Biology subjects

Hatch, G. M.

Publications and source records attributed to Hatch, G. M..

12 recordsLinked to original sources

bioRxiv2024

PI3K-dependant reprogramming of hexokinase isoforms controls glucose metabolism and functional responses of B lymphocytes

B lymphocyte metabolic reprogramming is essential for B cell differentiation and mounting a healthy immune response. The PI3K signaling pathway regulates B cell metabolism, but the mechanisms involved are not well understood. Here we report that signaling via PI3K8 can impact B cell glucose metabolism and immune functions via selective upregulation of hexokinase 2 (HK2). Three HK enzymes can catalyze the critical first step for glucose utilization and may selectively direct glucose into specific catabolic and anabolic pathways. While HK1 is constitutively expressed in B cells, HK2 is strikingly upregulated during B cell activation in a PI3K8-dependent manner. HK2 shows a unique distribution between mitochondrial and cytoplasmic pools that is also regulated by PI3K. Genetic deletion of HK2 significantly impairs extracellular acidification rate and glycolytic ATP production despite strong expression of HK1. B cell-specific deletion of HK2 in mice caused mild perturbations in B cell development but did not prevent generation of mature B cell subsets. HK2-deficient B cells show altered functional responses in vitro and evidence of metabolic adaptation to become less dependent on glucose and more dependent on glutamine. HK2-deficient B cells exhibit impaired glycolysis, altered metabolite profiles and altered flux of labeled glucose carbons into the pentose phosphate pathway. Upon immunization, HK2-deficient mice exhibit impaired generation of germinal centre B cells, plasmablasts and antibody responses. We further found that HK2 expression in primary human chronic lymphocytic leukemia (CLL) cells was associated with recent proliferation and could be reduced by PI3K inhibition. Our study identifies hexokinase 2 upregulation as a functionally important component of B cell metabolic reprogramming dependent on the PI3K pathway.

immunology↗

bioRxiv2023

Reduction in mRNA expression of the neutrophil chemoattract factor CXCL1 in Pseudomonas aeruginosa treated Barth Syndrome B lymphoblasts

Barth Syndrome (BTHS) is a rare X-linked genetic disease caused by a mutation in TAFAZZIN, a cardiolipin transacylase. Approximately 70% of patients with BTHS exhibit severe infections due to neutropenia. However, neutrophils from BTHS patients have been shown to exhibit normal phagocytosis and killing activity. B lymphocytes play a crucial role in the regulation of the immune system and when activated secret cytokines known to attract neutrophils to sites of infection. We examined expression of chemokine (C-X-C motif) ligand 1 (CXCL1), a known chemotactic for neutrophils, in Epstein-Barr virus transformed control and BTHS B lymphoblasts. Age-matched control and BTHS B lymphoblasts were incubated with Pseudomonas aeruginosa for 24 h and then cell viability, CD27+, CD24+, CD38+, CD138+ and PD1+ surface marker expression and CXCL1 mRNA expression determined. Cell viability was maintained in lymphoblasts incubated with a ratio of 50:1 bacteria:B cells. Surface marker expression was unaltered between control and BTHS B lymphoblasts. In contrast, CXCL1 mRNA expression was reduced approximately 90% (p<0.05) in untreated BTHS B lymphoblasts compared to control cells and approximately 70% (p<0.05) in bacterial treated BTHS B lymphoblasts compared to control cells. Thus, naive and bacterial-activated BTHS B lymphoblasts exhibit reduced mRNA expression of the neutrophil chemoattractant factor CXCL1. We suggest that impaired bacterial activation of B cells in some BTHS patients could promote immune dysfunction, and this may contribute to infections.

biochemistry↗

bioRxiv2023

Tafazzin knockdown in murine mesenchymal stem cells enhances the tafazzin knockdown mediated elevation in interleukin-10 secretion from murine B lymphocytes

