Biology subjects

Berk, B. C.

Publications and source records attributed to Berk, B. C..

9 recordsLinked to original sources

bioRxiv2026

Tirzepatide attenuates atherosclerosis through weight loss-independent anti-inflammatory mechanisms

BackgroundAtherosclerosis is a chronic inflammatory vascular disorder with persistent residual inflammation even after standard lipid-lowering therapy. Mounting evidence from bench to bedside suggests that diabetes and obesity accelerate atherosclerosis development. Tirzepatide (TZP), a dual Glucagon-Like Peptide-1 Receptor/Glucose-Dependent Insulinotropic Polypeptide Receptor (GLP-1R/GIPR) agonist approved for treating diabetes and obesity, has demonstrated proven cardiometabolic efficacy in large cardiovascular outcome trials. However, it remains largely uncertain whether TZP attenuates atherosclerosis independent of its anti-diabetic and anti-obese effects through direct actions on the vasculature. MethodsWe established atherosclerotic mouse models under diabetic, obese, and non-diabetic/non-obese conditions. Analysis of covariance (ANCOVA) and pair-feeding experiments were applied to experimentally decouple weight-dependent metabolic improvement from intrinsic vasculoprotection. Molecular and cell biological assays in human umbilical vein endothelial cells (HUVECs) and human aortic endothelial cells (HAECs) were performed to dissect the underlying signaling mechanisms. ResultsTZP markedly reduced aortic plaque burden and inflammation, restrained necrotic core enlargement, and improved plaque stability across all experimental mouse models. Both ANCOVA and pair-feeding experiments confirmed that these atheroprotective effects were independent of food intake and body weight loss. Furthermore, TZP attenuated systemic and vascular inflammation in Tumor Necrosis Factor- (TNF)-treated C57BL/6J mice, and this protection occurred without changes in body weight or blood glucose levels. Mechanistically, TZP directly targeted endothelial cells and activated the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA)/endothelial nitric oxide synthase (eNOS) pathway, increased eNOS phosphorylation and nitric oxide bioavailability, consequently downregulating the expression of the pro-inflammatory adhesion molecules Vascular Cell Adhesion Molecule-1 (VCAM-1) and Intercellular Adhesion Molecule-1 (ICAM-1). ConclusionsTZP arrests atherosclerosis progression through weight loss-independent anti-inflammatory mechanisms. These findings implicate TZP as a promising therapeutic drug for mitigating residual vascular inflammation in patients with atherosclerotic cardiovascular disease (ASCVD), irrespective of glycemic status or obesity. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LITirzepatide exerts direct anti-atherosclerotic effects in preclinical mouse models of atherosclerosis under diabetic, obese, and non-obese conditions. C_LIO_LITirzepatide directly targets endothelial GLP-1R/GIPR and downstream cAMP/PKA/eNOS signaling pathway to suppress NF-{kappa}B-driven vascular inflammation, thereby uncovering a previously unrecognized vasculoprotective mechanism underlying its cardiovascular benefits C_LI What Are the Clinical Implications?O_LITirzepatide exerts direct vascular protective effects independent of body weight reduction, suggesting that its cardiovascular benefits may extend beyond glycemic control and obesity management. C_LIO_LITirzepatide may represent a promising therapeutic drug for addressing residual vascular inflammation in ASCVD patients, including those without overt diabetes or obesity C_LI

physiology↗

bioRxiv2026

Endothelial cell RpL17-dependent translational control mediates intima-media thickening in response to disturbed flow

