CD4 Knockout Research Articles

Constitutive Vagus Nerve Activation Modulates Immune Suppression in Sepsis Survivors.

Patients surviving a septic episode exhibit persistent immune impairment and increased mortality due to enhanced vulnerability to infections. In the present study, using the cecal ligation and puncture (CLP) model of polymicrobial sepsis, we addressed the hypothesis that altered vagus nerve activity contributes to immune impairment in sepsis survivors. CLP-surviving mice exhibited less TNFα in serum following administration of LPS, a surrogate for an infectious challenge, than control-operated (control) mice. To evaluate the role of the vagus nerve in the diminished response to LPS, mice were subjected to bilateral subdiaphragmatic vagotomy at 2 weeks post-CLP. CLP-surviving vagotomized mice exhibited increased serum and tissue TNFα levels in response to LPS-challenge compared to CLP-surviving, non-vagotomized mice. Moreover, vagus nerve stimulation in control mice diminished the LPS-induced TNFα responses while having no effect in CLP mice, suggesting constitutive activation of vagus nerve signaling in CLP-survivors. The percentage of splenic CD4+ ChAT-EGFP+ T cells that relay vagus signals to macrophages was increased in CLP-survivors compared to control mice, and vagotomy in CLP-survivors resulted in a reduced percentage of ChAT-EGFP+ cells. Moreover, CD4 knockout CLP-surviving mice exhibited an enhanced LPS-induced TNFα response compared to wild-type mice, supporting a functional role for CD4+ ChAT+ T cells in mediating inhibition of LPS-induced TNFα responses in CLP-survivors. Blockade of the cholinergic anti-inflammatory pathway with methyllcaconitine, an α7 nicotinic acetylcholine receptor antagonist, restored LPS-induced TNFα responses in CLP-survivors. Our study demonstrates that the vagus nerve is constitutively active in CLP-survivors and contributes to the immune impairment.

Dipeptidyl Peptidase-4 Is a Pro-Recovery Mediator During Acute Hepatotoxic Damage and Mirrors Severe Shifts in Kupffer Cells.

Dipeptidyl peptidase‐4 (DPP‐4 or clusters of differentiation [CD]26) is a multifunctional molecule with established roles in metabolism. Pharmacologic inhibition of DPP‐4 is widely used to improve glycemic control through regulation of the incretin effect. Colaterally, CD26/DPP‐4 inhibition appears to be beneficial in many inflammatory conditions, namely in delaying progression of liver pathology. Nevertheless, the exact implications of CD26/DPP‐4 enzymatic activity in liver dysfunction remain unclear. In this work, we investigated the involvement of CD26/DPP‐4 in experimental mouse models of induced hepatocyte damage that severely impact Kupffer cell (KC) populations. Liver dysfunction was evaluated in CD26 knockout (KO) and B6 wild‐type mice during acute liver damage induced by acetaminophen, chronic liver damage induced by carbon tetrachloride, and KC‐depleting treatment with clodronate‐loaded liposomes. We found that necrosis resolution after hepatotoxic injury was delayed in CD26KO mice and in B6 mice treated with the CD26/DPP‐4 inhibitor sitagliptin, suggesting that DPP‐4 enzymatic activity plays a role in recovering from acute liver damage. Interestingly, the severe KC population reduction in acute and chronic liver injury was concomitant with increased CD26/DPP‐4 serum levels. Remarkably, both chronic liver damage and noninflammatory depletion of KCs by clodronate liposomes were marked by oscillation in CD26/DPP‐4 serum activity that mirrored the kinetics of liver KC depletion/recovery. Conclusion:CD26/DPP‐4 enzymatic activity contributes to necrosis resolution during recovery from acute liver injury. Serum CD26/DPP‐4 is elevated when severe perturbations are imposed on KC populations, regardless of patent liver damage. We propose that serum CD26/DPP‐4 is a potential systemic surrogate marker of severe impairments in the KC population imposed by clinical and subclinical liver conditions.

