Carbon monoxide reverses established pulmonary hypertension

Pulmonary arterial hypertension (PAH) is an incurable disease characterized by a progressive increase in pulmonary vascular resistance leading to right heart failure. Carbon monoxide (CO) has emerged as a potently protective, homeostatic molecule that prevents the development of vascular disorders when administered prophylactically. The data presented in this paper demonstrate that CO can also act as a therapeutic (i.e., where exposure to CO is initiated after pathology is established). In three rodent models of PAH, a 1 hour/day exposure to CO reverses established PAH and right ventricular hypertrophy, restoring right ventricular and pulmonary arterial pressures, as well as the pulmonary vascular architecture, to near normal. The ability of CO to reverse PAH requires functional endothelial nitric oxide synthase (eNOS/NOS3) and NO generation, as indicated by the inability of CO to reverse chronic hypoxia-induced PAH in eNOS-deficient (nos3−/−) mice versus wild-type mice. The restorative function of CO was associated with a simultaneous increase in apoptosis and decrease in cellular proliferation of vascular smooth muscle cells, which was regulated in part by the endothelial cells in the hypertrophied vessels. In conclusion, these data demonstrate that CO reverses established PAH dependent on NO generation supporting the use of CO clinically to treat pulmonary hypertension

A System to Control Intraluminal Pressure and Flow Rate in Isolated Blood Vessels in Vitro

This thesis introduces a system to control intraluminal pressure and flow rate in an isolated, cannulated blood vessel preparation in vitro. The thesis describes the design, construction and testing of the system. It also describes experiments conducted using the system to determine the response of cat pulmonary arteries to changes in luminal flow rate and the results from these experiments. Chapter one provides an introduction to the goals of this thesis and background information on the interaction of pressure and flow in blood vessels. It also contains a review of the methods, in vivo and in vitro, that have been used to study pressure/flow interactions. Chapter two describes the specifications of the design of a system to control pressure and flow independently. This includes a description of the existing experimental apparatus, the requirements the system had to fulfill and the limitations placed on the design. Also, several rejected ideas are presented, along with reasons for rejection. Chapter three describes the final design for the pressure/flow control system. It describes in detail the circuit designed to control pressure and the construction of the device. Chapter four describes the methods used in testing the system and the results of the tests. This includes a description of the system and tissue preparation and set-up and operation of the pressure/flow control system. It describes calibrations performed on the system to test accuracy of pressure and flow control and response characteristics under several conditions. Chapter five describes in detail the experimental protocol and the results obtained from the experiments. Chapter six discusses the results obtained from the experiments done using the pressure/flow control system as well as the overall performance of the system

Mechanisms of flow-induced responses in piglet isolated cerebral arteries

We examined the effect of changing both steady and pulsatile flow on piglet cerebral artery diameter. Cerebral arteries were mounted on glass cannulas and bathed in and perfused with heated physiologic saline solution (PSS). An electronic system controlled pressure and a syringe pump provided constant flows. To produce pulsatile flow a solenoid occluded the inflow tubing. Vessel diameter was measured with a video system. Flow was increased from 0 to 1.6 ml/min at 20 mm Hg and vessel diameter measured (F/D curves). Increasing flow at constant pressure resulted in constriction at low flows and dilation at higher ones. The F/D curves were repeated in the presence of nitro-L-arginine (NLA), nitro-L-arginine methyl ester (L-NAME), indomethacin (IND), 6-hydroxydopamine (6-OHDA), ryanodine (RYN), after perfusion with glutaraldehyde (GLU) and in PSS with Na\sp+ reduced or Ca\sp{2+} removed. In the presence of NLA, L-NAME, and RYN dilation was abolished; constriction was abolished when Na\sp+ was reduced or Ca\sp{2+} removed. IND and 6-OHDA had no effect while perfusion with GLU abolished all response to flow. These data indicate that while neither prostaglandins nor adrenergic innervation play a role in either response, nitric oxide (NO) mediates flow-induced dilation through intracellular Ca\sp{2+}, constriction is modulated by extracellular Na\sp+ and Ca\sp{2+} and both responses are due to deformation of endothelial cells. The effect of pulsatile flow was determined by increasing mean flow under pulsatile conditions and by changing from steady to pulsatile flow at each mean flow. Pulses were $\pm$4 mm Hg, frequency was 2 Hz. Next, either frequency or amplitude was increased (2 Hz to 4 Hz; $\pm$4 to $\pm$8 mm Hg). Each protocol was repeated in the presence of NLA and after GLU perfusion. Arteries dilated upon initiation of pulses but diameter did not change with increased mean flow. Arteries also dilated when both pulse amplitude and frequency increased. NLA diminished and GLU abolished dilation to pulsatile flow, increased frequency and increased amplitude, suggesting that dilation was due to changes in shear stress and was mediated by NO

Regulation of Smooth Muscle Cell Proliferation by NADPH Oxidases in Pulmonary Hypertension

Hyperproliferation of pulmonary arterial smooth muscle cells is a key component of vascular remodeling in the setting of pulmonary hypertension (PH). Numerous studies have explored factors governing the changes in smooth muscle cell phenotype that lead to the increased wall thickness, and have identified various potential candidates. A role for reactive oxygen species (ROS) has been well documented in PH. ROS can be generated from a variety of sources, including mitochondria, uncoupled nitric oxide synthase, xanthine oxidase, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. In this article, we will review recent data supporting a role for ROS generated from NADPH oxidases in promoting pulmonary arterial smooth muscle cell proliferation during PH