N(G)-nitro-L-arginine methyl ester, but not methylene blue, attenuates anaphylactic hypotension in anesthetized mice

Effect of Nitric Oxide Pathway Inhibition on the Evolution of Anaphylactic Shock in Animal Models: A Systematic Review

Simple Summary

Anaphylactic shock (AS) is the most serious consequence of anaphylaxis, with life-threatening sequelae including hypovolemia, shock, and arrhythmias. The literature lacks evidence for the effectiveness of interventions other than epinephrine in the acute phase of anaphylaxis. Our objective was to assess, through a systematic review, how inhibition of nitric oxide (NO) pathways affects blood pressure, and whether such blockade improves survival in AS animal models. AS was induced in all included studies after or before drug administration that targeted blockade of the NO pathway. In all animal species studied, the induction of AS caused a reduction in arterial blood pressure. However, the results show different responses to the inhibition of nitric oxide pathways. Overall, seven of fourteen studies using inhibition of nitric oxide pathways as pre-treatment before induction of AS showed improvement of survival and/or blood pressure. Four post-treatment studies from eight also showed positive outcomes. This review did not find strong evidence to propose modulation of blockade of the NO/cGMP pathway as a definitive treatment for AS in humans. Well-designed in vivo AS animal pharmacological models are needed to explore the other pathways involved, supporting the concept of pharmacological modulation.

Abstract

Nitric oxide (NO) induces vasodilation in various types of shock. The effect of pharmacological modulation of the NO pathway in anaphylactic shock (AS) remains poorly understood. Our objective was to assess, through a systematic review, whether inhibition of NO pathways (INOP) was beneficial for the prevention and/or treatment of AS. A predesigned protocol for this systematic review was published in PROSPERO (CRD42019132273). A systematic literature search was conducted till March 2022 in the electronic databases PubMed, EMBASE, Scopus, Cochrane and Web of Science. Heterogeneity of the studies did not allow meta-analysis. Nine hundred ninety unique studies were identified. Of 135 studies screened in full text, 17 were included in the review. Among six inhibitors of NO pathways identified, four blocked NO synthase activity and two blocked guanylate cyclase downstream activity. Pre-treatment was used in nine studies and post-treatment in three studies. Five studies included both pre-treatment and post-treatment models. Overall, seven pre-treatment studies from fourteen showed improvement of survival and/or arterial blood pressure. Four post-treatment studies from eight showed positive outcomes. Overall, there was no strong evidence to conclude that isolated blockade of the NO/cGMP pathway is sufficient to prevent or restore anaphylactic hypotension. Further studies are needed to analyze the effect of drug combinations in the treatment of AS.

Effects of NO/cGMP inhibitors in a rat model of anaphylactoid shock

Anaphylactic shock can be defined as an acute syndrome, and it is the most severe clinical manifestation of allergic diseases. Anaphylactoid reactions are similar to anaphylactic events but differ in the pathophysiological mechanism. Nitric oxide (NO) inhibitors during anaphylaxis suggest that NO might decrease the signs and symptoms of anaphylaxis but exacerbate associated vasodilation. Therefore, blocking the effects of NO on vascular smooth muscle by inhibiting the guanylate cyclase (GC) would be a reasonable strategy. This study aimed to investigate the effects of NO/cGMP pathway inhibitors methylene blue (MB), N^ω-nitro-L-arginine methyl ester hydrochloride (L-NAME), and indigo carmine (IC) in shock induced by compound 48/80 (C48/80) in rats. The effect was assessed by invasive blood pressure measurement. Shock was initiated by C48/80 intravenous bolus injection 5 min before (prophylactic) or after (treatment) the administration of the inhibitors MB (3 mg/kg), L-NAME (1 mg/kg), and IC (3 mg/kg). Of the groups that received drugs as prophylaxis for shock, only the IC group did not present the final systolic blood pressure (SBP) better than the C48/80 group. Regarding shock treatment with the drugs tested, all groups had the final SBP similar to the C48/80group. Altogether, our results suggested that inhibition of GC and NO synthase in NO production pathway was not sufficient to revert hypotension or significantly improve survival.

Sphingosine-1-phosphate receptor 2 protects against anaphylactic shock through suppression of endothelial nitric oxide synthase in mice

BACKGROUND

Sphingosine-1-phosphate receptor 2 (S1P(2)) is expressed in vascular endothelial cells (ECs). However, the role of S1P(2) in vascular barrier integrity and anaphylaxis is not well understood. Endothelial nitric oxide synthase (eNOS) generates nitric oxide to mediate vascular leakage, compromising survival in patients with anaphylaxis. We recently observed that endothelial S1P(2) inhibits Akt, an activating kinase of eNOS.

OBJECTIVE

We tested the hypothesis that endothelial S1P(2) might suppress eNOS, exerting a protective effect against endothelial barrier disruption and anaphylaxis.