Knockdown of cd44 decreases attachment but not invasion of endometrial epithelial cells

Previously, we showed decreased development of endometriotic lesions in CD44 knockout mice compared to control.1 This suggests that the CD44/hyaluronic acid (HA) system plays a role in the development of the early endometriotic lesion. Here, we assess the in vitro effects of CD44 knockdown (KD) on endometrial epithelial cells (EECs) through attachment to and invasion through a peritoneal mesothelial cell (PMC) monolayer. We also investigate the expression of the receptor for hyaluronic acid mediated motility (RHAMM), another receptor for hyaluronic acid. In vitro studies. Primary EECs were isolated from menstrual endometrial biopsies. EECs were immortalized (iEECs) by telomerase vector, and verified by genotyping. CD44 KD in iEECs was created by CRISPR technique and verified through flow cytometry and western blot. Established in vitro assays were used to assess iEEC attachment to PMCs and invasion through a monolayer of PMCs on a matrigel matrix. Results were analyzed with student t-tests. CD44 KD iEECs demonstrate decreased in vitro attachment to PMCs compared to control (p=0.008). CD44 KD iEECs increased in vitro invasion to PMC compared to control (p= 0.001). In CD44 KD iEECs, RHAMM mRNA expression increases compared to control (p<0.001). Our finding that CD44 KD decreases attachment to PMCs further supports the involvement of CD44/HA in the development of the early endometriotic lesion. The increase in invasiveness of CD44 KD and the compensatory increase in RHAMM suggest that other CD44 ligands are involved in endometrial cell invasion.

Elimination of donor CD47 protects against vascularized allograft rejection in mice.

CD47 is a ubiquitously expressed transmembrane glycoprotein that plays a complex role in regulation of cell survival and function. We have previously shown that the interspecies incompatibility of CD47 plays an important role in triggering rejection of cellular xenografts by macrophages. However, the role of CD47 in solid organ transplantation remains undetermined. Here, we explored this question in mouse models of heart allotransplantation. We observed that the lack of CD47 in donor hearts had no deleterious effect on graft survival in syngeneic or single MHC class I-mismatched recipients, in which both wild-type (WT) and CD47 knockout (CD47 KO) mouse hearts survived long term with no sign of rejection. Paradoxically, elimination of donor CD47 was beneficial for graft survival in signal MHC class II- and class I- plus class II-mismatched combinations, in which CD47 KO donor hearts showed significantly improved survival compared to WT donor hearts. Similarly, CD47 KO donor hearts were more resistant than WT hearts to humoral rejection in α1,3-galactosyltransferase-deficient mice. Moreover, a significant prolongation of WT allografts was observed in recipient mice treated with antibodies against a CD47 ligand thrombospondin-1 (TSP1) or with TSP1 deficiency, indicating that TSP1-CD47 signaling may stimulate vascularized allograft rejection. Thus, unlike cellular transplantation, donor CD47 expression may accelerate the rejection of vascularized allografts.

Abstract 296: Cd38 Deficiency Protects Heart From Lipid Overload-induced Oxidative Stress via Activating Sirt3/foxo3 Pathway

