Synthetic Atrial Natriuretic Peptide Improves Systemic and Splanchnic Circulation and Has a Lung-Protective Effect During Endotoxemia in Pigs

Possible contribution of the neprilysin/ACE pathway to sepsis in mice

AIM

Omapatrilat is an antagonist of angiotensin-converting (ACE) and neprilysin-neuropeptidase (NEP) enzymes. The aim of our study is to show that omapatrilat may have beneficial effects as a treatment for polymicrobial sepsis.

MAIN METHODS

A cecal ligation and puncture (CLP) sepsis model was used to evaluate 10 and 20 mg/kg doses of omapatrilat in mice (n = 30) fasted for 12 h. The lungs were removed 12 h after CLP, and lung levels of cytokines (tumor necrosis factor-alpha [TNF-α], interleukin-6 [IL-6], NF-κB), iNOS and eNOS mRNA expression, GSH and MDA levels, and ACE and NEP activities were determined. Histopathological examinations were also performed.

KEY FINDINGS

Omapatrilat treatment provided a dose-dependent reduction in oxidative stress and inflammatory parameters in lung tissues. Omapatrilat administration decreased lung iNOS and eNOS mRNA levels at 20 mg/kg dose. Histopathological analysis revealed a decline in the thickening and edema areas in the alveolar septa in the Sepsis+OMA20 group.

SIGNIFICANCE

Omapatrilat, a dual ACE and NEP inhibitor, protected lung tissue from sepsis damage by reducing ACE and NEP activities, by decreasing the mRNA expression levels of pro-inflammatory cytokines (TNF-α, IL-6, and NF-κB), by suppressing leukocyte infiltration and edema, by restoring iNOS and eNOS levels, and by restoring SOD activity and GSH and MDA levels, thereby reducing oxidative stress.

Ideal target arterial pressure after control of bleeding in a rabbit model of severe traumatic hemorrhagic shock: results from volume loading-based fluid resuscitation

BACKGROUND

Previously reported ideal target mean arterial pressure (MAP) after control of bleeding in traumatic hemorrhagic shock (THS) requires further verification in more clinically related models. The authors explored this issue via gradient volume loading without vasopressor therapy. As certain volume loading can induce secretion of atrial natriuretic peptide (ANP), which has been shown to be protective, the authors also observed its potential role.

MATERIALS AND METHODS

Fifty male New Zealand rabbits were submitted to 1.5 h of uncontrolled THS (with another eight rabbits assigned to the sham group). After bleeding control, treated rabbits were randomly (n = 10, respectively) resuscitated with blood and Ringer lactate (1:2) to achieve target MAP of 50, 60, 70, 80, and 90 mm Hg within 1 h. During the following 2 h, they were resuscitated toward baseline MAP. Rabbits were observed until 7 h.

RESULTS

After resuscitation, infused fluid was lower and oxidative stress injury was milder in the 70 mm Hg group. Fluid volume loaded during the initial hour after hemostasis was negatively correlated with pH, oxygen saturation, and base excess at the end of resuscitation. It also correlated positively with proinflammatory responses in bronchoalveolar lavage fluid at 7 h and 7-h mortality. Moreover, after volume loading, the 80 mm Hg group showed significantly increased serum ANP level, which correlated with the expression of Akt protein in the jejunum at 7 h.

CONCLUSIONS

In rabbits the ideal target MAP during the initial resuscitation of severe THS after hemostasis was 70 mm Hg. ANP may have a critical role in gut protection.

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

Brain natriuretic peptide has vasodilatory properties and may thus increase splanchnic perfusion and oxygenation. We compared the effects of recombinant brain natriuretic peptide on gastric mucosal microvascular haemoglobin oxygenation (reflectance spectrophotometry) and systemic variables with those of equi-hypotensive doses of two other vasodilators (nitroglycerine and dihydralazine). Chronically instrumented, healthy dogs were randomly allocated to receive on different days, one of the three drugs (nitroglycerine and dihydralazine doses titrated to reduce mean arterial pressure by ∼20%). Brain natriuretic peptide significantly increased gastric mucosal microvascular haemoglobin oxygenation selectively, i.e. without concomitant haemodynamic effects. In contrast, the other vasodilators either did not increase gastric mucosal microvascular haemoglobin oxygenation at all (nitroglycerine), or did so only with marked increases in other systemic haemodynamic variables (dihydralazine). Our data suggest a potential role of recombinant brain natriuretic peptide selectively for increasing microvascular mucosal oxygenation. Studies are required to extend these findings to the clinical setting.