Cyclooxygenase activity in bradykinin-induced dermal extravasation. A study in mice and humans

Contribution of cyclooxygenase-1-dependent prostacyclin synthesis to bradykinin-induced dermal extravasation

BACKGROUND

Non-allergic angioedema is a potentially life-threatening condition caused by accumulation of bradykinin and subsequent activation of bradykinin type 2 receptors (B2). Since COX activity plays a pivotal role in B2 signaling, the aim of this study was to determine which prostaglandins are the key mediators and which COX, COX-1 or COX-2, is predominantly involved.

METHODS

We used Miles assays to assess the effects of inhibitors of COX, 5-lipoxygenase, epoxyeicosatrienoic acid generation, cytosolic phospholipase A₂α and a variety of prostaglandin receptor antagonists on bradykinin-induced dermal extravasation in C57BL/6 and COX-1-deficient mice (COX-1^-/-). In addition, the prostacyclin metabolite 6-keto-PGF_1α was quantified by ELISA in subcutaneous tissue from C57BL/6 and human dermal microvascular endothelial cells. In the latter, 6-keto-PGF_1α was also quantified and identified by LC-MS/MS.

RESULTS

Unspecific COX inhibition by ibuprofen and diclofenac significantly reduced B2-mediated dermal extravasation in C57BL/6 but not COX-1^-/-. Likewise, inhibition of cytosolic phospholipase A₂α showed similar effects. Furthermore, extravasation in COX-1^-/- was generally lower than in C57BL/6. Of the prostaglandin antagonists used, only the prostacyclin receptor antagonist RO1138452 showed a significant reduction of dermal extravasation. Moreover, 6-keto-PGF_1α concentrations were increased after bradykinin treatment in subcutaneous tissue from C57BL/6 as well as in human dermal microvascular endothelial cells and this increase was abolished by diclofenac.

CONCLUSION

Our findings suggest that COX-1-dependent prostacyclin production is critically involved in dermal extravasation after activation of B2 in small dermal blood vessels. Targeting prostacyclin production and/or signaling appears to be a suitable option for acute treatment of non-allergic angioedema.

Reversal of SARS-CoV2-Induced Hypoxia by Nebulized Sodium Ibuprofenate in a Compassionate Use Program

INTRODUCTION

Sodium ibuprofenate in hypertonic saline (NaIHS) administered directly to the lungs by nebulization and inhalation has antibacterial and anti-inflammatory effects, with the potential to deliver these benefits to hypoxic patients. We describe a compassionate use program that offered this therapy to hospitalized COVID-19 patients.

METHODS

NaIHS (50 mg ibuprofen, tid) was provided in addition to standard of care (SOC) to hospitalized COVID-19 patients until oxygen saturation levels of > 94% were achieved on ambient air. Patients wore a containment hood to diminish aerosolization. Outcome data from participating patients treated at multiple hospitals in Argentina between April 4 and October 31, 2020, are summarized. Results were compared with a retrospective contemporaneous control (CC) group of hospitalized COVID-19 patients with SOC alone during the same time frame from a subset of participating hospitals from Córdoba and Buenos Aires.

RESULTS

The evolution of 383 patients treated with SOC + NaIHS [56 on mechanical ventilation (MV) at baseline] and 195 CC (21 on MV at baseline) are summarized. At baseline, NaIHS-treated patients had basal oxygen saturation of 90.7 ± 0.2% (74.3% were on supplemental oxygen at baseline) and a basal respiratory rate of 22.7 ± 0.3 breath/min. In the CC group, basal oxygen saturation was 92.6 ± 0.4% (52.1% were on oxygen supplementation at baseline) and respiratory rate was 19.3 ± 0.3 breath/min. Despite greater pulmonary compromise at baseline in the NaIHS-treated group, the length of treatment (LOT) was 9.1 ± 0.2 gs with an average length of stay (ALOS) of 11.5 ± 0.3 days, in comparison with an ALOS of 13.3 ± 0.9 days in the CC group. In patients on MV who received NaIHS, the ALOS was lower than in the CC group. In both NaIHS-treated groups, a rapid reversal of deterioration in oxygenation and NEWS2 scores was observed acutely after initiation of NaIHS therapy. No serious adverse events were considered related to ibuprofen therapy. Mortality was lower in both NaIHS groups compared with CC groups.

CONCLUSIONS

Treatment of COVID-19 pneumonitis with inhalational nebulized NaIHS was associated with rapid improvement in hypoxia and vital signs, with no serious adverse events attributed to therapy. Nebulized NaIHS s worthy of further study in randomized, placebo-controlled trials (ClinicalTrials.gov: NCT04382768).

Angioedema and Fatty Acids

Angioedema is a life-threatening emergency event that is associated with bradykinin and histamine-mediated cascades. Although bradykinin-mediated angioedema currently has specific therapeutic options, angioedema is sometimes intractable with current treatments, especially histamine-mediated angioedema, suggesting that some other mediators might contribute to the development of angioedema. Fatty acids are an essential fuel and cell component, and act as a mediator in physiological and pathological human diseases. Recent updates of studies revealed that these fatty acids are involved in vascular permeability and vasodilation, in addition to bradykinin and histamine-mediated reactions. This review summarizes each fatty acid’s function and the specific receptor signaling responses in blood vessels, and focuses on the possible pathogenetic role of fatty acids in angioedema.