Background/Aims: Our and other studies showed that CD38 deficiency protected heart from ischemia/reperfusion injury and high fat diet (HFD)-induced obesity in mice, respectively. However, the roles of CD38 in lipid overload-induced heart injury were not evaluated. In the present study, we investigated the preventive effects and mechanisms of CD38 deficiency on mouse heart injury induced by HFD. Methods: The discrepant metabolites in heart from wild type (WT) and CD38 knockout (CD38 -/- ) mice fed with HFD were examined using metabolomics analysis. The cell viability, the lactate hydrogenase (LDH) release, super oxide dismutase (SOD) activity, reactive oxygen species (ROS) production, triglyceride concentration and the expressions of various corresponding genes were examined for evaluating the effects of CD38 on oleic acid (OA)-induced cell injury using CD38 knockdown H9C2 stable cell line. Results: Our results revealed that CD38 deficiency significantly elevated the intracellular glutathione (GSH) concentration and GSH/GSSG ratio, decreased the contents of various free fatty acids and increased intracellular NAD + level in heart of CD38 -/- mice fed with HFD. Knockdown of CD38 significantly attenuated OA-induced cell injury, ROS production and lipid synthesis, seen as enhancing cell viability, reducing LDH release, elevating SOD activity, and decreasing triglyceride content and expressions of FASN in the CD38 knockdown H9C2 stable cell line. In addition, we also observed that the mitochondrial deacetylase Sirt3 and its target genes FOXO3 and SOD2 were upregulated in the stable cell lines after OA stimulation. Furthermore, the expressions of NOX2 and NOX4 were attenuated, accompanied by decreasing Bax expression and increasing Bcl-2 expression in the cells after OA stimulation. Conclusions: Our results demonstrated that CD38 deficiency protected heart from HFD-induced oxidative stress via activating Sirt3/FOXO3-mediated anti-oxidative stress pathway.

Protective role of commensal bacteria in Sjögren Syndrome

CD25 knock-out (CD25KO) mice spontaneously develop Sjögren Syndrome (SS)-like inflammation. We investigated the role of commensal bacteria by comparing CD25KO mice housed in conventional or germ-free conditions. Germ-free CD25KO mice have greater corneal barrier dysfunction, lower goblet cell density, increased total lymphocytic infiltration score, increased expression of IFN-γ, IL-12 and higher a frequency of CD4+IFN-γ+ cells than conventional mice. CD4+ T cells isolated from female germ-free CD25KO mice adoptively transferred to naive immunodeficient RAG1KO recipients caused more severe Sjögren-like disease than CD4+ T cells transferred from conventional CD25KO mice. Fecal transplant in germ-free CD25KO mice reversed the spontaneous dry eye phenotype and decreased the generation of pathogenic CD4+IFN-γ+ cells. Our studies indicate that lack of commensal bacteria accelerates the onset and severity of dacryoadenitis and generates autoreactive CD4+T cells with greater pathogenicity in the CD25KO model, suggesting that the commensal bacteria or their metabolites products have immunoregulatory properties that protect exocrine glands in the CD25KO SS model.

Maternal Behavior of CD38 Knockout Dams is Improved by Social Support

Maternal Behavior of CD38 Knockout Dams is Improved by Social Support

Microvascular Dysfunction Following Multiwalled Carbon Nanotube Exposure Is Mediated by Thrombospondin-1 Receptor CD47.

Pulmonary exposure to multiwalled carbon nanotubes (MWCNTs) disrupts peripheral microvascular function. Thrombospondin-1 (TSP-1) is highly expressed during lung injury and has been shown to alter microvascular reactivity. It is unclear exactly how TSP-1 exerts effects on vascular function, but we hypothesized that the TSP-1 receptor CD47 may mediate changes in vasodilation. Wildtype (WT) or CD47 knockout (CD47 KO) C57B6/J-background animals were exposed to 50 µg of MWCNT or saline control via pharyngeal aspiration. Twenty-four hours postexposure, intravital microscopy was performed to assess arteriolar dilation and venular leukocyte adhesion and rolling. To assess tissue redox status, electron paramagnetic resonance and NOx measurements were performed, while inflammatory biomarkers were measured via multiplex assay.Vasodilation was impaired in the WT + MWCNT group compared with control (57 ± 9 vs 90 ± 2% relaxation), while CD47 KO animals showed no impairment (108 ± 8% relaxation). Venular leukocyte adhesion and rolling increased by >2-fold, while the CD47 KO group showed no change. Application of the antioxidant apocynin rescued normal leukocyte activity in the WT + MWCNT group. Lung and plasma NOx were reduced in the WT + MWCNT group by 47% and 32%, respectively, while the CD47 KO groups were unchanged from control. Some inflammatory cytokines were increased in the CD47 + MWCNT group only. In conclusion, TSP-1 is an important ligand mediating MWCNT-induced microvascular dysfunction, and CD47 is a component of this dysregulation. CD47 activation likely disrupts nitric oxide (•NO) signaling and promotes leukocyte-endothelial interactions. Impaired •NO production, signaling, and bioavailability is linked to a variety of cardiovascular diseases in which TSP-1/CD47 may play an important role.

