Hymenoptera venom anaphylaxis: may decreased levels of angiotensin peptides play a role?

IgE-Mediated Systemic Anaphylaxis And Its Association With Gene Polymorphisms Of ACE, Angiotensinogen And Chymase

BACKGROUND

The renin-angiotensin system (RAS) protects the circulation against sudden falls in systemic blood pressure via generation of angiotensin II (AII). Previously, we demonstrated that patients with anaphylaxis involving airway angioedema and cardiovascular collapse (AACVS) had significantly increased "I" gene polymorphisms of the angiotensin-converting-enzymes (ACE). This is associated with lower serum ACE and AII levels and was not seen in anaphylaxis without collapse nor atopics and healthy controls.

OBJECTIVES

To examine the angiotensinogen (AGT-M235T) and chymase gene (CMA-1 A1903G) polymorphisms in these original subjects.

METHOD

122 patients with IgE-mediated anaphylaxis, 119 healthy controls and 52 atopics had polymorphisms of the AGT gene and chymase gene examined by polymerase chain reactions and gel electrophoresis. Their previous ACE genotypes were included for the analysis.

RESULTS

AGT-MM genes (associated with low AGT levels) were significantly increased in anaphylaxis (Terr's classification). When combined with ACE, anaphylaxis showed increased MM/II gene pairing (p<0.0013) consistent with lower RAS activity. For chymase, there was increased pairing of MM/AG (p<0.005) and AG/II and AG/ID (p<0.0073) for anaphylaxis consistent with lower RAS activity. A tri-allelic ensemble of the 6 commonest gene combinations for the healthy controls and anaphylaxis confirmed this difference (p=0.0001); for anaphylaxis, genes were predominately MM/AG/II or ID, while healthy controls were DD/MT/AG or GG patterns.

CONCLUSION

Our gene polymorphisms show lower RAS activity for anaphylaxis especially AACVS. Animal models of anaphylaxis are focused on endothelial nitric oxide (eNO) which is shown to be the mediator of fatal shock and prevented by eNO-blockade. The interaction of AII and eNO controls the microcirculation in man. High serum AII levels reduce eNO activity, so higher RAS-activity could protect against shock. Our data shows low RAS activity in anaphylaxis especially AACVS, suggesting the influence of these genes on shock are via AII levels and its effects on eNO.

IgE-Mediated Anaphylaxis to Foods, Venom, and Drugs: Influence of Serum Angiotensin Converting Enzyme Levels and Genotype

Circulating angiotensin-II protects the circulation against sudden falls in blood pressure and is generated by the enzymatic action of angiotensin converting enzyme (ACE) on angiotensin-I. The ACE genes have 2 allelic forms, “I” and “D.” The “D” genotype has both highest angiotensin-II generation and serum ACE levels compared to “I”. 120 patients with IgE-anaphylaxis, 119 healthy controls, and 49 atopics had serum ACE levels, ACE genotype, and renin levels determined. Plasma renin levels were identical for all groups. Serum ACE levels and genotypes were similar for healthy controls (HC) and atopics, but lower in anaphylaxis (P = 0.012), with ACE genotypes also showing increased “I” genes (P = 0.009). This effect was more pronounced in subjects manifesting airway angioedema and cardiovascular collapse (AACVS) than mild cutaneous and respiratory (CRA) symptoms. AACVS was significantly associated with the presence of “I” genes. For “ID” genotype OR is 5.6, 95% CI 1.8 to 17.4, and for “II” genotype OR is 44, 95% CI 5 to 1891 within the anaphylaxis group = 0.001. The results show a difference in the genotype frequency between control and anaphylaxis, suggesting a role for the renin angiotensin system in anaphylaxis manifesting with airway angioedema and cardiovascular collapse.

Association between the renin angiotensin system and anaphylaxis

Patients with hymenoptera venom anaphylaxis before immunotherapy (n = 50) showed significantly lower renin, angiotensinogen, angiotensin I and angiotensin II as compared to healthy non-allergic controls (n = 25) (p < 0.05). A significant inverse correlation between the severity of clinical symptoms and the plasma levels of renin, angiotensinogen, angiotensin I and angiotensin II was found: the lower the levels the more severe the clinical symptoms. Hymenoptera venom allergic patients with repeated anaphylactic reactions during hyposensitizatin did not tolerate the sting of a living insect (n = 6). Sting provocation with a living insect induced clinical symptoms of anaphylaxis in all of the 6 patients. Renin, angiotensinogen, angiotensin I and II remained significantly lower in these patients as compared to healthy non-allergic controls. Likewise, no stimulation of the renin angiotensin system occurred during the anaphylactic reaction. The values of angiotensin II were similar or lower than the values before the anaphylactic reaction. In contrast, patients with successful immunotherapy (n = 27) who tolerated the sting of a living insect, renin, angiotensin I and II were significantly higher than in patients without immunotherapy. After immunotherapy, the values for renin, ANG I and ANG II were similar to the values found in healthy non-allergic controls. Patients with a history of hymenoptera venom anaphylaxis (n = 22) showed significantly lower ANG II concentrations in their leukocytes as compared to healthy non-allergic controls (n = 24). Successful immunotherapy induced a significant 9-fold increase in ANG II as compared to patients without immunotherapy. These findings suggest a possible role of the renin angiotensin system in hymenoptera venom anaphylaxis.

