Increased CRF signalling in a ventral tegmental area-interpeduncular nucleus-medial habenula circuit induces anxiety during nicotine withdrawal

Increased anxiety is a predominant withdrawal symptom in abstinent smokers, yet the neuroanatomical and molecular bases underlying it are unclear. Here, we show that withdrawal-induced anxiety increases activity of neurons in the interpeduncular intermediate (IPI), a subregion of the interpeduncular nucleus (IPN). IPI activation during nicotine withdrawal was mediated by increased corticotropin releasing factor (CRF) receptor-1 expression and signaling, which modulated glutamatergic input from the medial habenula (MHb). Pharmacological blockade of IPN CRF1 receptors or optogenetic silencing of MHb input reduced IPI activation and alleviated withdrawal-induced anxiety; whereas IPN CRF infusion in mice increased anxiety. We identified a meso-interpeduncular circuit, consisting of ventral tegmental area (VTA) dopaminergic neurons projecting to the IPN, as a potential source of CRF. Knock-down of CRF synthesis in the VTA prevented IPI activation and anxiety during nicotine withdrawal. These data indicate that increased CRF receptor signaling within a VTA-IPN-MHb circuit triggers anxiety during nicotine withdrawal.

Enhanced stem cell migration mediated by VCAM-1/VLA-4 interaction improves cardiac function in virus-induced dilated cardiomyopathy

Endogenous circulation of bone marrow-derived cells (BMCs) was observed in patients with dilated cardiomyopathy (DCM) who showed cardiac upregulation of Vascular Cell Adhesion Protein-1 (VCAM-1). However, the underlying pathophysiology is currently unknown. Thus, we aimed to analyze circulation, migration and G-CSF-based mobilization of BMCs in a murine model of virus-induced DCM. Mice with coxsackievirus B3 (CVB3) induced DCM and healthy controls were analyzed regarding their myocardial homing factors by PCR. To determine cardiac VCAM-1 expression ELISA and immunohistochemistry were applied. Flow cytometry was performed to analyze BMCs. Cardiac diameters and function were evaluated by echocardiography before and 4 weeks after G-CSF treatment. In murine CVB3-induced DCM an increase of BMCs in peripheral blood and a decrease of BMCs in bone marrow was observed. We found an enhanced migration of Very Late Antigen-4 (VLA-4⁺) BMCs to the diseased heart overexpressing VCAM-1 and higher numbers of CD45⁻CD34⁻Sca-1⁺ and CD45⁻CD34⁻c-kit⁺ cells. Mobilization of BMCs by G-CSF boosted migration along the VCAM-1/VLA-4 axis and reduced apoptosis of cardiomyocytes. Significant improvement of cardiac function was detected by echocardiography in G-CSF-treated mice. Blocking VCAM-1 by a neutralizing antibody reduced the G-CSF-dependent effects on stem cell migration and cardiac function. This is the first study showing that in virus-induced DCM VCAM-1/VLA-4 interaction is crucial for recruitment of circulating BMCs leading to beneficial anti-apoptotic effects resulting in improved cardiac function after G-CSF-induced mobilization.

Antidiabetic gliptins in combination with G-CSF enhances myocardial function and survival after acute myocardial infarction

BACKGROUND

Medical stimulation of endogenous progenitor cell circulation may serve as a new therapeutic tool for treatment of acute myocardial infarction. We analyzed the effects of antidiabetic gliptins plus GCSF (granulocyte colony stimulating factor) on myocardial regeneration after myocardial infarction in a mouse model.

