Anesthesia effects on the low frequency blood flow oscillations in mouse skin

Skin Microhemodynamics and Mechanisms of Its Regulation in Type 2 Diabetes Mellitus

The review presents modern ideas about peripheral microhemodynamics, approaches to the ana-lysis of skin blood flow oscillations and their diagnostic significance. Disorders of skin microhemodynamics in type 2 diabetes mellitus (DM) and the possibility of their interpretation from the standpoint of external and internal interactions between systems of skin blood flow regulation, based on a comparison of couplings in normal and pathological conditions, including models of pathologies on animals, are considered. The factors and mechanisms of vasomotor regulation, among them receptors and signaling events in endothelial and smooth muscle cells considered as models of microvessels are discussed. Attention was drawn to the disturbance of Ca2+-dependent regulation of coupling between vascular cells and NO-dependent regulation of vasodilation in diabetes mellitus. The main mechanisms of insulin resistance in type 2 DM are considered to be a defect in the number of insulin receptors and impaired signal transduction from the receptor to phosphatidylinositol-3-kinase and downstream targets. Reactive oxygen species plays an important role in vascular dysfunction in hyperglycemia. It is assumed that the considered molecular and cellular mechanisms of microhemodynamics regulation are involved in the formation of skin blood flow oscillations. Parameters of skin blood microcirculation can be used as diagnostic and prognostic markers for assessing the state of the body.

Low-frequency oscillations of murine skin microcirculations and periodic changes of [Ca2+ ]i and [NO]i levels in murine endotheliocytes: An effect of provocative tests

The five frequency intervals of skin blood oscillation were described: cardiac, respiratory, myogenic, neurogenic, and endothelial. The endothelial interval is derived into NO-independent and NO-dependent. The exact molecular, cell, or systemic mechanisms of endothelial oscillations generation are unclear. We proposed that oscillations of Ca²⁺ and NO in endotheliocytes may be possible sources of skin blood perfusion (SBP) oscillations in endothelial interval. To examine our hypothesis we compared the oscillations of cytoplasmic Ca²⁺ and NO ([Ca²⁺ ]_i and [NO]_i ) concentration in cultured murine microvascular endotheliocytes and SBP oscillations in mice. Local heating test and model hypoxia were used as tools to evaluate an interconnection of studied parameters. [Ca²⁺ ]_i and [NO]_i were measured simultaneously by Fura-2 AM and DAF-FM. The SBP was measured by laser Doppler flowmetry. The [Ca²⁺ ]_i and [NO]_i oscillations at 0.005-0.01 Hz were observed in endotheliocytes, that coincides the ranges of NO-independent endothelial interval. Heating decreased amplitude of [Ca²⁺ ]_i and [NO]_i oscillations in cells in NO-independent endothelial interval, while amplitudes of SBP oscillations increased in NO-independent and NO-dependent intervals. Hypoxia reduced the [NO]_i oscillations amplitude. Heating test during hypoxia increased NO-independent endothelial SBP oscillations and decreased myogenic ones, did not effect on [NO]_i oscillations, and shifted [Ca²⁺ ]_i oscillations peak from 0.005-0.01 Hz to 0.01-0.018 Hz. We observed the [Ca²⁺ ]_i and [NO]_i oscillations synchronization within a cell and between cells for the first time. Heating abolished these synchronizations. Therefore low-frequency [Ca²⁺ ]_i and [NO]_i oscillations in endotheliocytes may be considered as modulators of low-frequency endothelial SBP oscillations.

Voluntary Oral Ingestion of a Sedative Prior to Euthanasia with CO2: Behavioural Responses of Mice

Laboratory mice are commonly euthanised with carbon dioxide (CO₂); however, there is ample evidence that this gas is aversive. Previous work suggests that sedation achieved via injection with benzodiazepines prior to CO₂ administration could reduce aversive behaviours during euthanasia. We explored the potential of using a voluntarily ingested sedative (tiletamine-zolazepam, Zoletil^®) prior to euthanasia. Male and female C57BL/6 mice were allocated into one of the five experimental groups, which differed in the dose of Zoletil: 0, 10, 20, 40, 80 or 100 mg/kg. A dose of 20 mg/kg was found to achieve mild sedation prior to euthanasia; mice which received this dose numerically reared and walked on the cage lid less, and showed ataxia, immobility and recumbency for longer than mice that received a lower dose. During euthanasia, mice that received 20 mg/kg showed fewer aversive responses to CO₂. Doses of 40 to 100 mg/kg were associated with signs of moderate to severe sedation, but resulted in an incomplete intake of the sedative, which made the interpretation of the aversiveness to CO₂ difficult. Voluntary oral administration of a sedative is an effective, affordable, and easy way to minimize the stress of mice to euthanasia with CO₂.

