Bradykinin
Also known as: BK, Bradykinin (1-9), H-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg-OH, Kallidin-9, Kinin, RPPGFSPFR
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Summary
Bradykinin is a nine‑amino‑acid vasoactive peptide that modulates blood‑vessel tone, renal function and inflammatory responses. In humans it is generated from high‑molecular‑weight kininogen and acts primarily through G‑protein‑coupled B1 and B2 receptors, producing vasodilation, increased vascular permeability and pain. Excessive bradykinin activity underlies several forms of angioedema, especially hereditary angioedema (HAE) and ACE‑inhibitor‑induced swelling.
Mechanism of Action
Bradykinin binds to cell‑surface B2 receptors (constitutively expressed) and inducible B1 receptors, both seven‑transmembrane GPCRs. Activation triggers phospholipase C, intracellular calcium rise and nitric‑oxide release, leading to vasodilation and heightened endothelial permeability. The peptide is rapidly degraded by enzymes such as angiotensin‑converting enzyme (ACE) and neprilysin; inhibition of these peptidases raises bradykinin levels, amplifying its physiological and pathological effects.
What the Research Shows
Clinical reviews identify bradykinin as the common mediator of angioedema in hereditary C1‑inhibitor deficiency, acquired C1‑inhibitor loss, ACE‑inhibitor therapy and other non‑allergic forms. Targeted therapies—C1‑INH concentrates, the B2‑receptor antagonist icatibant, and the kallikrein inhibitor ecallantide—have improved attack management. Pharmacological studies describe B1 and B2 receptor subtypes, their tissue distribution and distinct roles in acute versus chronic inflammation. Recent work on neprilysin inhibitors highlights a therapeutic dilemma: while raising bradykinin may benefit cardiovascular and renal outcomes, it also increases angioedema risk, as seen with omapatrilat and, to a lesser extent, LCZ696. A systematic review estimates HAE prevalence at roughly 1.2 per 100,000 worldwide, underscoring the rarity but clinical importance of bradykinin‑driven disease.
Reported Benefits
Evidence from randomized and open‑label studies supports the use of icatibant (B2‑antagonist) and ecallantide (kallikrein inhibitor) to shorten the duration of bradykinin‑mediated angioedema attacks. C1‑INH replacement therapy remains the standard for hereditary and acquired forms. Physiologically, bradykinin contributes to vasodilation, renal perfusion and protection against ischemia‑reperfusion injury, suggesting potential benefits of modestly elevated levels in cardiovascular disease, although clinical confirmation is limited.
Limitations of the Evidence
Therapeutic data are confined mainly to acute angioedema; there are few controlled trials evaluating bradykinin‑targeted interventions for chronic inflammatory or cardiovascular conditions. The exact contribution of B1 versus B2 receptors in human disease remains incompletely defined, and the long‑term safety of sustained bradykinin elevation is uncertain. Prevalence estimates for HAE vary by region, reflecting heterogeneity in diagnostic criteria and reporting.
Safety Considerations
Elevated bradykinin can precipitate life‑threatening laryngeal edema, hypotension and flushing. ACE inhibitors and neprilysin inhibitors increase bradykinin levels and are associated with angioedema, with incidence ranging from 0.5 % to over 2 % in some trials. While B2‑antagonists like icatibant are generally well tolerated, clinicians must monitor for injection‑site reactions and rare hypersensitivity. Patients with a history of angioedema should avoid drugs that raise bradykinin without prophylactic measures.
How It Is Administered
In research settings bradykinin has been administered by inhalation, intra‑arterial, intravenous or topical routes, typically as sterile peptide solutions. Formulations are short‑acting, requiring careful dosing and rapid monitoring due to the peptide’s potent vasoactive effects.