METHODS

Mice deficient in S1P(2) and eNOS underwent antigen challenge or platelet-activating factor (PAF) injection. Analyses were performed to examine vascular permeability and the underlying mechanisms.

RESULTS

S1pr2 deletion augmented vascular leakage and lethality after either antigen challenge or PAF injection. PAF injection induced activation of Akt and eNOS in the aortas and lungs of S1pr2-null mice, which were augmented compared with values seen in wild-type mice. Consistently, PAF-induced increase in cyclic guanosine monophosphate levels in the aorta was enhanced in S1pr-null mice. Genetic Nos3 deletion or pharmacologic eNOS blockade protected S1pr2-null mice from aggravation of barrier disruption after antigen challenge and PAF injection. ECs isolated from S1pr2-null mice exhibited greater stimulation of Akt and eNOS, with enhanced nitric oxide production in response to sphingosine-1-phosphate or PAF, compared with that seen in wild-type ECs. Moreover, S1pr2-deficient ECs showed more severe disassembly of adherens junctions with augmented S-nitrosylation of β-catenin in response to PAF, which was restored by pharmacologic eNOS blockade.

CONCLUSION

S1P(2) diminishes harmful robust eNOS stimulation and thereby attenuates vascular barrier disruption, suggesting potential usefulness of S1P(2) agonists as novel therapeutic agents for anaphylaxis.

Nitric oxide and β(2)-adrenoceptor activation attenuate pulmonary vasoconstriction during anaphylactic hypotension in anesthetized BALB/c mice

Systemic anaphylaxis accompanies pulmonary vasoconstriction and bronchoconstriction, which may contribute to increased right heart afterload, and finally anaphylactic hypotension. However, the pulmonary response to anaphylaxis is not known in mice. We determined the pulmonary vascular and bronchial response to systemic anaphylaxis in anesthetized BALB/c mice. We also clarified the roles of β-adrenoceptors, nitric oxide, and cyclooxygenase metabolites in these responses. Anaphylaxis was induced by an intravenous injection of the ovalbumin antigen into open-chest artificially ventilated sensitized mice. Mean arterial pressure, systolic pulmonary arterial pressure, central venous pressure, airway pressure, and aortic blood flow were continuously measured. In sensitized control mice, mean arterial pressure, and aortic blood flow substantially decreased soon after the antigen injection, while systolic pulmonary arterial pressure and airway pressure did not increase. In contrast, in mice pretreated with either the β(2)-adrenoceptor antagonist ICI 118,551 (0.2 mg/kg; n = 6), or L-NAME (50 mg/kg; n = 6), but not with the β(1)-adrenoceptor antagonist atenolol (2 mg/kg; n = 6) or indomethacin (5 mg/kg; n = 6), systolic pulmonary arterial pressure increased by 7 mmHg at 1.5 min after antigen. In L-NAME pretreated mice, pulmonary hypertension was sustained over 30 min of the experimental period. Airway pressure did not significantly change after antigen in any mice studied. In conclusion, pulmonary response to systemic anaphylaxis does not increase the right heart afterload and, therefore, may not contribute to the initial decrease in venous return and anaphylactic hypotension in anesthetized mice. β(2)-adrenoceptor activation and nitric oxide, but not β(1)-adrenoceptor activation or cyclooxygenase metabolites, attenuate the antigen-induced pulmonary vasoconstriction.

Methylene blue administration in the compound 48/80-induced anaphylactic shock: hemodynamic study in pigs

PURPOSE

To verify if the methylene blue (MB) administration prevents and/or reverses the compound 48/80 (C48/80)-induced anaphylactic shock in pigs.

METHODS

Female Dalland pigs were anesthetized and had the hemodynamic parameters recorded during the necessary time to administer some drugs and observe their effect. The animals were randomly assigned to one of the five groups: 1) control; 2) MB: the animals received a bolus injection of MB (2 mg/kg) followed by continuous infusion of MB (2.66 mg/Kg/h delivered by syringe infusion pump); 3) C48/80: the animals received a bolus injection of C48/80 (4 mg/kg); 4) C48/80+MB: the animals received a bolus injection of C48/80 (4 mg/kg) and 10 minutes after the C48/80 administration the animals received a bolus injection of MB (2 mg/kg) followed by continuous infusion of MB (2.66 mg/Kg/h delivered by syringe infusion pump); 5) MB+C48/80: the animals received a bolus injection of MB (2 mg/kg) and 3 minutes later they received a bolus injection of C48/80 (4 mg/kg).

