Biology subjects

Becher, S.

Publications and source records attributed to Becher, S..

4 recordsLinked to original sources

bioRxiv2024

Distinct effects of acute and chronic blood loss anemia on vascular function after acute myocardial infarction

BackgroundAnemia is frequently observed in patients with cardiovascular diseases (CVD). Anemia alone or in combination with other morbid conditions leads to poor prognosis in acute myocardial infarction (AMI). We recently showed that moderate blood loss anemia is associated with red blood cell (RBC) dysfunction and a compensatory increase in flow-mediated dilation (FMD) responses which are compromised in chronic blood loss anemia However, the effects of acute anemia (AA) and chronic anemia (CA) on endothelial function after AMI are unclear. In this study, we evaluated systemic endothelial function following AMI in established murine models of blood loss acute and chronic anemia. We hypothesize that both AA and CA aggravate systemic endothelial dysfunction (ED) after AMI. Methods and resultsAA or CA was induced in male C57BL/6J mice by repeated blood withdrawal for three consecutive days or six weeks, respectively. Separate groups of anemic and non-anemic mice underwent AMI via left anterior descending artery (LAD) ligation (45 min), followed by reperfusion. Endothelial function was assessed using both in vivo and in vitro methods 24 h post-AMI. Impaired flow-mediated dilation (FMD, in vivo) and endothelium-dependent relaxation (EDR) responses were observed in the aorta, femoral, and saphenous arteries of AA mice compared to their respective control groups 24 h post AMI. The aorta and saphenous arteries from CA mice showed significantly reduced vascular smooth muscle (VSM) contractile responses after AMI. Analysis of oxidative products of nitric oxide (NO) in plasma revealed reduced nitrite and nitrate levels in both AA and CA mice compared to controls 24 h post-AMI. Immunohistochemistry of aortic tissues from both anemic groups showed increased reactive oxygen species (ROS) product 4-Hydroxynonenal (4-HNE). Co-incubation of RBCs from anemic mice or anemic ST-elevation myocardial infarction (STEMI) patients with aortic rings from wild type mice demonstrated attenuated VSM contractile and EDR responses. Supplementation with the ROS scavenger N-acetyl cysteine (NAC) for four weeks improved both in vivo and ex vivo EDR in AA and CA mice 24 h post-AMI. ConclusionAfter AMI, both AA and CA are associated with severe ED, while VSM contractile responses specifically reduced in CA mice. These effects are accompanied by increased ROS and partly mediated by RBCs. Antioxidant supplementation with NAC is a potential therapeutic option to reverse the severe vascular dysfunction in anemia following AMI. Graphical AbstractDistinct effects of acute and chronic anemia on vascular function 24 h post-AMI. After acute myocardial infarction, acute and chronic anemia are associated with increased reactive oxygen species (ROS) and inflammation in endothelial cells (EC), leading to the inhibition of endothelial nitric oxide synthase (eNOS) and subsequent endothelial dysfunction by limiting NO bioavailability. Chronic anemia is additionally associated with decreased vascular smooth muscle cell (VSMC) function due to increased oxidative stress, leading to SMC dysfunction. After N-Acetyl-L-Cysteine (NAC) treatment, vascular function is improved in both anemic groups. O_FIG O_LINKSMALLFIG WIDTH=98 HEIGHT=200 SRC="FIGDIR/small/614629v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@136583aorg.highwire.dtl.DTLVardef@da8708org.highwire.dtl.DTLVardef@d73539org.highwire.dtl.DTLVardef@e7516a_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Novel fluorescence-based methods to determine infarct and scar size in murine models of reperfused myocardial infarction

BackgroundDetermination of infarct area and scar size following myocardial infarction (MI) is commonly used to evaluate the efficacy of potential cardioprotective treatments in mice and other animal models. MethodsFor both, early and late time points following MI, we compared classical histochemical approaches with fluorescence staining methods. Reperfused MI was induced in male C57BL/6J mice and hearts were extracted 24 hours, 7-, 21-, or 28-days following MI and stained with 2,3,5-Triphenyltetrazolium chloride (TTC) and Evans Blue, Hoechst, phalloidin, Sirius Red, Massons or Gomoris Trichrome or Wheat Germ Agglutinin (WGA). ResultsFluorescent staining combining Hoechst and phalloidin constitutes an alternative for TTC and Evans Blue, enabling a clear visualization of infarct area, area at risk, as well as remote area unaffected by MI. Infarct size early after reperfusion determined with TTC staining correlates strongly with that demarcated by phalloidin while combination of Hoechst and phalloidin staining can emulate classical TTC/Evans Blue staining 24 h post-MI. Moreover, WGA is equally accurate as the classical Sirius Red, Massons and Gomoris Trichrome stainings in identifying scar size in later phases (>7d) post-MI. Finally, we demonstrate feasibility of combining conventional fluorescence staining by localizing CD45+ leukocytes to specific regions of the infarcted myocardium. ConclusionWe established staining procedure is not inferior to classical TTC staining while providing substantial benefits including the option for unbiased software-assisted analysis while sparing ample residual tissue for additional analyses. Overall, this enhances the data quality and reduces the required animal numbers consistent with the 3R concept of animal experimentation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/604384v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@17ccc83org.highwire.dtl.DTLVardef@56d433org.highwire.dtl.DTLVardef@857f37org.highwire.dtl.DTLVardef@63297d_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2023