Plasma concentrations of arginine vasopressin, oxytocin and angiotensin in patients with hymenoptera venom anaphylaxis

The plasma concentrations of arginine vasopressin, oxytocin, angiotensin I and II were studied in patients with hymenoptera venom anaphylaxis (n = 50) and healthy volunteers (n = 25). There was no difference in arginine vasopressin: 5.52 +/- 0.45 fmol/ml vs. 3.99 +/- 0.41 fmol/ml or oxytocin: 28.10 +/- 1.13 fmol/ml vs. 26.24 +/- 1.80 fmol/ml between patients and controls. No correlation between the severity of clinical symptoms and the plasma levels of arginine vasopressin and oxytocin was found in patients. However, patients with a history of hymenoptera venom anaphylaxis showed significantly reduced angiotensin I and angiotensin II plasma levels as compared to controls (ANG I: 9.51 +/- 0.61 fmol/ml vs. 22.91 +/- 1.73 fmol/ml; ANG II: 2.84 +/- 0.16 fmol/ml vs. 6.95 +/- 0.33 fmol/ml). A significant inverse correlation between the severity of clinical symptoms and the plasma levels of angiotensin I and angiotensin II was observed; the lower the concentrations the more severe the clinical symptoms. Oxytocin immunoreactivity eluted from the HPLC column as a single peak with the same retention time as synthetic oxytocin. The vasopressin immunoreactive material could be characterized on HPLC as arginine-vasopressin and two other peptides of unknown nature which crossreacted with the vasopressin antibody. These findings suggest a possible role of angiotensin I and angiotensin II in hymenoptera venom anaphylaxis while arginine vasopressin and oxytocin are most likely not involved.

The renin angiotensin system and hymenoptera venom anaphylaxis

Components of the renin angiotensin system, namely renin, angiotensinogen, angiotensin I and II and aldosterone were measured in plasma of patients with hymenoptera venom anaphylaxis (n = 50) and healthy non-allergic controls (n = 25). Patients with a history of anaphylactic reactions to hymenoptera venom who did not undergo immunotherapy showed significantly reduced renin, angiotensinogen, angiotensin I and angiotensin II in plasma as compared with controls (P < 0.05). There was no difference in the aldosterone concentration between patients and controls. Angiotensin I, angiotensin II, renin and angiotensinogen levels were the same in male and female patients. There was also no difference in the angiotensin I, II, renin or angiotensinogen levels between young and older patients. A significant inverse correlation between the severity of clinical symptoms and the plasma levels of renin (r = -0.382, P < 0.001), angiotensinogen (r = -0.567, P < 0.0001), angiotensin I (r = -0.656, P < 0.0001) and angiotensin II (r = 0.0762, P < 0.0001) was found: the lower the levels the more severe the clinical symptoms. No correlation was found for aldosterone. Hymenoptera venom allergic patients with repeated anaphylactic reactions during hyposensitization did not tolerate the sting of a living insect (n = 6). In these patients, renin, angiotensinogen, angiotensin I and II remained significantly lower than in healthy non-allergic controls. Patients with successful immunotherapy (n = 27) who tolerated the sting of a living insect had renin, angiotensin I and II significantly higher than patients without immunotherapy. These findings suggest a possible role of the renin angiotensin system in hymenoptera venom anaphylaxis.

Loratadine. A review of recent findings in pharmacology, pharmacokinetics, efficacy, and safety, with a look at its use in combination with pseudoephedrine

Antihistamines are considered first-line therapy for the relief of symptoms from allergic rhinitis and chronic urticaria. The newer, second-generation, nonsedating antihistamines reduce the central nervous system and anticholinergic side effects commonly found with previous drugs. The availability of H1-receptor antagonists that produce therapeutic effects without causing unwanted CNS effects fulfills an important practical need, since these drugs are clearly preferable in patients who drive or operate heavy machinery, or who are involved in activities requiring full alertness. Physicians and patients alike are pleased with the efficacy and safety the second-generation antihistamines bring to the treatment of allergy symptoms. Loratadine is an especially effective second-generation H1-receptor antagonist and is comparable to many of the other second-generation antihistamines. Loratadine may be particularly advantageous because of its low dose and the convenience of once-daily dosing. A more subtle advantage, loratadine's antiallergic properties, may warrant its use for specific treatment situations as future research clarifies the nature of the inflammatory response and the mechanisms of action antiallergic antagonists have in this regard.