METHODS AND RESULTS

After surgical LAD-ligation (left anterior descending artery), Sitagliptin/Vildagliptin was applied yielding sufficient blood levels verified by mass spectrometry and significantly reducing activity of dipeptidyl peptidase (DPP) IV. GCSF or saline was administered intraperitoneally for 6 days. We assessed stem cell mobilization and homing (flow cytometry), infarct size (histology), neovascularization and cellular proliferation (immunohistology), heart function (Millar tip catheterization) and survival (Kaplan-Meier-curves). Gliptins±GCSF administration increased mobilization and cardiac homing of bone-marrow derived stem cells by stabilization of cardiac SDF1 (stromal cell-derived factor). For Sitagliptin, it could be shown that resident cardiac stem cells were stimulated, neovascularization was enhanced and cardiac remodeling was reduced. These effects finally improved myocardial function and increased survival for both gliptins. Although gliptins as a mono therapy lead to remarkable effects in a dose dependent manner and were superior to G-CSF mono-therapy, dual application of GCSF and gliptins revealed the best results. Since both gliptins yielded comparable effects concerning stem cell homing, cardiac function and survival, we suggest a class-effect of DPP-IV-inhibitors.

CONCLUSIONS

Thus, gliptins+GCSF and in high concentrations even as mono therapy have beneficial effects on cardiac regeneration after myocardial infarction beyond its anti-diabetic potential.

Dual stem cell therapy after myocardial infarction acts specifically by enhanced homing via the SDF-1/CXCR4 axis

BACKGROUND

G-CSF based stem cell mobilization and stabilization of cardiac SDF-1 by DPP-IV-inhibition (dual stem cell therapy) improve heart function and survival after myocardial infarction. However, it is barely understood whether this new approach acts specifically through the SDF-1/CXCR4 axis, stimulation of resident cardiac stem cells and improved myocardial perfusion. Therefore, we aimed to clarify the role of the SDF1/CXCR4 axis with respect to the benefits of a dual stem cell based therapy.

METHODOLOGY/PRINCIPAL FINDINGS

After surgically induced ligation of the LAD, SDF-1/CXCR4 interactions were specifically blocked by the CXCR4 receptor antagonist AMD3100 in G-CSF and Diprotin A treated C57BL/6 mice. G-CSF+DipA treated and non-treated animals served as controls. Because AMD3100 is known to mobilize bone marrow derived stem cells (BMCs) in high concentrations, the optimal dosage (1.25mg per kg body weight) sufficient to block CXCR4 without stimulating mobilization was established. AMD3100 treatment of G-CSF and Diprotin A stimulated mice significantly decreased myocardial homing of circulating stem cells (FACS analysis) and inverted the beneficial effects of (i) cardiac remodeling (histological analyses), (ii) heart function (Millar tip catheterization) and (iii) survival (Kaplan-Meier curves). G-CSF treatment in combination with DPP-IV inhibition enhanced neovascularization at the infarct border zone which was related to an improved myocardial blood flow as measured by SPECT. Moreover, dual stem cell treatment effectively stimulated the pool of resident cardiac stem cells (FACS) which was reversed by AMD3100 treatment.

CONCLUSIONS/SIGNIFICANCE

Our data give final proof that homing through the SDF-1/CXCR-4 axis is essential for the success of dual stem cell therapy.

Synergy between CD26/DPP-IV inhibition and G-CSF improves cardiac function after acute myocardial infarction

Ischemic cardiomyopathy is one of the main causes of death, which may be prevented by stem cell-based therapies. SDF-1alpha is the major chemokine attracting stem cells to the heart. Since SDF-1alpha is cleaved and inactivated by CD26/dipeptidylpeptidase IV (DPP-IV), we established a therapeutic concept--applicable to ischemic disorders in general--by combining genetic and pharmacologic inhibition of DPP-IV with G-CSF-mediated stem cell mobilization after myocardial infarction in mice. This approach leads to (1) decreased myocardial DPP-IV activity, (2) increased myocardial homing of circulating CXCR-4+ stem cells, (3) reduced cardiac remodeling, and (4) improved heart function and survival. Indeed, CD26 depletion promoted posttranslational stabilization of active SDF-1alpha in heart lysates and preserved the cardiac SDF-1-CXCR4 homing axis. Therefore, we propose pharmacological DPP-IV inhibition and G-CSF-based stem cell mobilization as a therapeutic concept for future stem cell trials after myocardial infarction.