The effects of RSR13 on microvascular Po2 kinetics and muscle contractile performance in the rat arterial ligation model of peripheral arterial disease

New potential treatment for cardiovascular disease through modulation of hemoglobin oxygen binding curve: Myo-inositol trispyrophosphate (ITPP), from cancer to cardiovascular disease

The human body is a highly aerobic organism, which needs large amount of oxygen, especially in tissues characterized by high metabolic demand, such as the heart. Inadequate oxygen delivery underlies cardiovascular diseases, such as coronary artery disease, heart failure and pulmonary hypertension. Hemoglobin, the oxygen-transport metalloprotein in the red blood cells, gives the blood enormous oxygen carrying capacity; thus oxygen binding to hemoglobin in the lungs and oxygen dissociation in the target tissues are crucial points for oxygen delivery as well as potential targets for intervention. Myo-inositol trispyrophosphate (ITPP) acts as an effector of hemoglobin, shifting the oxygen dissociation curve to the right and increasing oxygen release in the target tissues, especially under hypoxic conditions. ITPP has been successfully used in cancer studies, demonstrating anti-cancer properties due to prevention of tumor hypoxia. Currently it is being tested in phase 2 clinical trials in humans with various tumors. First preclinical evidence also indicates that it can successfully alleviate myocardial hypoxia and prevent adverse left ventricular and right ventricular remodeling in post-myocardial infarction heart failure and pulmonary hypertension. The aim of the article is to summarize the current knowledge on ITTP, as well as to determine the prospects for its potential use in the treatment of many cardiovascular disorders.

Vascular permeability of skeletal muscle microvessels in rat arterial ligation model: in vivo analysis using two-photon laser scanning microscopy

Peripheral artery disease (PAD) in the lower limb compromises oxygen supply due to arterial occlusion. Ischemic skeletal muscle is accompanied by capillary structural deformation. Therefore, using novel microscopy techniques, we tested the hypothesis that endothelial cell swelling temporally and quantitatively corresponds to enhanced microvascular permeability. Hindlimb ischemia was created in male Wistar rat's by iliac artery ligation (AL). The tibialis anterior (TA) muscle microcirculation was imaged using intravenously infused rhodamine B isothiocyanate dextran fluorescent dye via two-photon laser scanning microscopy (TPLSM) and dye extravasation at 3 and 7 days post-AL quantified to assess microvascular permeability. The TA microvascular endothelial ultrastructure was analyzed by transmission electron microscopy (TEM). Compared with control (0.40 ± 0.15 μm3 × 106), using TPLSM, the volumetrically determined interstitial leakage of fluorescent dye measured at 3 (3.0 ± 0.40 μm3 × 106) and 7 (2.5 ± 0.8 μm3 × 106) days was increased (both P < 0.05). Capillary wall thickness was also elevated at 3 (0.21 ± 0.06 μm) and 7 (0.21 ± 0.08 μm) days versus control (0.11 ± 0.03 μm, both P < 0.05). Capillary endothelial cell swelling was temporally and quantitatively associated with elevated vascular permeability in the AL model of PAD but these changes occurred in the absence of elevations in protein levels of vascular endothelial growth factor (VEGF) its receptor (VEGFR2 which decreased by AL-7 day) or matrix metalloproteinase. The temporal coherence of endothelial cell swelling and increased vascular permeability supports a common upstream mediator. TPLSM, in combination with TEM, provides a sensitive and spatially discrete technique to assess the mechanistic bases for, and efficacy of, therapeutic countermeasures to the pernicious sequelae of compromised peripheral arterial function.

Effects of clenbuterol administration on mitochondrial morphology and its regulatory proteins in rat skeletal muscle

Clenbuterol induces a slow-to-fast fiber type transition in skeletal muscle. This muscle fiber transition decreased mitochondrial oxidative capacity and respiratory function. We hypothesized that the clenbuterol-mediated reduction in oxidative capacity is associated with the alteration in mitochondrial morphology. To verify this hypothesis, we examined whether clenbuterol alters mitochondrial morphology and mitochondrial regulatory proteins in rat skeletal muscle. Clenbuterol was administered to rats via drinking water (30 mg/L) for 3 weeks. Myosin heavy chain (MHC) isoform composition, mitochondrial morphology, and fusion and fission regulatory protein levels in deep region and superficial region in tibialis anterior (TA) muscles were assessed. Clenbuterol induced the fiber type transition from slow to fast in both the regions of TA. The levels of optic atrophy protein 1, mitofusin 2, and mitochondrial fission 1, but not of dynamin-related protein 1, significantly decreased in deep and superficial muscles after clenbuterol administration (P < 0.01). Also, observation using the transmission electron microscopy showed a decrease in mitochondrial volume (P < 0.05) and an increase in proportion of continuous or interacting mitochondria across Z-lines (P < 0.05). We showed that clenbuterol administration induces a transition in the muscle fiber type composition toward fast phenotype and causes alterations in mitochondrial morphology with a concomitant decrease in mitochondrial fusion and fission regulatory protein levels. These mitochondrial morphological alterations may influence deleterious effects on skeletal muscle metabolism.