Oral Glucose Load and Human Cutaneous Microcirculation: An Insight into Flowmotion Assessed by Wavelet Transform

Simple Summary

There is increasing evidence to suggest that microcirculation becomes dysfunctional earlier than large blood vessels or the heart in several diseases. In diabetes mellitus, a disease characterized by chronic hyperglycemia, microvascular impairment is well-established; on the contrary, the effect of acute hyperglycemia in microcirculation remains unclarified. Our aim was to investigate the microvascular effect of an oral glucose load (OGL) using laser Doppler flowmetry (LDF) as a perfusion quantification technique, coupled with wavelet transform (WT) to perform a spectral decomposition of the LDF signal. On two distinct occasions (pre-load and post-load), sixteen healthy subjects drank either a standard glucose solution or water. Perfusion was assessed by LDF and WT while resting and during post-occlusive reactive hyperemia (PORH), evoked by a transient three-min occlusion of the brachial artery, in the forearm and the finger pulp. The OGL affected microcirculation in both sites compared to water, significantly blunting the PORH response in the forearm. The WT revealed significant differences in the cardiac and sympathetic components after OGL between the pre-load and post-load periods. These results suggest that an OGL induces a short-term subtle microvascular impairment, probably involving a modulation of the sympathetic nervous system.

Abstract

Microcirculation in vivo has been assessed using non-invasive technologies such as laser Doppler flowmetry (LDF). In contrast to chronic hyperglycemia, known to induce microvascular dysfunction, the effects of short-term elevations in blood glucose on microcirculation are controversial. We aimed to assess the impact of an oral glucose load (OGL) on the cutaneous microcirculation of healthy subjects, quantified by LDF and coupled with wavelet transform (WT) as an interpretation tool. On two separate occasions, sixteen subjects drank either a glucose solution (75 g in 250 mL water) or water (equal volume). LDF signals were obtained in two anatomical sites (forearm and finger pulp) before and after each load (pre-load and post-load, respectively), in resting conditions and during post-occlusive reactive hyperemia (PORH). The WT allowed decomposition of the LDF signals into their spectral components (cardiac, respiratory, myogenic, sympathetic, endothelial NO-dependent). The OGL blunted the PORH response in the forearm, which was not observed with the water load. Significant differences were found for the cardiac and sympathetic components in the glucose and water groups between the pre-load and post-load periods. These results suggest that an OGL induces a short-term subtle microvascular impairment, probably involving a modulation of the sympathetic nervous system.

Effect of the Non-Immunosuppressive MPT Pore Inhibitor Alisporivir on the Functioning of Heart Mitochondria in Dystrophin-Deficient mdx Mice

Supporting mitochondrial function is one of the therapeutic strategies that improve the functioning of skeletal muscle in Duchenne muscular dystrophy (DMD). In this work, we studied the effect of a non-immunosuppressive inhibitor of mitochondrial permeability transition pore (MPTP) alisporivir (5 mg/kg/day), reducing the intensity of the necrotic process and inflammation in skeletal muscles on the cardiac phenotype of dystrophin-deficient mdx mice. We found that the heart mitochondria of mdx mice show an increase in the intensity of oxidative phosphorylation and an increase in the resistance of organelles to the MPT pore opening. Alisporivir had no significant effect on the hyperfunctionalization of the heart mitochondria of mdx mice, and the state of the heart mitochondria of wild-type animals did not affect the dynamics of organelles but significantly suppressed mitochondrial biogenesis and reduced the amount of mtDNA in the heart muscle. Moreover, alisporivir suppressed mitochondrial biogenesis in the heart of wild-type mice. Alisporivir treatment resulted in a decrease in heart weight in mdx mice, which was associated with a significant modification of the transmission of excitation in the heart. The latter was also noted in the case of WT mice treated with alisporivir. The paper discusses the prospects for using alisporivir to correct the function of heart mitochondria in DMD.

