Increased kallikrein expression protects against cardiac ischemia

Area of Science:

• Cardiovascular Physiology
• Biochemistry
• Molecular Biology

Background:

• Indirect evidence suggests bradykinin plays a cardioprotective role.
• Inhibition of angiotensin-converting enzyme (ACE), or kininase II, may protect against cardiac ischemia by increasing bradykinin.
• The sufficiency of increased kinin formation for cardioprotection remains to be directly demonstrated.

Purpose of the Study:

• To investigate whether increased kinin formation is sufficient to protect the heart against ischemia and reperfusion.
• To evaluate the cardioprotective effects of enhanced bradykinin production in a transgenic rat model.

Main Methods:

• Utilized transgenic rats (TGR(hKLK1)) engineered to overexpress human tissue kallikrein in the heart.
• Isolated hearts from transgenic and wild-type rats underwent ex vivo regional ischemia and reperfusion.
• Hearts were treated with either vehicle or a bradykinin B2 receptor antagonist (HOE 140).

Main Results:

• Transgenic rats exhibited significantly reduced overflow of nucleotide breakdown products during reperfusion compared to wild-type littermates (270±57 vs. 455±54 nmol/min/g).
• This reduction suggests diminished cellular damage and improved cardiac function under ischemic stress.
• Bradykinin B2 receptor antagonism was employed to probe the mechanism of protection.

Conclusions:

• Enhanced bradykinin formation via human tissue kallikrein overexpression is sufficient to confer protection against cardiac ischemia and reperfusion injury.
• These findings support the therapeutic potential of targeting the kallikrein-kinin system for cardiovascular protection.