BackgroundCarotid intima-media thickening (IMT) is a major risk factor for cardiovascular disease (CVD). The large ribosomal subunit protein 17 (Rpl17) was recently reported as a CVD-associated gene; however, ribosomal mutations generally are not associated with vascular dysfunction. We have created a novel genetic model of decreased RpL17 in endothelial cells (EC) to determine how changes in endothelial ribosome expression cause IMT. MethodsEC-restricted RpL17 heterozygous mice (Cdh5-Cre; RpL17fl/wt, or Rpl17-Het), were generated and subjected to sham or partial carotid ligation (PCL) surgery of the left artery to induce acute disturbed (d)-flow in vivo. Carotids were harvested on day 14 for quantitative tissue immunostaining. Purified mouse and human EC in vitro were exposed to steady (s)-flow or d-flow using cone viscometry, and collected for flow cytometry, protein expression, electron microscopy, or purification of ribosomes. Human carotid samples from healthy and endarterectomy patients were used for tissue analysis. ResultsCarotids from RpL17-Het mice with PCL-induced d-flow showed increased IMT relative to RpL17-WT controls. In addition, RpL17 protein levels were decreased in regions of d-flow compared to s-flow. Increased levels of ER stress markers were observed by carotid immunostaining, as well as activation of the integrated stress response (ISR) in RpL17-Het EC. Analysis of mRNAs bound to polysomes vs. monosomes in EC-RpL17-Het revealed increased translational efficiency of key regulators of glycolysis, redox, inflammation, matrix, and endothelial-to-mesenchymal transition (EndMT). Metabolic profiling by Seahorse assay showed enhanced anaerobic glycolysis and decreased oxidative respiration in RpL17-Het EC, consistent with the translational efficiency data. Immunostaining of carotids identified upregulated EC inflammation and EndMT. ConclusionsOur data support RpL17 as a key mediator of EC phenotypic modulation that causes IMT in response to d-flow. We show a novel pathway for d-flow-mediated IMT: endoplasmic reticulum stress and activation of the ISR. These changes alter translational efficiency and reprogram EC cell cycle, metabolism, and redox state in the presence of d-flow to cause IMT, a precursor to cardiovascular pathology.

cell biology↗

bioRxiv2025

Re-evaluating the Impact of Biological Sex on Atherosclerosis in Apoe-/- and Ldlr-/- mice

BACKGROUNDThe progression of cardiovascular disease shows significant sexual dimorphism: although females generally develop the disease later in life, they exhibit a higher age-related incidence than males. Despite this clinical pattern, preclinical studies often overlook both sexes in their design, and existing research on sex-specific atherosclerosis in mice remains inconsistent. This study was designed to assess the influence of sex on atherosclerosis using two widely used atherosusceptible mouse models--Apoe-/- and Ldlr-/- mice. METHODSTo investigate the influence of sex on atherogenesis, we conducted a 20-week study using both male and female Apoe-/- and Ldlr-/- mice. The mice were fed an atherogenic ALMN diet (40% trans-fat, 2% cholesterol, 22% fructose) to promote plaque development. We performed comprehensive analyses of: (1) systemic metabolic parameters (lipid profile, glucose metabolism); (2) atherosclerotic burden (en face and aortic sinus plaque area); and (3) plaque composition (necrotic core size, collagen content, macrophage infiltration). RESULTSIn both models, male mice showed higher lipid levels, worse glucose tolerance, and reduced insulin sensitivity compared to females. Apoe-/- mice showed minimal sex differences in atherosclerosis with a trend toward increased plaque size in females. Plaque stability markers-- including collagen content, necrotic core size, and macrophage infiltration--did not differ significantly between sexes. In contrast, Ldlr-/- males exhibited greater en face plaque burden than females, yet plaque stability remained similar across sexes. CONCLUSIONComparative analysis of two widely used murine atherosclerosis models revealed genotype-dependent sexual dimorphism. Female Apoe-/- mice showed a non-significant trend toward larger plaque areas than males, whereas male Ldlr-/- mice developed significantly larger en face atherosclerotic plaques than females. By evaluating plaque area and composition across these models, our findings underscore the importance of including both sexes in atherosclerosis studies, in accordance with guidelines from the National Institutes of Health and the American Heart Association.

cell biology↗

bioRxiv2025

PDE10A Inhibition Reduces NLRP3 Activation and Pyroptosis in Sepsis and Nerve Injury

AbstractCell death and inflammation are key innate immune responses, but excessive activation can cause tissue damage. The NLRP3 inflammasome is a promising target for reducing inflammation and promoting recovery. Immunometabolism regulates NLRP3 responses in neurological and inflammatory diseases through cyclic nucleotide signaling. Targeting phosphodiesterases (PDEs), which hydrolyze cAMP and cGMP, offers a novel approach to mitigate inflammation. While 14 PDE inhibitors are FDA-approved, PDE10As role in NLRP3 inflammasome activation remains unclear. This study investigates the effects of PDE10A inhibition on inflammasome-driven inflammation using two PDE10A inhibitors, MP-10 and TP-10, in macrophage and animal models of sepsis and traumatic nerve injury. Our results show that PDE10A inhibition reduces inflammasome activation by preventing ASC speck formation and by lowering levels of cleaved caspase-1, gasdermin D, and IL-1{beta}, which are key mediators of pyroptosis. In the sepsis model, MP-10 significantly reduced inflammation, decreased plasma IL-1{beta}, alleviated thrombocytopenia, and improved organ damage markers. In the nerve injury model, PDE10A inhibition enhanced motor function recovery and reduced muscle atrophy-related gene expression. These findings suggest that PDE10A inhibition could be a promising therapeutic approach for inflammatory and neuromuscular injuries. Given MP-10s established safety in human trials, Phase 2 clinical studies for sepsis and nerve injury are highly promising.

