The differential effects of recombinant brain natriuretic peptide, nitroglycerine and dihydralazine on systemic oxygen delivery and gastric mucosal microvascular oxygenation in dogs

Therapeutic peptides: current applications and future directions

Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.

Identification of physiologic treatment targets with favourable haemodynamic consequences in heart failure with preserved ejection fraction

AIMS

Heart failure with preserved ejection fraction (HFpEF) is characterized by complex pathophysiology including an impaired diastolic reserve. We recently showed that milrinone favourably modifies filling pressures at rest and during exertion in HFpEF patients; however, the responsible mechanism is uncertain. The objective of this study was to develop a clearer understanding of the acutely modifiable physiologic parameters that may be targeted in HFpEF.

METHODS AND RESULTS

We conducted computer modelling simulations based on invasive haemodynamic assessments, by right heart catheterization, in HFpEF patients at baseline and in response to milrinone. Our aim was to develop a detailed understanding of the physiologic mechanisms, which accounted for the observed actions. The resultant circulatory model of HFpEF encompassed the left ventricular (LV) end-systolic and end-diastolic pressure-volume relations, together with stressed blood volume, heart rate, and arterial mechanics. To support the modelled action of milrinone, we conducted complementary LV conductance catheter and echocardiography studies in sheep to evaluate LV end-systolic and end-diastolic pressure-volume relations. In HFpEF patients, the acute haemodynamic effects of intravenous milrinone (n = 10) administration compared with placebo (n = 10) included significant reductions in right atrial pressure (7 ± 1 to 3 ± 1 mmHg, P < 0.001) and pulmonary capillary wedge pressure (13 ± 1 to 8 ± 1 mmHg, P < 0.001), while cardiac index increased (2.77 ± 0.19 to 3.15 ± 0.14 L/min/m² , P < 0.05), and mean arterial pressure remained unchanged (95 ± 2 to 93 ± 3 mmHg, P = not significant). Computer simulations showed that these haemodynamic effects were explained by a concomitant 31% reduction in stressed blood volume together with 44% increase in LV end-systolic elastance (LV E_es ). Individually, changes in these parameters were not sufficient to explain the haemodynamic effects of milrinone. In vivo studies conducted in sheep (n = 5) showed that milrinone reduced LV filling pressure (8.0 ± 0.8 to 2.7 ± 0.6 mmHg, P < 0.01) and increased LV E_es (0.96 ± 0.07 to 2.07 ± 0.49, P < 0.05), while no significant effect on LV stiffness was observed (0.038 ± 0.003 to 0.034 ± 0.008, P = not significant).

CONCLUSIONS

These data demonstrate that stressed blood volume in HFpEF represents a relevant physiologic target in HFpEF; however, concomitant modulation of other cardiovascular parameters including LV contractility may be required to achieve desirable haemodynamic effects.

Hypothalamic paraventricular nucleus stimulation reduces intestinal injury in rats with ulcerative colitis

AIM: To investigate the effect and mechanism of stimulation of the hypothalamic paraventricular nucleus with glutamate acid in rats with ulcerative colitis (UC).

METHODS: The rats were anesthetized with 10% chloral hydrate via abdominal injection and treated with an equal volume of TNBS + 50% ethanol enema, injected into the upper section of the anus with the tail facing up. Colonic damage scores were calculated after injecting a certain dose of glutamic acid into the paraventricular nucleus (PVN), and the effect of the nucleus tractus solitarius (NTS) and vagus nerve in alleviating UC injury through chemical stimulation of the PVN was observed in rats. Expression changes of C-myc, Apaf-1, caspase-3, interleukin (IL)-6, and IL-17 during the protection against UC injury through chemical stimulation of the PVN in rats were detected by Western blot. Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in colon tissues of rats were measured by colorimetric methods.

RESULTS: Chemical stimulation of the PVN significantly reduced UC in rats in a dose-dependent manner. The protective effects of the chemical stimulation of the PVN on rats with UC were eliminated after chemical damage to the PVN. After glutamate receptor antagonist kynurenic acid was injected into the PVN, the protective effects of the chemical stimulation of the PVN were eliminated in rats with UC. After AVP-Vl receptor antagonist ([Deamino-penl, val4, D-Arg8]-vasopressin) was injected into NTS or bilateral chemical damage to NTS, the protective effect of the chemical stimulation of PVN on UC was also eliminated. After chemical stimulation of the PVN, SOD activity increased, MDA content decreased, C-myc protein expression significantly increased, caspase-3 and Apaf-1 protein expression significantly decreased, and IL-6 and IL-17 expression decreased in colon tissues in rats with UC.

CONCLUSION: Chemical stimulation of the hypothalamic PVN provides a protective effect against UC injury in rats. Hypothalamic PVN, NTS and vagus nerve play key roles in this process.