CD4+ T cells are activated in regional lymph nodes and migrate to skin to initiate lymphedema

T cell-mediated responses have been implicated in the development of fibrosis, impaired lymphangiogenesis, and lymphatic dysfunction in secondary lymphedema. Here we show that CD4+ T cells are necessary for lymphedema pathogenesis by utilizing adoptive transfer techniques in CD4 knockout mice that have undergone tail skin and lymphatic excision or popliteal lymph node dissection. We also demonstrate that T cell activation following lymphatic injury occurs in regional skin-draining lymph nodes after interaction with antigen-presenting cells such as dendritic cells. CD4+ T cell activation is associated with differentiation into a mixed T helper type 1 and 2 phenotype, as well as upregulation of adhesion molecules and chemokines that promote migration to the skin. Most importantly, we find that blocking T cell release from lymph nodes using a sphingosine-1-phosphate receptor modulator prevents lymphedema, suggesting that this approach may have clinical utility.

The Role of B7-CD28 and CD40L-CD40 costimulatory signaling in thymic Invariant NKT Cell subset development

Abstract Invariant Natural Killer T (iNKT) cells are a unique subset of NKT cells that express a highly restricted αβ T cell receptor (TCR) and are selected in the thymus by recognition of Glycolipid/CD1d complex expressed by double-positive thymocytes. We previously demonstrated that thymic iNKT cell development is highly sensitive to B7-CD28 costimulatory interactions, with substantially decreased numbers of thymic iNKT cells in B7 and CD28 knockout mice. Advances in iNKT subset identification have allowed the detailed study of three major iNKT subsets, NKT1, NKT2, and NKT17, defined by characteristic transcription factor expression. We have analyzed the requirement for B7-CD28 and CD40-CD40L costimulatory signaling for development of thymic iNKT subsets. Comparison of BALB/c wild-type, B7 knockout, and CD28 knockout mice showed a substantial decrease in number of all thymic iNKT subsets in B7 and CD28 knockouts, demonstrating a critical role for B7-CD28 signaling in development of all thymic iNKT subsets. In contrast, CD40 knockout and CD40L knockout mice showed a substantial selective decrease in NKT2 cells with less effect on NKT1 and NKT17 subsets. These findings identify distinct requirements for B7-CD28 costimulation in thymic development of all iNKT subsets and for CD40L-CD40 costimulation selectively in NKT2 subset development. Further experiments are currently in progress examining the cellular requirements for B7 and CD40 expression in NKT development using conditional B7 and CD40 knockouts and complementary bone marrow mixed chimera approaches.

CD40 expression on specific antigen-presenting cells mediates experimental autoimmune encephalomyelitis

Abstract CD40 is a cell surface receptor that belongs tothe tumor necrosis factor receptor (TNFR) family and serves as a costimulatory molecule on the antigen presenting cells (APCs). The interaction between CD40 on B cells and its ligand CD154 on activated T helper cells is known to be essential for the development of thymus-dependent humoral immunity. Administration of blocking anti-CD40L antibody or CD40 gene knockout make mice resistant to experimental autoimmune encephalomyelitis(EAE), an animal model of human multiple sclerosis (MS), but the complex cellular interactions mediating the role of CD40 in EAE are not fully understood. We are using conditional CD40 knockout mice to selectively delete CD40 on specific APC populations and evaluate the effects by recombinant human MOG (rhMOG) induced EAE, a model is both T cell and B cell dependent. We found that conditional knockout of CD40 on B cells or dendritic cells led to significantly reduced severity of EAE. Studies of the mechanisms mediating CD40 function in immune response and CNS immunopathology are underway.