immunology↗

bioRxiv2024

Spinal Cord Injury Enhances Lung Inflammation and Exacerbates Immune Response After Acute Lung Injury

The severity of spinal cord injury (SCI) is closely tied to pulmonary function, especially in cases of higher SCI levels. Despite this connection, the underlying pathological mechanisms in the lungs post-SCI are not well understood. Previous research has established a connection between disrupted sympathetic regulation and splenocyte apoptosis in high thoracic SCI, leading to pulmonary dysfunction. The aim of this study was to investigate whether mice with low-level SCI exhibit increased susceptibility to acute lung injury by eliciting systemic inflammatory responses that operate independently of the sympathetic nervous system. Here, we employed T9 contusion SCI and exposed mice to aerosolized lipopolysaccharide (LPS) to simulate lung inflammation associated with acute respiratory distress syndrome (ARDS). Twenty-four hours post-LPS exposure, lung tissues and bronchoalveolar lavage (BAL) fluid were analyzed. LPS markedly induced proinflammatory gene expression (SAA3, IRG1, NLRP3, IL-1beta, MCP-1) and cytokine release (IL-1beta, IL-6, MCP-1) in SCI mice compared to controls, indicating an exaggerated inflammatory response. Infiltration of Ly6G/C positive neutrophils and macrophages was significantly higher in SCI mice lungs post-LPS exposure. Interestingly, spleen size and weight did not differ between control and SCI mice, suggesting that T9 SCI alone does not cause spleen atrophy. Notably, bone-marrow-derived macrophages (BMDMs) from SCI mice exhibited hyper-responsiveness to LPS. This study demonstrated an increase in lung inflammation and immune responses subsequent to low-level T9 SCI, underscoring the widespread influence of systemic inflammation post-SCI, especially pronounced in specific organs like the lungs. KEY POINTSO_LISpinal cord injury leads to increased lung permeability following LPS inhalation. C_LIO_LISpinal cord injury amplifies cytokine release after exposure to LPS. C_LIO_LISpinal cord injury affects bone marrow-derived macrophages, showing heightened glycolytic activity and inflammatory conditions. C_LI

immunology↗

bioRxiv2024

Endothelial MICU1 protects against vascular inflammation and atherosclerosis by inhibiting mitochondrial calcium uptake

Atherosclerosis is triggered by endothelial activation and vascular inflammation, which is closely related to mitochondrial dysfunction. Mitochondrial calcium uptake 1 (MICU1), as the gatekeeper of mitochondrial Ca2+ homeostasis, is a critical player in mitochondrial function and implicated in a plethora of pathophysiological conditions. However, the role of MICU1 in the pathogenesis of vascular inflammation and atherosclerosis is unknown. We ask whether endothelial MICU1 can prevent vascular inflammation and atherosclerosis by maintaining mitochondrial homeostasis. We observed that vascular inflammation in response to LPS was aggravated in EC-specific Micu1 knockout mice (Micu1ECKO) and reduced in EC-specific Micu1 transgenic mice (Micu1ECTg). Furthermore, hypercholesterolemic Micu1ECKO mice also showed accelerated formation of atherosclerotic plaques, while Micu1ECTg mice protected against atherosclerosis. Mechanistically, MICU1 regulated mitochondrial Ca2+ influx, thereby reducing the expression of the mitochondrial deacetylase SIRT3 and the ensuing deacetylation of SOD2, leading to the burst of mitochondrial reactive oxygen species (mROS). Of clinical relevance, we identified decreased MICU1 level in endothelial layer of human atherosclerotic plaques, as well as in primary human aortic endothelial cells (HAECs) exposed to serum from patients with coronary artery diseases. Two-sample Wald ratio Mendelian randomization further revealed that increased expression of MICU1 was associated with decreased risk of coronary artery bypass grafting (CABG). Our findings unravel a critical and unrecognized role of MICU1 in preventing vascular inflammation and atherosclerosis by maintaining mitochondrial Ca2+ homeostasis.

molecular biology↗

bioRxiv2022

Pnpt1 mediates NLRP3 inflammasome activation by MAVS and metabolic reprogramming in macrophages