Effect of the MPT Pore Inhibitor Alisporivir on the Development of Mitochondrial Dysfunction in the Heart Tissue of Diabetic Mice

Simple Summary

Diabetes mellitus as a systemic metabolic disease is one of the most serious threats to global health in this century. Diabetic cardiomyopathy is increasingly recognized as one of the most important complications of the disease, which is associated with impaired cell energy metabolism and damage to mitochondria in cardiomyocytes. Therefore, targeting mitochondrial dysfunction by pharmacological agents can be used as a therapeutic strategy in diabetic heart disease. The aim of the work was to study the effect of the mitochondria-targeted agent alisporivir on the development of mitochondrial dysfunction in the heart of mice with experimental diabetes mellitus. Alisporivir has been recently identified as a non-immunosuppressive analogue of cyclosporin A, a selective inhibitor of cyclophilin D and the mitochondrial permeability transition pore opening, with a potential in a wide range of therapeutic indications. Our results indicated that alisporivir alleviates diabetes-induced abnormalities in the ultrastructure and functions of mitochondria in cardiomyocytes and increases the rate of glucose utilization in diabetic mice. The data suggest that alisporivir acts as a mitochondria-targeted metabolic reprogramming agent and attenuates oxidative damage to the heart tissue of diabetic mice.

Abstract

Diabetes mellitus is a systemic metabolic disorder associated with mitochondrial dysfunction, with the mitochondrial permeability transition (MPT) pore opening being considered as one of its possible mechanisms. The effect of alisporivir, a non-immunosuppressive cyclosporin derivative and a selective inhibitor of the MPT pore opening, on the ultrastructure and functions of the heart mitochondria of mice with diabetes mellitus induced by a high-fat diet combined with streptozotocin injections was studied. The treatment of diabetic animals with alisporivir (2.5 mg/kg ip for 20 days) increased the rate of glucose clearance during the glucose tolerance test. The blood glucose level and the indicator of heart rate in alisporivir-treated diabetic mice tended to restore. An electron microscopy analysis showed that alisporivir prevented mitochondrial swelling and ultrastructural alterations in cardiomyocytes of diabetic mice. Alisporivir canceled the diabetes-induced increases in the susceptibility of heart mitochondria to the MPT pore opening and the level of lipid peroxidation products, but it did not affect the decline in mitochondrial oxidative phosphorylation capacity. The mRNA expression levels of Pink1 and Parkin in the heart tissue of alisporivir-treated diabetic mice were elevated, suggesting the stimulation of mitophagy. In parallel, alisporivir decreased the level of mtDNA in the heart tissue. These findings suggest that targeting the MPT pore opening by alisporivir alleviates the development of mitochondrial dysfunction in the diabetic heart. The cardioprotective effect of the drug in diabetes can be mediated by the induction of mitophagy and the inhibition of lipid peroxidation in the organelles.

Characterizing Vascular Dysfunction in Genetically Modified Mice through the Hyperoxia Model

Modelling is essential for a better understanding of microcirculatory pathophysiology. In this study we tested our hyperoxia-mouse model with healthy and non-healthy mice. Animals (n = 41) were divided in groups—a control group, with 8 C57/BL6 non-transgenic male mice, a diabetic group (DB), with 8 C57BLKsJ-db/db obese diabetic mice and the corresponding internal controls of 8 age-matched C57BLKsJ-db/+ mice, and a cardiac hypertrophy group (CH), with 9 FVB/NJ cα-MHC-NHE-1 transgenic mice prone to develop cardiac failure and 8 age-matched internal controls. After anesthesia, perfusion data was collected by laser Doppler flowmetry (LDF) during rest (Phase 1), hyperoxia (Phase 2), and recovery (Phase 3) and compared. The LDF wavelet transform components analysis (WA) has shown that cardiorespiratory, myogenic, and endothelial components acted as main markers. In DB group, db/+ animals behave as the Control group, but WA already demonstrated significant differences for myogenic and endothelial components. Noteworthy was the increase of the sympathetic components in the db/db set, as in the cardiac overexpressing NHE1 transgenic animals, reported as a main component of these pathophysiological processes. Our model confirms that flow motion has a universal nature. The LDF component’s WA provides a deeper look into vascular pathophysiology reinforcing the model’s reproducibility, robustness, and discriminative capacities.