Barth Syndrome is a rare X-linked genetic disorder caused by mutations in the TAFAZZIN gene. We recently demonstrated that tafazzin (Taz) protein deficiency in murine mesenchymal stems (MSCs) reduces immune function of activated wild type (WT) B lymphocytes. Interleukin-10 (IL-10) is a key anti-inflammatory cytokine capable of exerting immunosuppressive effects on myeloid cells. Here we examined if Taz deficiency in murine MSCs altered proliferation and IL-10 production in Taz deficient lipopolysaccharide (LPS)-activated murine B lymphocytes. Bone marrow MSCs and splenic B lymphocytes were isolated from WT or Taz knockdown (TazKD) mice. WT or Taz deficient MSCs were co-cultured with either LPS-activated WT or LPS-activated Taz deficient B lymphocytes for 24 h and B cell proliferation and IL-10 production determined. Taz deficient MSCs exhibited increased phosphatidylinositol-3-kinase (PI3K) mRNA expression compared to WT MSCs indicative of enhanced immunosuppression. Co-culture of Taz deficient MSCs with Taz deficient LPS-activated B cells resulted in a greater reduction in proliferation of B cells compared to Taz deficient MSCs co-cultured with LPS-activated WT B cells. In addition, co-culture of Taz deficient MSCs with Taz deficient LPS-activated B cells resulted in an enhanced production of IL-10 compared to Taz deficient MSCs co-cultured with LPS-activated WT B cells. Thus, Taz deficiency in murine MSCs potentiates the Taz knockdown-mediated elevation in IL-10 secretion from LPS-activated Taz knockdown B lymphocytes. These data suggest that Taz deficient MSCs may modulate the activity of other Taz deficient immune cells potentially promoting an enhanced immunosuppressive state.

immunology↗

bioRxiv2022

Tissue Specific Knockout of the Cardiolipin Transacylase Enzyme TAFAZZIN in Both Liver and Pancreatic Beta Cells Protects Mice From Diet-Induced Obesity

Mutations in the TAFAZZIN gene result in the X-linked genetic disease Barth Syndrome. The protein product tafazzin is a transacylase enzyme that remodels the phospholipid cardiolipin with fatty acids. Some Barth syndrome boys exhibit a lean phenotype. In addition, whole body knockdown of tafazzin in mice protects them from diet-induced obesity through increased hepatic fatty acid oxidation and reduced basal insulin secretion. We thus hypothesized that tafazzin deficiency in both the liver and beta cells of the pancreas contribute to this lean phenotype. Through a Cre-Lox approach we generated control, liver-specific, pancreatic beta cell-specific and liver and pancreatic beta cell-specific double knockout male mice. The animals were fed a high fat diet for 8 weeks and body weight, liver weight and fat pad weights determined. Liver-specific or pancreatic beta cell-specific male tafazzin knockout mice accumulated weight gain ({asymp}40% increase in body weight) at the same rate as control animals. In contrast, the liver- and beta cell-specific double tafazzin knockout mice exhibited a reduced rate of weight gain by 8 weeks ({asymp}26% increase in body weight) compared to control or the single tafazzin knockout animals. In addition, at 8 weeks the double tafazzin knockout mice exhibited reduced weight gain in tissues known to accumulate fat including the liver, the gonadal, inguinal and perirenal white adipose tissues and the brown adipose tissue. Thus, liver- and pancreatic beta cell-specific double tafazzin knockout male mice are protected from high fat diet induced weight gain and fat accumulation. These results may partially explain why some Barth Syndrome boys exhibit a lean phenotype.

biochemistry↗

bioRxiv2022

Reduction in cardiolipin reduces expression of creatine transporter-1 and creatine transport in hBMEC/D3 human brain microvessel endothelial cells

BackgroundCardiolipin (CL) is the signature phospholipid of mitochondria and regulates a plethora of cellular functions including mitochondrial energy production. There is little knowledge of how CL regulates uptake and membrane transport processes in mammalian cells. Endothelial cells of the blood brain barrier (BBB) play a vital role in uptake of metabolites into the brain and are enriched in mitochondria compared with peripheral endothelial cells. We examined how deficiency in BBB endothelial CL regulates the expression of selected drug and metabolite transporters and their function. MethodsCardiolipin synthase-1 (hCLS1) was knocked down in a human brain microvessel endothelial cell line, hBMEC/D3, by Lipofectamine(R) transfection with hCLS1 siRNA and CL levels, CL synthase activity and the mRNA expression of selected blood brain barrier drug and metabolite transporters examined. Mock transfected hBMEC/D3 cells served as controls. The incorporation of [14C]creatine and [14C]oleate into hBMEC/D3 cells was determined as a measure of solute metabolite transport and protein expression of the creatine transporter determined. ResultsKnockdown of the CL biosynthetic enzyme hCLS1 in hBMEC/D3 reduced CL and CL synthase activity and the mRNA expression of creatine transporter-1, p-glycoprotein and breast cancer resistance protein compared to controls. In contrast, mRNA expression of ATP binding cassette subfamily C members-1, -3, multidrug resistance-associated protein-4 variants 1, -2, and fatty acid transport protein-1 were unaltered. Although ATP production was unaltered by hCLS1 knockdown, incorporation of [14C]creatine into hBMEC/D3 cells was reduced compared to controls. The reduction in [14C]creatine incorporation was associated with a reduction in creatine transporter-1 protein expression. In contrast, incorporation of [14C]oleic acid into hBMEC/D3 cells and the mRNA expression of fatty acid transport protein-1 was unaltered by knockdown of hCLS1 compared to controls. ConclusionKnockdown of hCLS1 in hBMEC/D3, with a corresponding reduction in CL, results in alteration in expression of specific solute membrane transporters.