The glycoprotein GPNMB attenuates astrocyte inflammatory responses through the CD44 receptor

BackgroundNeuroinflammation is one of the hallmarks of neurodegenerative diseases, such as Parkinson’s disease (PD). Activation of glial cells, including microglia and astrocytes, is a characteristic of the inflammatory response. Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane glycoprotein that releases a soluble signaling peptide when cleaved by ADAM10 or other extracellular proteases. GPNMB has demonstrated a neuroprotective role in animal models of ALS and ischemia. However, the mechanism of this protection has not been well established. CD44 is a receptor expressed on astrocytes that can bind GPNMB, and CD44 activation has been demonstrated to reduce NFκB activation and subsequent inflammatory responses in macrophages. GPNMB signaling has not been investigated in models of PD or specifically in astrocytes. More recently, genetic studies have linked polymorphisms in GPNMB with risk for PD. Therefore, it is important to understand the role this signaling protein plays in PD.MethodsWe used data mining techniques to evaluate mRNA expression of GPNMB and its receptor CD44 in the substantia nigra of PD and control brains. Immunofluorescence and qPCR techniques were used to assess GPNMB and CD44 levels in mice treated with MPTP. In vitro experiments utilized the immortalized mouse astrocyte cell line IMA2.1 and purified primary mouse astrocytes. The effects of recombinant GPNMB on cytokine-induced astrocyte activation was determined by qPCR, immunofluorescence, and measurement of nitric oxide and reactive oxygen production.ResultsIncreased GPNMB and CD44 expression was observed in the substantia nigra of human PD brains and in GFAP-positive astrocytes in an animal model of PD. GPNMB treatment attenuated cytokine-induced levels of inducible nitric oxide synthase, nitric oxide, reactive oxygen species, and the inflammatory cytokine IL-6 in an astrocyte cell line and primary mouse astrocytes. Using primary mouse astrocytes from CD44 knockout mice, we found that the anti-inflammatory effects of GPNMB are CD44-mediated.ConclusionsThese results demonstrate that GPNMB may exert its neuroprotective effect through reducing astrocyte-mediated neuroinflammation in a CD44-dependent manner, providing novel mechanistic insight into the neuroprotective properties of GPNMB.

Genetic deletion of CD38 confers post-ischemic myocardial protection through preserved pyridine nucleotides

Following the onset of ischemia/reperfusion (I/R), CD38 activation occurs and is associated with depletion of NAD(P)(H) in the heart as well as myocardial injury and endothelial dysfunction. Studies with pharmacological inhibitors suggest that the NADP+-hydrolyzing ability of CD38 can deplete the NAD(P)(H) pools. However, there is a need for more specific studies on the importance of CD38 and its role in the process of endothelial dysfunction and myocardial injury in the post-ischemic heart. Therefore, experiments were performed in hearts of mice with global gene knockout of CD38. Isolated perfused CD38−/− and wild type (WT) mouse hearts were studied to determine the link between CD38 activation, the levels of NADP(H), endothelial dysfunction, and myocardial injury after I/R. Genetic deletion of CD38 preserves the myocardial and endothelial NADP(H) pools compared to WT. Whole heart BH4 levels in CD38−/− hearts were also preserved. Post-ischemic levels of cGMP were greatly depleted in WT hearts, but preserved to near baseline levels in CD38−/− hearts. The preservation of these metabolite pools in CD38−/− hearts was accompanied by near full recovery of NOS-dependent coronary flow, while in WT hearts, severe impairment of endothelial function and NOS uncoupling occurred with decreased NO and enhanced superoxide generation. CD38−/− hearts also exhibited marked protection against I/R with preserved glutathione levels, increased recovery of left ventricular contractile function, decreased myocyte enzyme release, and decreased infarct size. Thus, CD38 activation causes post-ischemic depletion of NADP(H) within the heart, with severe depletion from the endothelium, resulting in endothelial dysfunction and myocardial injury.