Polyribonucleotide nucleotidyltransferase 1 (Pnpt1) plays critical roles in mitochondrial homeostasis by controlling mitochondrial RNA (mt-RNA) processing, trafficking and degradation. Pnpt1 deficiency results in mitochondrial dysfunction that triggers a Type I interferon response, suggesting a role in inflammation. However, the role of Pnpt1 in inflammasome activation remains largely unknown. In this study, we generated myeloid-specific Pnpt1-knockout mice, and demonstrated that Pnpt1 depletion enhanced interleukin-1 beta (IL-1{beta}) and interleukin-18 (IL-18) secretion in mouse sepsis models. Using cultured peritoneal and bone marrow-derived macrophages we demonstrated that Pnpt1 regulated NLRP3 inflammasome dependent IL-1{beta} release in response to lipopolysaccharides (LPS), followed by nigericin, ATP or poly (I:C) treatment. Pnpt1 deficiency in macrophages increased glycolysis after LPS, and mt-reactive oxygen species (mt-ROS) after NLRP3 inflammasome activation. Pnpt1 activation of the inflammasome was dependent on both increased glycolysis and expression of the mitochondrial antiviral-signaling protein (MAVS), but not NF-{kappa}B signaling. Collectively, these data strengthen the concept that Pnpt1 is an important mediator of inflammation as shown by activation of the NLRP3 inflammasome in mouse sepsis and cultured macrophages.

immunology↗

bioRxiv2022

The lipid peroxidation product 4-hydroxynonenal inhibits NLRP3 inflammasome activation and macrophage pyroptosis

Pyroptosis is a form of cell death triggered by the innate immune system that has been implicated in the pathogenesis of sepsis and acute lung injury. At the cellular level, pyroptosis is characterized by cell swelling, membrane rupture, and release of inflammatory cytokines, such as IL-1{beta}. However, the role of endogenous lipids in pyroptosis remains underappreciated. We discovered that 4-hydroxynonenal (HNE), a major endogenous product of lipid peroxidation, inhibited pyroptosis and inflammasome activation. HNE at physiological concentrations (3 {micro}M) blocked nigericin and ATP-induced cell death, as well as secretion of IL-1{beta}, by mouse primary macrophages and human peripheral blood mononuclear cells. Treatment with HNE, or an increase of endogenous HNE by inhibiting glutathione peroxidase 4, reduced inflammasome activation in mouse models of acute lung injury and sepsis. Mechanistically, HNE inhibited the NLRP3 inflammasome activation independently of Nrf2 and NF-{kappa}B signaling, and had no effect on the AIM2 inflammasome. Furthermore, HNE directly bound to NLRP3 and inhibited its interaction with NEK7. Our findings identify HNE as a novel, endogenous inhibitor of the NLRP3 inflammasome.

immunology↗

bioRxiv2021

Cyclophilin A regulates protein phase separation and mitigates haematopoietic stem cell aging

Loss of protein quality is a driving force of aging1. The accumulation of misfolded proteins represents a vulnerability for long-lived cells, such as haematopoietic stem cells. How these cells, which have the ability to reconstitute all haematopoietic lineages throughout life2, maintain their regenerative potential and avert the effects of aging is poorly understood. Here, we determined the protein content in haematopoietic stem and progenitor cells to identify prevalent chaperones that support proteome integrity. We identified Peptidyl-Prolyl Isomerase A (PPIA or Cyclophilin A) as the dominant cytosolic foldase in this cell population. Loss of PPIA accelerated aging in the mouse stem cell compartment. In an effort to define targets of PPIA, we found that RNA- and DNA-binding proteins are common substrates of this chaperone. These proteins are enriched in intrinsically disordered regions (IDRs), which can catalyse protein condensation3. Isomerized target prolines are almost exclusively located within IDRs. We discovered that over 20% of PPIA client proteins are known to participate in liquid-liquid phase separation, enabling the formation of supramolecular membrane-less organelles. Using the poly-A binding protein PABPC1 as an example, we demonstrate that PPIA promotes phase separation of ribonucleoprotein particles, thereby increasing cellular stress resistance. Haematopoietic stem cell aging is associated with a decreased expression of PPIA and reduced synthesis of intrinsically disordered proteins. Our findings link the ubiquitously expressed chaperone PPIA to phase transition and identify macromolecular condensation as a potential determinant of the aging process in haematopoietic stem cells.

cell biology↗