biochemistry↗

bioRxiv2021

Altered Cardiolipin Metabolism is Associated with Cardiac Mitochondrial Dysfunction in Pulmonary Vascular Remodeled Perinatal Rat Pups

BackgroundPulmonary vascular remodeling (PVR) in utero results in the development of heart failure (HF). The alterations that occur in cardiac lipid and mitochondrial bioenergetics during the development of in utero PVR was unknown. MethodsPVR was induced in pups in utero by exposure of pregnant dams to indomethacin and hypoxia. Cardiac lipids, echocardiographic function and cardiomyocyte mitochondrial function were subsequently examined. ResultsPerinatal rat pups with PVR exhibited elevated left and right cardiac ventricular internal dimensions and reduced ejection fraction and fractional shortening compared to controls. Cardiac myocytes from these pups exhibited increased glycolytic capacity and glycolytic reserve compared to controls. However, respiration with glucose as substrate was unaltered. Fatty acid oxidation and ATP-insensitive respiration were increased in isolated cardiac myocytes from these pups compared to controls indicating mitochondrial dysfunction. Although abundance of mitochondrial respiratory complexes were unaltered, increased trilinoleoyl-lysocardiolipin levels in these pups was observed. A compensatory increase in both cardiolipin (CL) and phosphatidylethanolamine (PE) content were observed due to increased synthesis of these phospholipids. ConclusionAlterations in cardiac cardiolipin and phospholipid metabolism in PVR rat pups is associated with the mitochondrial bioenergetic and cardiac functional defects observed in their hearts. Impact statement- Phospholipid metabolism was examined in pulmonary vascular remodeling in perinatal rat pups. - Pulmonary vascular remodeling was induced in utero by treating pregnant dams with hypoxia and indomethacin at 19-21 days of gestation. - The offspring exhibited altered pulmonary arterial remodeling with subsequent cardiac hypertrophy, ventricular dysfunction, cardiac myocyte mitochondrial dysfunction with altered fatty acid utilization. - In addition, the offspring exhibited elevated cardiolipin, lysocardiolipin and phosphatidylethanolamine content which may potentially contribute to the cardiac mitochondrial dysfunction.

biochemistry↗

bioRxiv2021

Tafazzin deficiency in mouse mesenchymal stem cells potentiates their immunosuppression and impairs activated B lymphocyte immune function

Barth Syndrome (BTHS) is a rare X-linked genetic disorder caused by mutation in the TAFAZZIN gene which encodes the cardiolipin (CL) transacylase tafazzin (Taz). Taz deficiency in BTHS patients results in reduced CL in their tissues and a neutropenia which contributes to the risk of infections. However, the impact of Taz deficiency in other cells of the immune system is poorly understood. Mesenchymal stem cells (MSCs) are well known for their immune inhibitory function. We examined whether Taz-deficiency in murine MSCs impacted their ability to modulate lipopolysaccharide (LPS)-activated wild type (WT) murine B lymphocytes. MSCs from tafazzin knockdown (TazKD) mice exhibited a 50% reduction in CL compared to wild type (WT) MSCs. However, mitochondrial oxygen consumption rate and membrane potential were unaltered. In contrast, TazKD MSCs exhibited increased glycolysis compared to WT MSCs and this was associated with elevated proliferation, phosphatidylinositol-3-kinase expression and expression of the immunosuppressive markers indoleamine-2,3-dioxygenase, cytotoxic T-lymphocyte-associated protein 4, interleukin-10, and cluster of differentiation 59. When co-cultured with LPS-activated WT B cells, TazKD MSCs inhibited B cell proliferation and growth rate and reduced B cell secretion of IgM to a greater extent than B cells co-cultured with WT MSCs. In addition, co-culture of LPS-activated WT B cells with TazKD MSCs induced B cell differentiation toward potent immunosuppressive phenotypes including interleukin-10 secreting plasma cells and B regulatory cells compared to activated B cells co-cultured with WT MSCs. These results indicate that Taz deficiency in MSCs enhances MSCs-mediated immunosuppression of activated B lymphocytes.

