NO-independent stimulation or activation of soluble guanylyl cyclase during early reperfusion limits infarct size

Aims Guanylyl cyclase-cyclic guanosine monophosphate signalling plays an important role in endogenous cardioprotective signalling. The aim was to assess the potential of direct pharmacological activation and stimulation of soluble guanylyl cyclase, targeting different redox states of the enzyme, to limit myocardial necrosis during early reperfusion. Methods and results Rat isolated hearts were subjected to reversible left coronary artery occlusion (ischaemia-reperfusion) and infarct size was assessed by the tetrazolium staining technique. Administration during early reperfusion of BAY 41-2272, an NO-independent, haem-dependent stimulator of soluble guanylyl cyclase targeting the reduced state, or BAY 60-2770, an NO-independent, haem-independent activator targeting the oxidized state, significantly limited infarct size. Inhibition of NO synthesis did not abrogate this protection, but exogenous perfusion of NO with BAY 41-2272 produced a synergistic effect. The haem site oxidiser, ODQ abrogated the protection afforded by BAY 41-2272 but potentiated the protection afforded by BAY 60-2770. Targeting both the reduced and oxidized forms of sGC together did not afford additive protection. Conclusions Targeting either reduced or oxidized forms of sGC during early reperfusion affords cardioprotection, providing support for the concept that direct sGC manipulation at reperfusion has therapeutic potential for the management of acute myocardial infarction

Fluorescence Dequenching Makes Haem-Free Soluble Guanylate Cyclase Detectable in Living Cells

In cardiovascular disease, the protective NO/sGC/cGMP signalling-pathway is impaired due to a decreased pool of NO-sensitive haem-containing sGC accompanied by a reciprocal increase in NO-insensitive haem-free sGC. However, no direct method to detect cellular haem-free sGC other than its activation by the new therapeutic class of haem mimetics, such as BAY 58-2667, is available. Here we show that fluorescence dequenching, based on the interaction of the optical active prosthetic haem group and the attached biarsenical fluorophor FlAsH can be used to detect changes in cellular sGC haem status. The partly overlap of the emission spectrum of haem and FlAsH allows energy transfer from the fluorophore to the haem which reduces the intensity of FlAsH fluorescence. Loss of the prosthetic group, e.g. by oxidative stress or by replacement with the haem mimetic BAY 58-2667, prevented the energy transfer resulting in increased fluorescence. Haem loss was corroborated by an observed decrease in NO-induced sGC activity, reduced sGC protein levels, and an increased effect of BAY 58-2667. The use of a haem-free sGC mutant and a biarsenical dye that was not quenched by haem as controls further validated that the increase in fluorescence was due to the loss of the prosthetic haem group. The present approach is based on the cellular expression of an engineered sGC variant limiting is applicability to recombinant expression systems. Nevertheless, it allows to monitor sGC's redox regulation in living cells and future enhancements might be able to extend this approach to in vivo conditions

Current NAFLD guidelines for risk stratification in diabetic patients have poor diagnostic discrimination

Patients with type 2 diabetes (T2D) are at risk for non-alcoholic fatty liver disease (NAFLD) and associated complications. This study evaluated the performance of international (EASL-EASD-EASO) and national (DGVS) guidelines for NAFLD risk stratification. Patients with T2D prospectively underwent ultrasound, liver stiffness measurement (LSM) and serum-based fibrosis markers. Guideline-based risk classification and referral rates for different screening approaches were compared and the diagnostic properties of simplified algorithms, genetic markers and a new NASH surrogate (FAST score) were evaluated. NAFLD risk was present in 184 of 204 screened patients (age 64.2 ± 10.7 years; BMI 32.6 ± 7.6 kg/m2). EASL-EASD-EASO recommended specialist referral for 60–77% depending on the fibrosis score used, only 6% were classified as low risk. The DGVS algorithm required LSM for 76%; 25% were referred for specialised care. The sensitivities of the diagnostic pathways were 47–96%. A simplified referral strategy revealed a sensitivity/specificity of 46/88% for fibrosis risk. Application of the FAST score reduced the referral rate to 35%. This study (a) underlines the high prevalence of fibrosis risk in T2D, (b) demonstrates very high referral rates for in-depth hepatological work-up, and (c) indicates that simpler referral algorithms may produce comparably good results and could facilitate NAFLD screening

The multicomponent medication lymphomyosot improves the outcome of experimental lymphedema

Background: Secondary lymphedema is a life-long disease of painful tissue swelling that often follows axillary lymph node dissection to treat breast cancer. It is hypothesized that poor lymphatic regeneration across the obstructive scar tissue during the wound healing process may predispose the tissue to swell at a later date. Treatment for lymphedema remains suboptimal and is in most cases palliative. The purpose of this study was to evaluate the ability of Lymphomyosot to treat tissue swelling and promote lymphangiogenesis in experimental models of murine lymphedema. Methods: Experimental models of mouse lymphedema were injected with varied amounts of Lymphomyosot and saline as control. Measurements of tail swelling and wound closure were taken and compared amongst the groups. Three separate groups of mice were analyzed for lymphatic capillary migration, lymphatic vessel regeneration, and macrophage recruitment. Results: Lymphomyosot significantly reduced swelling and increased the rate of surgical wound closure. Lymphomyosot did not increase the migration of lymph capillaries in a mouse tail skin regeneration model or regeneration of lymph vessels following murine axillary lymph node dissection. Conclusions: Lymphomyosot may act through inflammatory and wound repair pathways to reduce experimental lymphedema. Its ability to regulate inflammation as well as assist in tissue repair and extracellular formation may allow for the production of a scar-free matrix bridge through which migrating cells and accumulated interstitial fluid can freely spread. © 2013, Mary Ann Liebert, Inc

NO-independent stimulation or activation of soluble guanylyl cyclase during early reperfusion limits infarct size

Aims Guanylyl cyclase-cyclic guanosine monophosphate signalling plays an important role in endogenous cardioprotective signalling. The aim was to assess the potential of direct pharmacological activation and stimulation of soluble guanylyl cyclase, targeting different redox states of the enzyme, to limit myocardial necrosis during early reperfusion. Methods and results Rat isolated hearts were subjected to reversible left coronary artery occlusion (ischaemia-reperfusion) and infarct size was assessed by the tetrazolium staining technique. Administration during early reperfusion of BAY 41-2272, an NO-independent, haem-dependent stimulator of soluble guanylyl cyclase targeting the reduced state, or BAY 60-2770, an NO-independent, haem-independent activator targeting the oxidized state, significantly limited infarct size. Inhibition of NO synthesis did not abrogate this protection, but exogenous perfusion of NO with BAY 41-2272 produced a synergistic effect. The haem site oxidiser, ODQ abrogated the protection afforded by BAY 41-2272 but potentiated the protection afforded by BAY 60-2770. Targeting both the reduced and oxidized forms of sGC together did not afford additive protection. Conclusions Targeting either reduced or oxidized forms of sGC during early reperfusion affords cardioprotection, providing support for the concept that direct sGC manipulation at reperfusion has therapeutic potential for the management of acute myocardial infarction