Reliable measurement of plasma kinin peptides: Importance of preanalytical variables

Hereditary Angioedema with Normal C1 Inhibitor: an Updated International Consensus Paper on Diagnosis, Pathophysiology, and Treatment

Hereditary angioedema (HAE) has been recognized for almost 150 years. The newest form of HAE, where C1 inhibitor levels are normal (HAE-nC1INH), was first described in 2000. Over the last two decades, new types of apparent non-mast cell-mediated angioedema with normal quantity and activity of C1INH have been described, in some cases with proven genetic pathogenic variants that co-segregate with angioedema expression within families. Like HAE due to C1INH deficiency, HAE-nC1INH patients are at risk of serious morbidity and mortality. Therefore, proactive management and treatment of HAE-nC1INH patients after an expert physician diagnosis is critically important. The underlying pathophysiology responsible for the angioedema has also been clarified in some of the HAE-nC1INH types. While several clinical guidelines and practice parameters including HAE-nC1INH have been published, we have made substantial progress in our understanding encompassing diagnostic criteria, pathophysiology, and treatment outcomes. HAE International (HAEi) and the US HAE Association (HAEA) convened a symposium of global HAE-nC1INH experts to synthesize our current knowledge in the area. Given the paucity of high-level evidence in HAE-nC1INH, all recommendations are based on expert opinion. This review and expert opinion on the best practice approach to diagnosing and treating HAE-nC1INH will support physicians to better manage patients with HAE-nC1INH.

Bradykinin produced during Plasmodium falciparum erythrocytic cycle drives monocyte adhesion to human brain microvascular endothelial cells

Cerebral malaria (CM) pathogenesis is described as a multistep mechanism. In this context, monocytes have been implicated in CM pathogenesis by increasing the sequestration of infected red blood cells to the brain microvasculature. In disease, endothelial activation is followed by reduced monocyte rolling and increased adhesion. Nowadays, an important challenge is to identify potential pro-inflammatory stimuli that can modulate monocytes behavior. Our group have demonstrated that bradykinin (BK), a pro-inflammatory peptide involved in CM, is generated during the erythrocytic cycle of P. falciparum and is detected in culture supernatant (conditioned medium). Herein we investigated the role of BK in the adhesion of monocytes to endothelial cells of blood brain barrier (BBB). To address this issue human monocytic cell line (THP-1) and human brain microvascular endothelial cells (hBMECs) were used. It was observed that 20% conditioned medium from P. falciparum infected erythrocytes (Pf-iRBC sup) increased the adhesion of THP-1 cells to hBMECs. This effect was mediated by BK through the activation of B2 and B1 receptors and involves the increase in ICAM-1 expression in THP-1 cells. Additionally, it was observed that angiotensin-converting enzyme (ACE) inhibitor, captopril, enhanced the effect of both BK and Pf-iRBC sup on THP-1 adhesion. Together these data show that BK, generated during the erythrocytic cycle of P. falciparum, could play an important role in adhesion of monocytes in endothelial cells lining the BBB.

Editorial: Kinin 2022 Meeting, Annecy, France

The Kinin 2022 meeting took place at the Imperial Palace, Annecy, France, from 5-8 June 2022 [...].

Mass spectrometric study of variation in kinin peptide profiles in nasal fluids and plasma of adult healthy individuals

BACKGROUND

The kallikrein-kinin system is assumed to have a multifunctional role in health and disease, but its in vivo role in humans currently remains unclear owing to the divergence of plasma kinin level data published ranging from the low picomolar to high nanomolar range, even in healthy volunteers. Moreover, existing data are often restricted on reporting levels of single kinins, thus neglecting the distinct effects of active kinins on bradykinin (BK) receptors considering diverse metabolic pathways. A well-characterized and comprehensively evaluated healthy cohort is imperative for a better understanding of the biological variability of kinin profiles to enable reliable differentiation concerning disease-specific kinin profiles.

METHODS

To study biological levels and variability of kinin profiles comprehensively, 28 healthy adult volunteers were enrolled. Nasal lavage fluid and plasma were sampled in customized protease inhibitor prespiked tubes using standardized protocols, proven to limit inter-day and interindividual variability significantly. Nine kinins were quantitatively assessed using validated LC-MS/MS platforms: kallidin (KD), Hyp4-KD, KD1-9, BK, Hyp3-BK, BK1-8, BK1-7, BK1-5, and BK2-9. Kinin concentrations in nasal epithelial lining fluid were estimated by correlation using urea.

RESULTS

Circulating plasma kinin levels were confirmed in the very low picomolar range with levels below 4.2 pM for BK and even lower levels for the other kinins. Endogenous kinin levels in nasal epithelial lining fluids were substantially higher, including median levels of 80.0 pM for KD and 139.1 pM for BK. Hydroxylated BK levels were higher than mean BK concentrations (Hyp3-BK/BK = 1.6), but hydroxylated KD levels were substantially lower than KD (Hyp4-KD/KD = 0.37). No gender-specific differences on endogenous kinin levels were found.

CONCLUSIONS

This well-characterized healthy cohort enables investigation of the potential of kinins as biomarkers and would provide a valid control group to study alterations of kinin profiles in diseases, such as angioedema, sepsis, stroke, Alzheimer's disease, and COVID-19.

Picomolar Sensitivity Analysis of Multiple Bradykinin-Related Peptides in the Blood Plasma of Patients With Hereditary Angioedema in Remission: A Pilot Study

Background

Hereditary angioedema (HAE) is a rare autosomal dominant disease; the most well understood forms concern the haplodeficiency of C1 esterase inhibitor (C1INH) and a gain of function mutation of factor XII (FXII). The acute forms of these conditions are mediated by an excessive bradykinin (BK) formation by plasma kallikrein.

Methods

A validated LC-MS/MS platform of picomolar sensitivity developed for the analysis of eleven bradykinin-related peptides was applied to the plasma of HAE-C1INH and HAE-FXII sampled during remission.

Results

In HAE-C1INH plasma, the concentrations of the relatively stable BK1−5 fragment (mean ± S.E.M.: 12.0 ± 4.2 pmol/L), of BK2−9 (0.7 ± 0.2 pmol/L) and of the sums of BK and its tested fragments (18.0 ± 6.4 pmol/L) are significantly greater than those recorded in the plasma of healthy volunteers (1.9 ± 0.6, 0.03 ± 0.03 and 4.3 ± 0.8 pmol/L, respectively), consistent with the previous evidence of permanent plasma kallikrein activity in this disease. Kinin levels in the plasma of HAE-FXII patients did not differ from controls, suggesting that triggering factors for contact system activation are not active during remission.

Conclusion

BK1−5, BK2−9 and the sum of BK and its fragments determined by the sensitive LC-MS/MS technique are proposed as potential biomarkers of HAE-C1INH in remission while this was not applicable to HAE-FXII patients.