immunology↗

bioRxiv2021

Reduced protein kinase C delta association with a higher molecular weight complex in mitochondria of Barth Syndrome lymphoblasts

The protein kinase C delta (PKC{delta}) signalosome exists as a high molecular weight complex in mitochondria and controls mitochondrial oxidative phosphorylation. Barth Syndrome (BTHS) is a rare X-linked genetic disease in which mitochondrial oxidative phosphorylation is impaired due to a mutation in the gene TAFAZZIN which results in reduction in the phospholipid cardiolipin and an accumulation of monolysocardiolipin. Here we examined if PKC{delta} association with a higher molecular weight complex was altered in mitochondria of BTHS lymphoblasts. Immunoblot analysis of blue native-polyacrylamide gel electrophoresis mitochondrial fractions revealed that PKC{delta} associated with a higher molecular weight complex in control lymphoblasts but this was markedly reduced in BTHS patient B lymphoblasts in spite of an increase in PKC{delta} protein expression. We hypothesize that the lack of PKC{delta} within this higher molecular weight complex may contribute to defective mitochondrial PKC{delta} signaling and thus to the bioenergetic defects observed in BTHS.

biochemistry↗

bioRxiv2021

Tafazzin regulates the function of lipopolysaccharide activated B lymphocytes in mice

B lymphocytes are responsible for humoral immunity and play a key role in the immune response. Optimal mitochondrial function is required to support B cell activity during activation. We examined how deficiency of tafazzin, a cardiolipin remodeling enzyme required for mitochondrial function, alters the metabolic activity of B cells and their response to activation by lipopolysaccharide in mice. B cells were isolated from 3 month old wild type or tafazzin knockdown mice and incubated for up to 72 h with lipopolysaccharide and cell proliferation, expression of cell surface markers, secretion of antibodies and chemokines, proteasome and immunoproteasome activities, and metabolic function determined. In addition, proteomic analysis was performed to identify altered levels of proteins involved in survival, immunogenic, proteasomal and mitochondrial processes. Compared to wild type lipopolysaccharide activated B cells, lipopolysaccharide activated tafazzin knockdown B cells exhibited significantly reduced proliferation, lowered expression of cluster of differentiation 86 and cluster of differentiation 69 surface markers, reduced secretion of immunoglobulin M antibody, reduced secretion of keratinocytes-derived chemokine and macrophage-inflammatory protein-2, reduced proteasome and immunoproteasome activities, and reduced mitochondrial respiration and glycolysis. Proteomic analysis revealed significant alterations in key protein targets that regulate cell survival, immunogenicity, proteasomal processing and mitochondrial function consistent with the findings of the above functional studies. The results indicate that the cardiolipin transacylase enzyme tafazzin plays a key role in regulating mouse B cell function and metabolic activity during activation.

immunology↗

bioRxiv2020

Misoprostol Treatment Prevents Hypoxia-Induced Cardiac Dysfunction, Aberrant Cardiomyocyte Mitochondrial Dynamics and Permeability Transition Through Bnip3 Phosphorylation

Systemic hypoxia is a common element in most perinatal emergencies and is a known driver of Bnip3 expression in the neonatal heart. Bnip3 plays a prominent role in the evolution of necrotic cell death, disrupting ER calcium homeostasis and initiating mitochondrial permeability transition (MPT). Emerging evidence suggests a cardioprotective role for the prostaglandin E1 analogue misoprostol during periods of hypoxia, but the mechanisms for this protection are not completely understood. Using a combination of mouse and cell models, we tested if misoprostol is cardioprotective during neonatal hypoxic injury by altering Bnip3 function. Here we report that hypoxia elicits mitochondrial-fragmentation, MPT, reduced ejection fraction, and evidence of necroinflammation, which were abrogated with misoprostol treatment or Bnip3 knockout. Through molecular studies we show that misoprostol leads to PKA-dependent Bnip3 phosphorylation at threonine-181, and subsequent redistribution of Bnip3 from mitochondrial Opa1 and the ER through an interaction with 14-3-3 proteins. Taken together, our results demonstrate a role for Bnip3 phosphorylation in the regulation of cardiomyocyte contractile/metabolic dysfunction, and necroinflammation. Furthermore, we identify a potential pharmacological mechanism to prevent neonatal hypoxic injury.

cell biology↗

bioRxiv2020

Berberine alleviates adiposity and cardiac dysfunction in offspring exposed to gestational diabetes mellitus

