Primary structure of guinea pig plasma prekallikrein

Using guinea pigs in studies relevant to asthma and COPD

The guinea pig has been the most commonly used small animal species in preclinical studies related to asthma and COPD. The primary advantages of the guinea pig are the similar potencies and efficacies of agonists and antagonists in human and guinea pig airways and the many similarities in physiological processes, especially airway autonomic control and the response to allergen. The primary disadvantages to using guinea pigs are the lack of transgenic methods, limited numbers of guinea pig strains for comparative studies and a prominent axon reflex that is unlikely to be present in human airways. These attributes and various models developed in guinea pigs are discussed.

Generation of active fragments from human zymogens in the brady kinin-generating cascade by extracellular proteases from Vibrio vulnificus and V. parahaemolyticus

Vibrio vulnificus is an opportunistic human pathogen causing septicemia, and the infection is characterized by formation of the edematous skin lesions on limbs. This pathogenic species secretes a thermolysin-like metalloprotease as a virulence determinant. The metalloprotease was confirmed to activate human factor XII-plasma kallikrein-kinin cascade that results in liberation of bradykinin, a chemical mediator enhancing the vascular permeability, from high-molecular weight kininogen. Namely, the metalloprotease showed to generate active fragments by cleavage of Arg-Ile, Arg-Val or Gly-Leu peptide bond in human zymogens (plasma prekallikrein and factor XII). In spite of induction of the sufficient vascular permeability-enhancing and edema-forming reaction in the guinea pig model, a serine protease from V. parahaemolyticus, a human pathogen causing primarily watery diarrhea, showed far less ability to activate and to cleave the human zymogens. These results in part may explain why only V. vulnificus often causes serious edematous skin damages in humans.

Primary structures of guinea pig high- and low-molecular-weight kininogens

Guinea pig high-molecular-weight and low-molecular-weight (HMW and LMW) kininogen cDNA were amplified from liver mRNA by RT-PCR. Their nucleotide sequences were analyzed and deduced to amino acid sequences. The HMW kininogen, composed of 607 amino acid residues with a 18-residue signal sequence, possessed the cysteine protease inhibitor domains I and II, the bradykinin domain, the histidine-rich region, and the prekallikrein-binding region. The amino acid sequence preceding the bradykinin domain was found not to be -Leu-Met-Lys- but -Leu-Thr-Arg-. Therefore, kallidin (Lys-bradykinin) and Met-kallidin are not liberated from the guinea pig kininogens. We purified the HMW kininogen protein from plasma and prepared the kinin-free form using guinea pig plasma kallikrein. Although the amino-terminal of the HMW kininogen was modified, the 25 amino-terminal residues of the light chain of the kinin-free kininogen corresponded to the deduced sequence just after the bradykinin moiety of the HMW kininogen. With regard to the LMW kininogen, the nucleotide sequence down to T(1200) as well as the amino acid sequence till Thr(382) was identical to that of the HMW kininogen. We also examined the localization of the guinea pig kininogen gene on the prometaphase lymphocyte chromosomes by fluorescence in situ hybridization method. Two pair signals were observed on a pair of homologous chromosomes, each of which is composed of two chromatids. Based on these findings, we concluded that HMW and LMW kininogens are produced from the single kininogen gene in guinea pig as in the cases of the other mammalian species reported so far.