RESULTS

The intravenous infusion of MB alone caused no changes in the mean arterial pressure (MAP) showing that the administered MB dose was safe in this experimental model. The C48/80 was effective in producing experimental anaphylactic shock since it was observed a decrease in both MAP and cardiac output (CO) after its administration. The MB did not prevent or reverse the C48/80-induced anaphylactic shock in this model. In fact, the MAP of the animals with anaphylactic shock treated with MB decreased even more than the MAP of the animals from the C48/80 group. On the other hand, the C48/80-induced epidermal alterations disappeared after the MB infusion.

CONCLUSION

Despite our data, the clinical manifestations improvement brings some optimism and does not allow excluding the MB as a possible therapeutic option in the anaphylactic shock.

Understanding the mechanisms of anaphylaxis

PURPOSE OF REVIEW

The present review considers recent reports that identify the roles of key intermediate signaling components and mediators during and after mast cell activation and degranulation leading to anaphylaxis.

RECENT FINDINGS

Mechanisms of anaphylaxis are becoming better understood as the interaction of several regulatory systems in the mast cell activation and degranulation signaling cascade. Multiple tyrosine kinases, activated after immunoglobulin E binding to the high-affinity receptors for immunoglobulin E (FcepsilonRI), exert both positive and negative regulation on the signaling cascade, which may vary with genetic background or mutations in signaling proteins. Calcium influx, the essential, proximal intracellular event leading to mast cell degranulation, is controlled also by both negative and positive regulation through calcium channels. Sphingosine-1-phosphate is emerging as a newly realized mediator of anaphylaxis, acting as a signaling component within the mast cell and as a circulating mediator.

SUMMARY

Anaphylaxis is a systemic reaction involving multiple organ systems, but it is believed that it may be influenced by cellular events in mast cells and basophils resulting in the release of mediators. Therefore, understanding the mechanisms of mast cell activation and degranulation is critical to understanding the mechanisms of anaphylaxis. Recent reports have identified important regulatory components of the signaling cascade and, consequently, potential targets for therapeutic intervention.

Involvement of splanchnic vascular bed in anaphylactic hypotension in anesthetized BALB/c mice

Using in vivo and isolated perfused liver preparations of BALB/c mice, we determined the roles of the liver and splanchnic vascular bed in anaphylactic hypotension. Intravenous injection of ovalbumin antigen into intact-sensitized mice decreased systemic arterial pressure (Psa) from 92 ± 2 to 39 ± 3 (SE) mmHg but only slightly increased portal venous pressure (Ppv) from 6.4 ± 0.1 cmH2O to the peak of 9.9 ± 0.5 cmH2O at 3.5 min after antigen. Elimination of the splanchnic vascular beds by ligation of the celiac and mesenteric arteries, combined with total hepatectomy, attenuated anaphylactic hypotension. Ligation of these arteries alone, but not partial hepatectomy (70%), similarly attenuated anaphylactic hypotension. In contrast, isolated sensitized mouse liver perfused portally at constant flow did not show anaphylactic venoconstriction but, rather, substantial constriction in response to the anaphylaxis-associated platelet-activating factor, indicating that venoconstriction in mice in vivo may be induced by mediators released from extrahepatic tissues. These results suggest that splanchnic vascular beds are involved in BALB/c mouse anaphylactic hypotension. They presumably act as sources of chemical mediators to cause the anaphylaxis-induced portal hypertension, which induced splanchnic congestion, resulting in a decrease in circulating blood volume and, thus, systemic arterial hypotension. Mouse hepatic anaphylactic venoconstriction may be induced by factors outside the liver, but not by anaphylactic reaction within the liver.

Effects of l-NAME on thromboxane A2-induced venoconstriction in isolated perfused livers from rat, guinea pig and mouse

Effects of L-NAME on U-46619 (a thromboxane A(2), analogue) -induced hepatic segmental venoconstriction were examined in mouse, rat and guinea pig isolated perfused livers. All livers were perfused portally and recirculatingly at a constant flow with diluted blood. U-46619 was administrated into the reservoir in a cumulative manner to gain the concentrations of 0.001-3 microM at 10 min after L-NAME or D-NAME (100 microM). The portal venous pressure, hepatic venous pressure and perfusate flow were monitored. In addition, the sinusoidal pressure was measured by the double occlusion pressure, and was used to determine the pre- (Rpre) and post-sinusoidal (Rpost) resistances. U-46619 concentration-dependently caused predominant presinusoidal constriction in all three species. The rat livers were the strongest while the mouse livers were the weakest in responsiveness and sensitivity to U-46619. L-NAME mainly augmented the U-46619-induced increases in Rpre, but not in Rpost, in rat and guinea pig. This augmentation was stronger in rat. However, L-NAME did not augment the response to U-46619 in mouse. In conclusion, in rat and guinea pig, NO may be released selectively from the presinusoids in response to U-46619, and then attenuate the U-46619-induced presinusoidal constriction. In mouse, U-46619-induced venoconstriction is weak and not modulated by NO.