The most robust risk factor for type 2 diabetes in childhood is prior exposure to diabetes during gestation. Currently, there are few evidence-based strategies to attenuate the of risk of metabolic syndrome in offspring exposed to gestational diabetes mellitus (GDM). Berberine (BBR) is an isoquinoline alkaloid extracted from Chinese herbs and exhibits glucose lowering properties. It has been used safely for centuries in humans. Our objective was to determine whether BBR treatment improves health outcomes in the mouse offspring of GDM dams. Dams were fed either a lean low-fat diet (Lean, LF,10% kcal fat) or a GDM-inducing high-fat/high sucrose diet (GDM, HF, 45% kcal fat) prior to breeding and throughout pregnancy. The resulting Lean and GDM-exposed offspring were randomly assigned a LF, HF or HF diet containing BBR (160 mg/kg/d) for 12 weeks. We determined that BBR treatment significantly reduced body weight ([~]20%), % body fat ([~]40%) and gonadal fat pad mass ([~]60%) compared to HF-fed GDM offspring. Furthermore, BBR treatment of HF-fed GDM offspring normalized insulin levels in the plasma and isolated pancreatic islets. Differences in food consumption did not contribute to altered body composition in BBR treated mice, as levels remained similar between experimental groups. Alternatively, BBR-treatment was associated with increased whole-body oxygen consumption (VO2), activity and heat production. Additionally, we determined that HF-fed GDM offspring developed a cardiomyopathy, characterized by increased isovolumetric contraction ([~]150%, IVCT), relaxation time ([~]70%, IVRT), elevated cardiac triglyceride ([~]120%) and reduced mitochondrial function (30%, spare capacity) compared to LF fed Lean controls. BBR treatment normalized heart function, reduced triglyceride levels and maintained mitochondrial function. Our data supports BBR as a potential pharmacotherapeutic approach to improve health outcomes in individuals exposed to GDM. Key Points SummaryO_LIGestational diabetes mellitus is a common metabolic complication of pregnancy which is increasing worldwide due to the prevalence of obesity. C_LIO_LIIt is known that individuals exposed to gestational diabetes have elevated risk of developing metabolic syndrome however there are few evidence-based strategies which provide protection. C_LIO_LIBerberine is a natural compound found in Chinese herbs which has been safely used for centuries to treat type 2 diabetes mellitus. C_LIO_LIWe determined that berberine treatment of offspring exposed to gestational diabetes attenuated weight gain, reduced insulin levels and normalized both heart and pancreatic function. C_LIO_LIOur data supports berberine as a potential pharmacotherapeutic approach to improve health outcomes in individuals exposed to gestational diabetes. C_LI

physiology↗

bioRxiv2018

Misoprostol regulates Bnip3 repression and alternative splicing to control cellular calcium homeostasis during hypoxic stress.

The cellular response to hypoxia involves the activation of a conserved pathway for gene expression regulated by the transcription factor complex called hypoxia-inducible factor (HIF). This pathway has been implicated in both the adaptive response to hypoxia and in several hypoxic-ischemic related pathologies. Perinatal hypoxic injury, often associated with prematurity, leads to multi-organ dysfunction resulting in significant morbidity and mortality. Using a rodent model of neonatal hypoxia and several representative cell lines, we observed HIF1 activation and down-stream induction of the cell death gene Bnip3 in brain, large intestine, and heart which was mitigated by administration of the prostaglandin E1 analog misoprostol. Mechanistically, we determined that misoprostol inhibits full-length Bnip3 (Bnip3-FL) expression through PKA-mediated NF-{kappa}B (P65) nuclear retention, and the induction of pro-survival splice variants. We observed that the dominant small pro-survival variant of Bnip3 in mouse cells lacks the third exon (Bnip3{Delta}Exon3), whereas human cells produce a pro-survival BNIP3 variant lacking exon 2 (BNIP3{Delta}Exon2). In addition, these small Bnip3 splice variants prevent mitochondrial dysfunction, permeability transition, and necrosis triggered by Bnip3-FL by blocking calcium transfer from the sarco/endoplasmic reticulum to the mitochondria. Furthermore, misoprostol and Bnip3{Delta}Exon3 promote nuclear calcium accumulation, resulting in HDAC5 nuclear export, NFAT activation, and adaptive changes in cell morphology and gene expression. Collectively, our data suggests that misoprostol can mitigate the potential damaging effects of hypoxia on multiple cell types by activating adaptive cell survival pathways through Bnip3 repression and alternative splicing.

cell biology↗