Inhibition of the cluster of differentiation 14 innate immunity pathway with IAXO-101 improves chronic microelectrode performance

Objective. Neuroinflammatory mechanisms are hypothesized to contribute to intracortical microelectrode failures. The cluster of differentiation 14 (CD14) molecule is an innate immunity receptor involved in the recognition of pathogens and tissue damage to promote inflammation. The goal of the study was to investigate the effect of CD14 inhibition on intracortical microelectrode recording performance and tissue integration. Approach. Mice implanted with intracortical microelectrodes in the motor cortex underwent electrophysiological characterization for 16 weeks, followed by endpoint histology. Three conditions were examined: (1) wildtype control mice, (2) knockout mice lacking CD14, and (3) wildtype control mice administered a small molecule inhibitor to CD14 called IAXO-101. Main results. The CD14 knockout mice exhibited acute but not chronic improvements in intracortical microelectrode performance without significant differences in endpoint histology. Mice receiving IAXO-101 exhibited significant improvements in recording performance over the entire 16 week duration without significant differences in endpoint histology. Significance. Full removal of CD14 is beneficial at acute time ranges, but limited CD14 signaling is beneficial at chronic time ranges. Innate immunity receptor inhibition strategies have the potential to improve long-term intracortical microelectrode performance.

Anti-nociceptive Role of CXCL1 in a Murine Model of Peripheral Nerve Injury-induced Neuropathic Pain

Both spinal cord infiltrating CD4+ T lymphocytes and microglial CD40 contribute to the maintenance of neuropathic pain-like behaviors induced by spinal nerve L5 transection (L5Tx), a murine model of neuropathic pain. Here, we sought to investigate the involvement of multiple chemokines in microglial CD40-mediated and CD4+ T lymphocytes-mediated L5Tx-induced sensory hypersensitivity. Spinal cord chemokine expression in CD4 knockout (KO), CD40 KO, and wild type (WT) BALB/c mice was determined at the protein level via multiplex assays and at the RNA level via quantitative real-time PCR. In WT mice, L5Tx induced significant increases in CCL2, CCL3, and CCL5 expression (protein and RNA) up to day 21 post-L5Tx, while CD4 KO mice displayed blunted, predominantly non-significant, responses in these chemokines at protein levels post-L5Tx. L5Tx also induced increased expression of these chemokines in CD40 KO mice; however, the overall protein levels of these chemokines were significantly lower than those in WT mice. Further, L5Tx induced a significant increase in CXCL1 at the protein level and in CXCR2 at RNA level only in CD40 KO mice. Intrathecal administration of CXCL1 in WT mice significantly reduced L5Tx-induced mechanical hypersensitivity. CD40 KO mice also displayed higher levels of Ly6G (neutrophil marker) RNA expression in the lumbar spinal cord post-L5Tx. Altogether, our data suggest that CD4+ T lymphocytes and microglial CD40 mediate their pro-nociceptive effects in part by promoting selected chemokine responses, and more importantly, CXCL1 can play an anti-nociceptive role in peripheral nerve injury-induced neuropathic pain, which is possibly mediated by infiltrating neutrophils.

