The phosphodiesterase III inhibitor olprinone inhibits hippocampal glutamate release via a cGMP/PKG pathway

Chronic hyponatremia in a patient with renal salt wasting and without cerebral disease: relationship between RSW, risk of fractures and cognitive impairment

Renal salt wasting syndrome (RSW) is defined as a renal loss of sodium leading to hyponatremia and a decrease in extracellular fluid volume (ECV). Differentiation of this disorder from the syndrome of inappropriate antidiuretic hormone secretion (SIADH), a common cause of hyponatremia, can be difficult because both can present with hyponatremia and concentrated urine with natriuresis. Our clinical case about a 78-year-old woman with a recent fracture of the right femur not only confirms that this syndrome can occur in patients without intracranial pathologies (CT documented), but depicts how the hyponatremia caused by RSW can show a chronic, oscillating course. This is an interesting point of view because it suggests to us to consider RSW in the differential diagnosis of patients with chronic hyponatremia.

The cyclic AMP signaling pathway: Exploring targets for successful drug discovery (Review)

During development of disease, complex intracellular signaling pathways regulate an intricate series of events, including resistance to external toxins, the secretion of cytokines and the production of pathological phenomena. Adenosine 3′,5′-cyclic monophosphate (cAMP) is a nucleotide that acts as a key second messenger in numerous signal transduction pathways. cAMP regulates various cellular functions, including cell growth and differentiation, gene transcription and protein expression. This review aimed to provide an understanding of the effects of the cAMP signaling pathway and the associated factors on disease occurrence and development by examining the information from a new perspective. These novel insights aimed to promote the development of novel therapeutic approaches and aid in the development of new drugs.

Milrinone, a phosphodiesterase III inhibitor, prevents reduction of jugular bulb saturation during rewarming from hypothermic cardiopulmonary bypass

Introduction: Inadequate cerebral oxygen balance during cardiopulmonary bypass may cause neuropsychological dysfunction. Milrinone, a phosphodiesterase III inhibitor, augments cerebral blood flow by direct vasodilatation. We conducted a prospective, randomized study in patients undergoing cardiac surgery with cardiopulmonary bypass to clarify the clinical efficacy of milrinone in the imbalance of cerebral oxygen supply and demand during the rewarming period of cardiopulmonary bypass.

Methods: This is a prospective, randomized and placebo-controlled study. After anesthesia, a 5.5 F fiberoptic oximeter catheter was inserted into the right jugular bulb retrogradely for monitoring the jugular venous oxyhemoglobin saturation (SjO2). Patients were randomly assigned to two groups, one receiving a continuous infusion of milrinone, 0.5 µg/kg/min during hypothermic cardiopulmonary bypass, and the other receiving saline as control.

Results: Milrinone significantly prevented the reduction of the jugular venous oxyhemoglobin saturation at 10 minutes from the start of rewarming compared with the control group, but did not do so from 10 to 20 minutes after rewarming.

Conclusion: Milrinone suppresses the reduction of SjO2 and improves the balance of cerebral oxygen supply and demand during the early rewarming period of hypothermic cardiopulmonary bypass.

Effect of olprinone, a phosphodiesterase III inhibitor, on balance of cerebral oxygen supply and demand during cardiopulmonary bypass

Neuropsychological dysfunction with cardiopulmonary bypass (CPB) may be facilitated by inadequate cerebral oxygen balance during CPB. Olprinone, a phosphodiesterase III inhibitor, augments cerebral blood flow by a direct vasodilator effect on cerebral arteries. We conducted the present randomized study in patients undergoing cardiac surgery with CPB to investigate whether olprinone improved the balance of cerebral oxygen supply and demand during the rewarming period of CPB. After anesthesia, a 5.5 F fiberoptic oximeter catheter was inserted into the right jugular bulb retrogradely for monitoring the jugular venous oxyhemoglobin saturation (SjO2), and a probe of transcranial near-infrared spectroscopy was placed over the forehead for monitoring the bilateral regional cerebral oxygen saturation (rSO2). Patients were randomly assigned to 3 groups, and olprinone was administered at 0, 0.2, or 0.4 μg·kg(-1)·min(-1) after establishment of hypothermic CPB. Olprinone significantly prevented the reduction of the SjO2 at 5 and 10 minutes after the start of rewarming, although it did not alter rSO2. Furthermore, there was a minor reduction of the bilateral rSO2 at low doses of olprinone (0.2 μg·kg(-1)·min(-1)). We conclude that olprinone prevents the decrease of the SjO2 at the rewarming period and improves the balance of cerebral oxygen supply and demand during the rewarming period of CPB. In addition, a future extended study may be required to elucidate the effect of low dose of olprinone.

Natriuretic peptides in brain physiology

Natriuretic peptides (NPs) regulate salt and water homeostasis by inducing natriuresis and diuresis in the kidney. These actions in addition to those via the heart and vascular system play important roles in the regulation of blood pressure. In the central nervous system NPs play a significant role in neuronal development, synaptic transmission and neuroprotection. Currently, six different human NPs have been described: atrial natriuretic peptide (ANP), urodilatin (URO, renal natriuretic peptide), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) as well as guanylin and uroguanylin. ANP, URO and BNP activate the natriuretic peptide receptor A (NPR-A or guanylate cyclase A (GC-A)) while CNP activates natriuretic peptide receptor B (NPR-B or guanylate cyclase B (GC-B)). Guanylin and uroguanylin are known to activate guanylate cyclase C (GC-C). The receptors GC-A, GC-B, and GC-C are widely expressed in the human body. Currently, GC-B and CNP seems to have the highest expression in central nervous system compared to other NPs and their receptors. All known NPs generate intracellular cyclic GMP (cGMP) by activating their specific guanylate cyclase receptors. Subsequently, cGMP is able to activate protein kinase I or II (PKG I or II) and/or directly regulate transmembrane proteins such as ion channels, transporters and pumps. NPs also bind to the natriuretic peptide receptor C (also called clearance receptor NPR-C) which is a major pathway for the degradation of NPs and has no guanylate cyclase activity. In this review we will focus on new insights regarding the physiological effects of NPs in the brain, especially specific areas of their signaling pathways in neurons and glial cells.

Olprinone, a specific phosphodiesterase (PDE)-III inhibitor, reduces the development of multiple organ dysfunction syndrome in mice

Olprinone is a specific phosphodiesterase (PDE)-III inhibitor, which has been found to have anti-inflammatory effects in addition to its main inotropic and peripheral vasodilatory effects. In the present study we investigated the effects of olprinone (0.2mg/kg, i.p.) on the development of zymosan-induced multiple organ failure in mice. Treatment with olprinone attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan. Olprinone also attenuated the lung, liver and pancreatic injury, renal dysfunction as well as the increased lung and intestine myeloperoxidase (MPO) activity caused by zymosan. Immunohistochemical analysis for inducible nitric oxide synthase (iNOS), nitrotyrosine, poly(ADP-ribose) (PAR), tumor necrosis factor-α (TNF-α) and interleuchin-1β (IL-1β) revealed positive staining in pancreatic and intestinal tissue obtained from zymosan-injected mice. The degree of staining for nitrotyrosine, iNOS, PAR, TNF-α and IL-1β was markedly reduced in tissue sections obtained from zymosan-injected mice, which had received olprinone. In addition, administration of zymosan caused a severe illness in the mice characterized by significant loss of body weight and a 60% of mortality at the end of observation period (7 days). Treatment with olprinone significantly reduced the development of systemic toxicity, loss in body weight and mortality, caused by zymosan. This study provides evidence that olprinone attenuates the degree of zymosan-induced shock in mice.