Mitochondrial bioenergetics, mass, and morphology are altered in cells of the degenerating human annulus.

Back pain and intervertebral disc degeneration have a growing socioeconomic healthcare impact. Information on mitochondrial function in human intervertebral disc cells, however, is surprisingly sparse. We assessed mitochondrial bioenergetics, mass, and ultrastructure in annulus cells cultured from human discs of varying degenerative stages. Citrate synthase activity (reflecting mitochondrial mass) declined significantly with increasing Thompson grade (p < 0.0001). Both mitochondrial (p = 0.009) and non-mitochondrial (p = 0.0029) respiration showed significant changes with increasing stages of disc degeneration. No significant relationships were found for the association of respiration data with herniated or non-herniated status, or with subject age. Examination of mitochondrial ultrastructure in cultured annulus cells revealed unusual features which included mitochondrial inclusion bodies, poorly defined cristae and dark staining. Findings reported here are novel and document biochemical, metabolic, and morphologic abnormalities in mitochondria in cells from more degenerated annulus cells. Data suggest that the disc degenerative, not age, is a major factor associated with mitochondrial impairment, and also implicate oxidative stress, driven by mitochondrial dysfunction, as a major component within the degenerating disc. Findings have relevance to advancements in cell-based therapies to treat disc degeneration.

A soluble guanylate cyclase stimulator, BAY 41-8543, preserves right ventricular function in experimental pulmonary embolism.

Pulmonary embolism (PE) increases pulmonary vascular resistance, causing right ventricular (RV) dysfunction, and poor clinical outcome. Present studies test if the soluble guanylate cyclase stimulator BAY 41-8543 reduces pulmonary vascular resistance and protects RV function. Experimental PE was induced in anesthetized, male Sprague-Dawley rats by infusing 25 µm polystyrene microspheres (1.95 million/100 g body wt, right jugular vein) producing moderate PE. Pulmonary artery vascular resistance, estimated as RVPSP/CO, increased 3-fold after 5 h of PE. Treatment with BAY 41-8543 (50 µg/kg, I.V.; given at the time of PE induction) normalized this index by reducing RVPSP and markedly increasing CO, via preservation of heart rate and stroke volume. Ex vivo RV heart function showed minimal changes at 5 h of PE, but decreased significantly after 18 h of PE, including peak systolic pressure (PSP, Control 39 ± 1 mmHg vs. 19 ± 3 PE), +dP/dt (1192 ± 93 mmHg/s vs. 444 ± 64) and -dP/dt (-576 ± 60 mmHg/s vs. -278 ± 40). BAY 41-8543 significantly improved all three indices of RV heart function (PSP 35 ± 3.5, +dP/dt 1129 ± 100, -dP/dt -568 ± 87). Experimental PE produced increased PVR and RV dysfunction, which were ameliorated by treatment with BAY 41-8543. Thus, there is vasodilator reserve in this model of experimental PE that can be exploited to reduce the stress upon the heart and preserve RV contractile function.

Pulmonary vascular reserve during experimental pulmonary embolism: effects of a soluble guanylate cyclase stimulator, BAY 41-8543.

OBJECTIVES: Pulmonary embolism causes pulmonary hypertension by mechanical obstruction and vasoconstriction. Therapeutic potential of pharmacologic dilation of unblocked vessels has received limited attention. We tested pulmonary vasodilator reserve using a soluble guanylate cyclase stimulator, BAY 41-8543. DESIGN: Controlled animal study. SETTING: Medical center research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Pulmonary embolism was induced by infusing 25-µm plastic microspheres in the right jugular vein, producing mild or moderate pulmonary hypertension. Control animals with no pulmonary embolism received suspension medium for microspheres. MEASUREMENTS AND MAIN RESULTS: Mild pulmonary embolism increased right ventricular peak systolic pressure (from 28 to 38 mm Hg) and decreased cardiac output (from 46 to 34 mL/min) with no change in mean arterial pressure. Infusion of BAY 41-8543 (50-200 µg/kg) decreased right ventricular peak systolic pressure. Five hrs moderate pulmonary embolism increased right ventricular peak systolic pressure (from 28 to 47 mm Hg) and decreased cardiac output (from 48 to 27 mL/min), causing right ventricular peak systolic pressure/cardiac output to increase from 0.6 control with no pulmonary embolism to 1.8 mm Hg/mL/min in 5-hr moderate pulmonary embolism + solvent for BAY 41-8543. Treatment of 5-hr moderate pulmonary embolism with BAY 41-8543 (50 µg/kg) caused a 2.2-fold increase in cardiac output (59 mL/min) with a 46% reduction in right ventricular peak systolic pressure (38 mm Hg), suggesting significant pulmonary vasodilation. Moderate pulmonary embolism decreased arterial sO2 (from 83% to 71%) and increased lactate (from 0.5 to 2.3 mmol/L). Treatment with BAY 41-8543 normalized sO2 and lactate. Hemolysis occurred during moderate experimental pulmonary embolism (60-fold increase in plasma hemoglobin). Treatment with BAY 41-8543 reduced free plasma hemoglobin content by 80%. CONCLUSIONS: In the setting of moderate impervious pulmonary embolism, treatment with a guanylate cyclase stimulator normalized pulmonary hemodynamics, reduced hemolysis, and improved oxygenation. These data support the hypothesis that pharmacologic dilation of nonobstructed pulmonary vasculature can effectively treat acute pulmonary hypertension from pulmonary embolism.