CRISPR/Cas9-mediated knockout of CD47 causes hemolytic anemia with splenomegaly in C57BL/6 mice

CD47 (integrin-associated protein), a multi-spanning transmembrane protein expressed in all cells including red blood cells (RBCs) and leukocytes, interacts with signal regulatory protein α (SIRPα) on macrophages and thereby inhibits phagocytosis of RBCs. Recently, we generated a novel C57BL/6J CD47 knockout (CD47-/- hereafter) mouse line by employing a CRISPR/Cas9 system at Center for Mouse Models of Human Disease, and here report their hematological phenotypes. On monitoring their birth and development, CD47-/- mice were born viable with a natural male-to-female sex ratio and normally developed from birth through puberty to adulthood without noticeable changes in growth, food/water intake compared to their age and sex-matched wild-type littermates up to 26 weeks. Hematological analysis revealed a mild but significant reduction of RBC counts and hemoglobin in 16 week-old male CD47-/- mice which were aggravated at the age of 26 weeks with increased reticulocyte counts and mean corpuscular volume (MCV), suggesting hemolytic anemia. Interestingly, anemia in female CD47-/- mice became evident at 26 weeks, but splenomegaly was identified in both genders of CD47-/- mice from the age of 16 weeks, consistent with development of hemolytic anemia. Additionally, helper and cytotoxic T cell populations were considerably reduced in the spleen, but not in thymus, of CD47-/- mice, suggesting a crucial role of CD47 in proliferation of T cells. Collectively, these findings indicate that our CD47-/- mice have progressive hemolytic anemia and splenic depletion of mature T cell populations and therefore may be useful as an in vivo model to study the function of CD47.

CD38-cADPR-SERCA Signaling Axis Determines Skeletal Muscle Contractile Force in Response to β-Adrenergic Stimulation

Background/Aims: Cyclic ADP-ribose (cADPR) is a Ca²⁺ -mobilization messenger that acts on ryanodine-sensitive Ca²⁺ channels in the sarcoplasmic reticulum (SR) Ca²⁺ stores. Moreover, it has been proposed that cADPR serves an additional role in activating the sarcoendoplasmic reticulum Ca²⁺ -ATPase (SERCA) pump. The aim of this study was to determine the exact mechanism by which cADPR regulates SR Ca²⁺ stores in physiologically relevant systems. Methods: We analyzed Ca²⁺ signals as well as the production of Ca²⁺ mobilizing messengers in the skeletal muscle cells of mice subjected to intensive exercise or in the SR fractions from skeletal muscle cells after β-adrenergic receptor (β-AR) stimulation. Results: We show that cADPR enhances SERCA activity in skeletal muscle cells in response to β-AR agonists, increasing SR Ca²⁺ uptake. We demonstrate that cADPR is generated by CD38, a cADPR-synthesizing enzyme, increasing muscle Ca²⁺ signals and contractile force during exercise. CD38 is upregulated by the cAMP response element–binding protein (CREB) transcription factor upon β-AR stimuli and exercise. CD38 knockout (KO) mice show defects in their exercise and cADPR synthesis capabilities, lacking a β-AR agonist-induced muscle contraction when compared to wild-type mice. The skeletal muscle of CD38 KO mice exhibits delayed cytosolic Ca²⁺ clearance and reduced SERCA activity upon exercise. Conclusion: These findings provide insight into the physiological adaptive mechanism by which the CD38- cADPR-SERCA signaling axis plays an essential role in muscle contraction under exercise, and define cADPR as an endogenous activator of SERCA in enhancing the SR Ca²⁺ load.

CD38 Deficiency Protects Heart from High Fat Diet-Induced Oxidative Stress Via Activating Sirt3/FOXO3 Pathway

