. As a result, these mice develop progressive diastolic and systolic dysfunction, enlarged cardiac chambers, and die with congestive HF at approximately one year of age. Comprehensive survey of potential underlying mechanisms revealed that Sorbs2-cKO hearts exhibit defective microtubule polymerization and compensatory upregulation of structural proteins desmin, vinculin, and tubulins. Finally, consistent with our observations in mice, we identified suggestive links between Sorbs2 genetic variants and related human cardiac phenotypes, including conduction abnormalities, atrial enlargement, and dilated cardiomyopathy. ConclusionsOur studies show that Sorbs2 is essential for maintaining cytoskeletal structural integrity in cardiomyocytes likely through strengthening the interactions between microtubules and other structural proteins at crosslink sites. Overall, this study provides key insights into the critical role for Sorbs2 in cardiomyocytes and likely other cell types in maintaining normal cardiac structure and function and highlights its potential clinical relevance.

physiology↗