Inhibition of proline-rich-tyrosine kinase 2 restores cardioprotection by remote ischemic preconditioning in type 2 diabetes mellitus

BackgroundEndothelial function and cardioprotection through remote ischemic preconditioning (rIPC) are severely impaired in type 2 diabetes mellitus (T2DM). Proline-rich tyrosine kinase 2 (Pyk2), a downstream target of the insulin receptor, reduces endothelial nitric oxide synthase (eNOS) activity. Therapeutic options to rescue cardioprotection in T2DM and improve outcomes after acute myocardial infarction (AMI) are lacking. We hypothesized that vascular endothelium contributes to rIPC, and that inhibition of Pyk2 restores cardioprotection in T2DM through modulation of eNOS, thus limiting infarct size. MethodsNew Zealand Obese (NZO) mice were used as a polygenic model of T2DM. Effects of Pyk2-inhibition on endothelial function, remote ischemic preconditioning (rIPC), and infarct size (IS) after ischemia/reperfusion (I/R) were compared in NZO, eNOS KO, and C57Bl/6 (Bl6) mice. Plasma derived from mice and individuals with or without T2DM at baseline and after rIPC was transferred to isolated hearts and aortic rings to assess the effects of Pyk2-inhibition on remote tissue protection. ResultsTransfer experiments with plasma drawn from non-diabetic humans and mice exposed to rIPC demonstrate that endothelium-dependent signals for remote tissue protection are conveyed by plasma. Key features reflecting the glucometabolic spectrum in T2DM were detected in NZO mice, including hyperinsulinemia, insulin resistance, obesity, and impaired glucose tolerance. Similar to T2DM patients, these mice also revealed endothelial dysfunction with decreased flow-mediated dilation (FMD), reduced circulating nitrite levels, elevated arterial blood pressure, and larger infarct size after I/R. Pyk2 increased the phosphorylation of eNOS on its inhibitory site (Tyr656). Cardioprotective effects by rIPC were lost in NZO mice. Inhibition of Pyk2 restored endothelial function and rescued endothelium-dependent cardioprotection after rIPC displayed by lower IS and improved LV function post I/R. ConclusionEndothelial function contributing to remote tissue protection is severely impaired in diabetes mellitus. Proline-rich tyrosine kinase 2 is a novel target to rescue cardioprotection through endothelium-dependent remote ischemic preconditioning, advocating its role in limiting infarct size in diabetes mellitus. Clinical perspective What is new?O_LIVascular endothelium contributes to remote tissue protection in ischemic preconditioning, which is severely impaired in diabetes C_LIO_LIProline-rich tyrosine kinase 2 reduces eNOS-activity, causes endothelial dysfunction, and impairs cardioprotection through ischemic preconditioning C_LIO_LIInhibition of proline-rich tyrosine kinase 2 restores eNOS activity, endothelial function, and cardioprotective effects of remote ischemic preconditioning limiting infarct size in an experimental model of diabetes. C_LI What are the clinical implications?O_LIProper endothelial function is cirtical to maintain cardiovascular health. Endothelial dysfunction contributes to impaired remote tissue protection in diabetes. C_LIO_LIThese data demonstrate for the first time that endothelium-dependent cardioprotection in myocardial ischemia/reperfusion through remote ischemic preconditioning can be restored in diabetes. C_LIO_LIProline-rich tyrosine kinase 2 is a novel target to restore endothelium-dependent remote cardioprotection to improve the outcome of diabetic patients with acute myocardial infarction. C_LI

physiology↗

bioRxiv2020

The receptor-like cytoplasmic kinase MAZZA integrates CLAVATA-family receptor signaling to mediate stomatal patterning in Arabidopsis thaliana

The receptor-like kinases (RLKs) CLAVATA1 (CLV1) and BARELY ANY MERISTEMs (BAM1 - 3) form the CLV-family (CLVf), which perceives peptides of the CLV3/EMBRYO SURROUNDING REGION (ESR)-related (CLE) family within various signaling pathways of Arabidopsis thaliana. CLE peptide signaling, which is required for meristem size control, vascular development, or pathogen responses, involves the formation of receptor complexes at the plasma membrane (PM). These complexes comprise RLKs and co-receptors in varying compositions depending on the signaling context and regulate target gene expression, such as WUSCHEL (WUS). How the CLE signal is transmitted intracellularly after perception at the PM is not known. Here, we found that the membrane-associated receptor-like cytoplasmic kinase (RLCK) MAZZA (MAZ) MAZ and additional members of the Pti1-like protein family interact in vivo with CLVf receptors. MAZ, which is widely expressed throughout the plant, localizes to the PM via posttranslational palmitoylation potentially enabling stimulus-triggered protein re-localization. We identified a role for a CLV1/MAZ signaling module during stomatal and root development, and redundancy could potentially mask other phenotypes of maz-1 mutants. We propose that RLCKs such as MAZ mediate CLVf signaling in a variety of developmental contexts, paving the way towards understanding the intracellular processes after CLE peptide perception.

developmental biology↗