Acute inhibition of nicotinamide adenine dinucleotide phosphate oxidase in the commissural nucleus of the solitary tract reduces arterial pressure and renal sympathetic nerve activity in renovascular hypertension.

BACKGROUND: A growing body of evidence suggests that oxidative stress plays a role in the pathophysiology of hypertension. However, the involvement of the reactive oxygen species (ROS) in the commissural nucleus of the solitary tract (commNTS) in development the of hypertension remains unclear. METHOD: We evaluated the hemodynamic and sympathetic responses to acute inhibition of NADPH oxidase in the commNTS in renovascular hypertensive rats. Under anesthesia, male Holtzman rats were implanted with a silver clip around the left renal artery to induce 2-kidney 1-clip (2K1C) hypertension. After six weeks, these rats were anesthetized and instrumented for recording mean arterial pressure (MAP), renal blood flow (RBF), renal vascular resistance (RVR), and renal sympathetic nerve activity (RSNA) during baseline and after injection of apocynin (nicotinamide adenine dinucleotide phosphate oxidase inhibitor), NSC 23766 (RAC inhibitor) or saline into the commNTS. RESULTS: Apocynin into the commNTS decreased MAP, RSNA, and RVR in 2K1C rats. NSC 23766 into the commNTS decreased MAP and RSNA, without changing RVR in 2K1C rats. CONCLUSION: These results demonstrate that the formation of ROS in the commNTS is important to maintain sympathoexcitation and hypertension in 2K1C rats and suggest that NADPH oxidase in the commNTS could be a potential target for therapeutics in renovascular hypertension.

Preclinical pharmacokinetics of a promising antineoplastic prototype piperazine-containing compound (LQFM018) in rats by a new LC-MS/MS bioanalytical method.

LQFM018 is a novel antineoplastic prototype, showing an expressive drug-triggered K562 leukemic cells death mechanism, through necroptotic signaling. Due to its promising effect, this study aimed to evaluate the pharmacokinetics of LQFM018 in rats, using a new validated bioanalytical LC-MS/MS-based method. Chromatographic column was an ACE® C18 (100 mm × 4.6 mm, 5 µm) eluted by a mobile phase composed of ammonium acetate 2 mM and formic acid 0.025%:methanol (50:50, v/v), under flow of 1.2 mL/min and injection volume of 3.0 µL. LQFM018 was extracted from rat plasma by a simple liquid-liquid method, using MTBE solvent. Rats were administered intraperitoneally at LQFM018 100 mg/kg dose and blood samples were collect at times of 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 h. Bioanalytical-LC-MS/MS-based method was rapid, high throughput and sensitive with a good linearity ranging from 10 (LLOQ) to 15000 ng/mL, besides precise and accurate, ranging of 0.8-7.3% and 96.8-107.6%, respectively. The prototype LQFM018 was rapid and well absorbed, and highly distributed, apparently due to its high lipid solubility. These features are primordial for an anticancer agent in the treatment of deep tumors, such as bone marrow neoplasms, in which the drug might permeate easily tissue barriers. Also, LQFM018 has demonstrated a high clearance, according to a low t1/2in rats, indicating a relative fast elimination phase related to a possible intense hepatic biotransformation. These information support further studies to establish new understands on pharmacokinetics of promising antineoplastic prototype LQFM018 from preclinical and clinical evaluations.

Dietary Nitrate Reduces Blood Pressure in Rats With Angiotensin II-Induced Hypertension via Mechanisms That Involve Reduction of Sympathetic Hyperactivity.

Several experimental and clinical studies have shown that dietary nitrate supplementation can increase nitric oxide bioavailability. In the oral cavity, commensal bacteria reduce nitrate to nitrite, which is subsequently absorbed into the circulation where reduction to nitric oxide by enzymatic systems occur. Although it is well-known that boosting the nitrate-nitrite-nitric oxide pathway can improve cardiovascular, renal, and metabolic functions and that sympathoexcitation contributes to the development of the same disorders, the potential effects of dietary nitrate on sympathetic activity remain to be elucidated. In this study, we hypothesized that treatment with inorganic nitrate could prevent the increase in sympathetic nerve activity in an experimental model of Ang II (angiotensin II)-induced hypertension. Multiple in vivo approaches were combined, that is, Wistar rats orally treated with the nitric oxide synthase inhibitor L-NAME (N(G)-nitro-L-arginine methyl ester, 0.5 g/L) and implanted with subcutaneous osmotic minipump for continuous delivery of Ang II (120 ng/kg per minute; 14 days). Simultaneously, rats were supplemented with sodium nitrate (10 mmol/L) or placebo (sodium chloride; 10 mmol/L) in the drinking water. Blood pressure, heart rate, and renal sympathetic nerve activity were recorded. In placebo-treated rats, Ang II+L-NAME treatment-induced arterial hypertension, which was linked with reduced spontaneous baroreflex sensitivity and increased renal sympathetic nerve activity, as well as upregulation of AT1Rs (Ang II type-1 receptors) in the rostral ventrolateral medulla. Supplementation with nitrate normalized the expression of AT1Rs in rostral ventrolateral medulla and reduced sympathetic nerve activity, which was associated with attenuated development of hypertension. In conclusion, chronic dietary nitrate supplementation blunted the development of hypertension via mechanisms that involve reduction of sympathetic outflow.

Blockade of Rostral Ventrolateral Medulla (RVLM) Bombesin Receptor Type 1 Decreases Blood Pressure and Sympathetic Activity in Anesthetized Spontaneously Hypertensive Rats.

Intrathecal injection of bombesin (BBS) promoted hypertensive and sympathoexcitatory effects in normotensive (NT) rats. However, the involvement of rostral ventrolateral medulla (RVLM) in these responses is still unclear. In the present study, we investigated: (1) the effects of BBS injected bilaterally into RVLM on cardiorespiratory and sympathetic activity in NT and spontaneously hypertensive rats (SHR); (2) the contribution of RVLM BBS type 1 receptors (BB1) to the maintenance of hypertension in SHR. Urethane-anesthetized rats (1.2 g · kg(-1), i.v.) were instrumented to record mean arterial pressure (MAP), diaphragm (DIA) motor, and renal sympathetic nerve activity (RSNA). In NT rats and SHR, BBS (0.3 mM) nanoinjected into RVLM increased MAP (33.9 ± 6.6 and 37.1 ± 4.5 mmHg, respectively; p < 0.05) and RSNA (97.8 ± 12.9 and 84.5 ± 18.1%, respectively; p < 0.05). In SHR, BBS also increased DIA burst amplitude (115.3 ± 22.7%; p < 0.05). BB1 receptors antagonist (BIM-23127; 3 mM) reduced MAP (-19.9 ± 4.4 mmHg; p < 0.05) and RSNA (-17.7 ± 3.8%; p < 0.05) in SHR, but not in NT rats (-2.5 ± 2.8 mmHg; -2.7 ± 5.6%, respectively). These results show that BBS can evoke sympathoexcitatory and pressor responses by activating RVLM BB1 receptors. This pathway might be involved in the maintenance of high levels of arterial blood pressure in SHR.