Background/Aims: Previous studies showed that CD38 deficiency protected heart from ischemia/reperfusion injury and high fat diet (HFD)-induced obesity in mice. However, the role of CD38 in HFD-induced heart injury remains unclear. In the present study, we have investigated the effects and mechanisms of CD38 deficiency on HFD-induced heart injury. Methods: The metabolites in heart from wild type (WT) and CD38 knockout (CD38^-/-) mice were examined using metabolomics analysis. Cell viability, lactate hydrogenase (LDH) release, super oxide dismutase (SOD) activity, reactive oxygen species (ROS) production, triglyceride concentration and gene expression were examined by biochemical analysis and QPCR. Results: Our results revealed that CD38 deficiency significantly elevated the intracellular glutathione (GSH) concentration and GSH/GSSG ratio, decreased the contents of free fatty acids and increased intracellular NAD⁺ level in heart from CD38^-/- mice fed with HFD. In addition, in vitro knockdown of CD38 significantly attenuated OA-induced cellular injury, ROS production and lipid synthesis. Furthermore, the expression of mitochondrial deacetylase Sirt3 as well as its target genes FOXO3 and SOD2 were markedly upregulated in the H9C2 cell lines after OA stimulation. In contrast, the expressions of NOX2 and NOX4 were significantly decreased in the cells after OA stimulation. Conclusion: Our results demonstrated that CD38 deficiency protected heart from HFD-induced oxidative stress via activating Sirt3/FOXO3-mediated anti-oxidative stress pathway.

Glutathione and Inter-α-trypsin inhibitor heavy chain 3 (Itih3) mRNA levels in nicotine-treated Cd44 knockout mice.

Cluster of differentiation 44 (Cd44), a hyaluronan receptor, and the secreted hyaluronan-binding protein Inter-α-trypsin Inhibitor Heavy chain 3 (Itih3) play an important role in cancer and oxidative stress. Smoking of tobacco reduces Itih3 in the plasma and activates hyaluronan signaling through Cd44, but the impact of Cd44 on Itih3 expression is unknown. Here, we studied changes induced by the tobacco component nicotine on the glutathione (GSH) antioxidant system and Itih3 gene expression in Cd44 knockout mice. Cd44 deficiency decreased baseline total GSH and oxidized glutathione (GSSG) levels in the liver compared to wildtype mice. However, contrary to wildtype mice, chronic oral nicotine administration (200 μg/ml) failed to further reduce total GSH and GSSG in Cd44 mice. Sex differences with lowered glutathione levels in females was also detectable only in wildtype but not Cd44 knockout mice. Itih3 mRNA levels in the liver and hypothalamus were not affected by nicotine, Cd44 genotype or sex. Nonetheless, the correlation between Itih3 and total GSH levels in the liver (r = 0.42, p < 0.05) suggested a role of Itih3 in glutathione metabolism in WT mice. Again this effect was diminished in Cd44 knockout mice. The disappearance of nicotine effects, sex differences and correlations between Itih3 and total GSH in Cd44 knockout mice compared to wildtype animals suggests an interaction between nicotine, Cd44 and/or sex-dependent signaling in the regulation of glutathione metabolism.

CRISPR-Cas9-Mediated Silencing of CD44 in Human Highly Metastatic Osteosarcoma Cells

Background/Aims: Metastasis is the major cause of death in patients with osteosarcoma. There is an urgent need to identify molecular markers that promote metastasis. Cluster of differentiation 44 is a receptor for hyaluronic acid (HA) and HA-binding has been proven to participate in various biological tumor activities, including tumor progression and metastasis. Methods: We performed a meta-analysis to investigate the relationship between CD44 expression, survival, and metastasis in patients with osteosarcoma. We then utilized the CRISPR-Cas9 system to specifically silence CD44 in highly metastatic human osteosarcoma cells (MNNG/HOS and 143B) and further determined the functional effects of CD44 knockout in these cells. Results: The meta-analysis demonstrated that a high level of CD44 may predict poor survival and higher potential of metastasis in patients with osteosarcoma. The expression of CD44 in highly metastatic human osteosarcoma cell lines was efficiently blocked by CRISPR-Cas9. When CD44 was silenced, the proliferation and spheroid formation of these osteosarcoma cells was inhibited under 3-D culture conditions. Furthermore, the migratory and invasive functions were also impaired in these highly metastatic osteosarcoma cells. Conclusion: These results suggest that developing new strategies to target CD44 in osteosarcoma may prevent metastasis and improve the clinical outcome of osteosarcoma patients.