Routes of Administration
Goals & Uses
- Wound healing / tissue repairRegenerativeLow
- Vasodilation / blood pressure reductionCardiovascularHigh
- Research tool for pain sensitizationNeuroscience / ResearchHigh
- Cardioprotection (ischemic preconditioning)CardiovascularModerate
- Provocative testing (bronchial / vascular)DiagnosticModerate
- pain sensitizationNeurologicalModerate
- induce vasodilationCardiovascularHigh
Contraindications
- Severe asthma / BronchospasmRespiratoryHigh
- History of bradykinin-mediated angioedemaAllergic / ImmunologicHigh
- PregnancyPopulationHighPotential fetal risk or insufficient safety data
- Hypotension / Hemodynamic instabilityCardiovascularHigh
- Severe hypotensionCardiovascularHigh
Adverse Effects
- Tachycardia (reflex)CardiovascularUncommon
- HypotensionCardiovascularCommonLow blood pressure
- FlushingVascularCommonWarmth and redness of the skin
- BronchoconstrictionRespiratoryUncommon
- pain/flushingSensoryCommon
- Pain / Burning sensationNeurologicalCommon
- AngioedemaImmunologicRare
Drug Interactions
- NSAIDs (e.g., indomethacin, ibuprofen)Moderate
- Angiotensin Receptor Blockers (ARBs)Low
- NSAIDsLowMay increase renal risk in susceptible patients
- ACE inhibitorsModerate
- Nitrates / Nitric oxide donorsModerate
- ACE Inhibitors (e.g., enalapril, lisinopril)High
Population Constraints
- pediatric subjectsAgeRelative
- Elderly patientsAgeRelative
- Patients on ACE inhibitor therapyPharmacologicalAbsolute
- Pregnant womenReproductiveRelative
- Patients with hereditary angioedema (HAE)Genetic / ImmunologicAbsolute
- Asthmatic patientsRespiratoryRelative
Regulatory Status
- European UnionUnapprovedNo marketing authorization; available for investigational use.
- United StatesUnapprovedUsed only in research settings; not an FDA‑approved therapeutic.
- United KingdomUnapprovedNot approved by MHRA as a therapeutic. Research use only.
Bradykinin itself is not an approved therapeutic agent in any major jurisdiction. It is used as a research tool and in diagnostic/provocative testing contexts. Its antagonists (e.g., icatibant) and the bradykinin pathway are major therapeutic targets for hereditary angioedema.
Evidence & Sources
- Journal ArticleModerateObtułowicz K2016-01-01T00:00:00.000000Z
- Journal ArticleModerateKaplan AP2014-01-01T00:00:00.000000Z
- Journal ArticleModerateHall JM1997-01-01T00:00:00.000000Z
- Journal ArticleModerateCampbell DJ2018-01-01T00:00:00.000000Z
- Journal ArticleHighFisch SA, et al.2025-01-01T00:00:00.000000Z
Frequently Asked Questions
What conditions are driven by excess bradykinin?
The main clinical manifestation is angioedema, occurring in hereditary C1‑inhibitor deficiency, acquired C1‑inhibitor loss, ACE‑inhibitor therapy and some idiopathic forms. Bradykinin also contributes to inflammation and vascular tone regulation.
How are bradykinin‑mediated attacks treated?
Acute attacks are managed with C1‑INH concentrate, the B2‑receptor antagonist icatibant, or the kallikrein inhibitor ecallantide. These agents reduce swelling faster than conventional antihistamines or corticosteroids, which are ineffective against bradykinin.
Can drugs that increase bradykinin be used safely?
Agents such as ACE inhibitors and neprilysin inhibitors raise bradykinin and can improve cardiovascular outcomes, but they carry a risk of angioedema. The risk varies by patient population and drug combination; monitoring for swelling is essential.
What is the prevalence of hereditary angioedema?
A systematic review estimated a global prevalence of about 1.2 cases per 100,000 people, with lower rates reported in Asia and Africa and higher rates in Europe and North America.
Are there different bradykinin receptors?
Yes. The B2 receptor is constitutively expressed and mediates acute vasodilation and edema, while the inducible B1 receptor is up‑regulated during inflammation and appears to play a role in chronic pain and hyperalgesia.
What is Bradykinin used for?
Bradykinin is educationally associated with: Wound healing / tissue repair, Vasodilation / blood pressure reduction, Research tool for pain sensitization, Cardioprotection (ischemic preconditioning), Provocative testing (bronchial / vascular), pain sensitization, induce vasodilation. Educational only — not medical advice.
How is Bradykinin administered?
Recorded routes of administration: Inhalation, Intra Arterial, Intracerebroventricular, Intravenous, Topical.
What are the potential side effects of Bradykinin?
Reported adverse effects include: Tachycardia (reflex), Hypotension, Flushing, Bronchoconstriction, pain/flushing, Pain / Burning sensation, Angioedema. This list is not exhaustive — consult a qualified clinician.
Who should avoid Bradykinin?
Recorded contraindications: Severe asthma / Bronchospasm, History of bradykinin-mediated angioedema, Pregnancy, Hypotension / Hemodynamic instability, Severe hypotension. Consult a qualified clinician before use.