Up-regulation of arginase II contributes to pulmonary vascular endothelial cell dysfunction during experimental pulmonary embolism.

Pulmonary embolism (PE) causes pulmonary hypertension by mechanical obstruction and constriction of non-obstructed vasculature. We tested if experimental PE impairs pulmonary vascular endothelium-dependent dilation via activation of arginase II. Experimental PE was induced in male Sprague-Dawley rats by infusing 25 µm microspheres in the right jugular vein, producing moderate pulmonary hypertension. Shams received vehicle injection. Pulmonary arterial rings were isolated after 18 h and isometric tensions were determined. Dilations were induced with acetylcholine, calcium ionophore A23187 or nitroglycerin (NTG) in pre-contracted rings (phenylephrine). Protein expression was assessed by Western blot and immunohistochemistry. Arginase activity was inhibited by intravenous infusion of N(w)-hydroxy-nor-l-arginine (nor-NOHA). l-Arginine supplementation was also given. Endothelium-dependent dilation responses were significantly reduced in PE vs. vehicle-treated animals (ACh: 50 ± 9% vs. 93 ± 3%; A23187: 19 ± 7% vs. 85 ± 7%, p < 0.05), while endothelium-independent dilations (NTG) were unchanged. Endothelial nitric oxide synthase (eNOS) protein content was unchanged by PE. Expression of arginase II increased 4.5-fold and immunohistochemistry revealed increased arginase II staining. Nor-NOHA treatment and l-arginine supplementation significantly improved pulmonary artery ring endothelium-dependent dilation in PE (ACh: 58 ± 6% PE, 88 ± 6% PE + nor-NOHA, 84 ± 4% PE + l-arginine). Experimental PE impairs endothelium-dependent pulmonary artery dilation, while endothelium-independent dilation remains unchanged. The data support the conclusion that up-regulation of arginase II protein expression contributes to pulmonary artery endothelial dysfunction in this model of experimental PE.

Hyperbaric oxygen does not prevent neurologic sequelae after carbon monoxide poisoning.

UNLABELLED: Delayed neurologic sequelae occur in up to 40% of severe carbon monoxide (CO) poisonings. Conflicting clinical data support the efficacy of hyperbaric oxygen (HBO) therapy in the acute treatment of CO poisoning. OBJECTIVE: To determine whether oxygen therapy reduces neurologic sequelae after CO poisoning in mice. METHODS: Male Swiss-Webster mice were exposed to CO at 1,000 ppm for 40 minutes and then 50,000 ppm until loss of consciousness (LOC) (4-9 additional minutes). Total time of both phases of CO exposure was 40-49 minutes. Treatment included HBO with 3 atmospheres (ATA) 100% oxygen, normobaric oxygen (NBO) with 1 ATA 100% oxygen, or ambient air 15 minutes after LOC. All animals underwent passive avoidance training and memory was assessed by measuring step-down latency (SDL) and step-up latency (SUL) seven days following CO exposure. RESULTS: Carbon monoxide poisoning induced significant memory deficits (SDL(CO) = 156 sec; SUL(CO) = 75%) compared with nonpoisoned (NP) animals (SDL(NP) = 272 sec; SUL(NP) = 100%). Both HBO and NBO did not prevent these neurologic sequelae. Furthermore, no significant neurobehavioral differences were found between HBO and NBO. Histologic examination of the CA1 layer of the hippocampus for pyknotic cells showed significant damage from CO in the air-treated animals (9.6%) but not in the nonpoisoned animals (3.8%). No significant neuroprotection was seen histologically with NBO and HBO compared with ambient air. CONCLUSIONS: These results suggest that HBO is not effective in preventing neurologic sequelae in mice and that there is no benefit of HBO over NBO following severe CO neurotoxicity.