Identification of cDNA for rat homologues of human major basic protein and eosinophil cationic protein

Mammalian antimicrobial proteins and peptides: overview on the RNase A superfamily members involved in innate host defence

The review starts with a general outlook of the main mechanisms of action of antimicrobial proteins and peptides, with the final aim of understanding the biological function of antimicrobial RNases, and identifying the key events that account for their selective properties. Although most antibacterial proteins and peptides do display a wide-range spectrum of action, with a cytotoxic activity against bacteria, fungi, eukaryotic parasites and viruses, we have only focused on their bactericidal activity. We start with a detailed description of the main distinctive structural features of the bacteria target and on the polypeptides, which act as selective host defence weapons.Following, we include an overview of all the current available information on the mammalian RNases which display an antimicrobial activity. There is a wealth of information on the structural, catalytic mechanism and evolutionary relationships of the RNase A superfamily. The bovine pancreatic RNase A (RNase A), the reference member of the mammalian RNase family, has been the main research object of several Nobel laureates in the 60s, 70s and 80s. A potential antimicrobial function was only recently suggested for several members of this family. In fact, the recent evolutionary studies indicate that this protein family may have started off with a host defence function. Antimicrobial RNases constitute an interesting example of proteins involved in the mammalian innate immune defence system. Besides, there is wealth of available information on the mechanism of action of short antimicrobial peptides, but little is known on larger polypeptides, that is, on proteins. Therefore, the identification of the mechanisms of action of antimicrobial RNases would contribute to the understanding of the proteins involved in the innate immunity.

Characterization of biological activities of feline eosinophil granule proteins

OBJECTIVE

To characterize eosinophil granule-derived proteins in cats.

SAMPLE POPULATION

Eosinophils collected via peritoneal lavage from 2 cats.

PROCEDURE

The cats were infested orally with Toxocara canis eggs and subsequently challenge-exposed with T. canis antigen injected IP to induce peritoneal eosinophilia; eosinophils were collected via peritoneal lavage. Eosinophil granule proteins were acid-extracted, separated by gel-filtration chromatography, and examined for their peroxidase, ribonuclease, and bactericidal activities; the N-terminal sequence of some of these proteins was determined and compared with homologue proteins from other species.

RESULTS

3 protein peaks were separated in the chromatogram. The first peak had both peroxidase and bactericidal activities. The second peak had ribonuclease and bactericidal activities, and the N-terminal sequence of the major protein was homologous with that of proteins of the ribonuclease A superfamily, including eosinophil ribonucleases from humans and other animal species. The third protein peak had bactericidal activity, and the N-terminal sequence of the major protein was homologous with that of human and murine major basic proteins.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that feline eosinophil granules contain major basic protein and eosinophil-associated ribonuclease and the granule proteins have peroxidase, ribonuclease, and bactericidal activities. In cats, characterization of eosinophil granule proteins may be useful in elucidation of the mechanism of tissue damage in eosinophil-associated diseases and development of new treatment options for those diseases. In addition, the identification of conserved structure and function of eosinophil granule proteins in cats is relevant from an evolutionary viewpoint.

Preparation of recombinant rat eosinophil-associated ribonuclease-1 and -2 and analysis of their biological activities

Rat eosinophils contain eosinophil-associated ribonucleases (Ears) in their granules. Ears are thought to be synthesized as pre-forms and stored in the granules as mature forms. However, the N-terminal amino acid of mature Ear-1 and Ear-2 is still controversial. Therefore, we prepared two recombinant mature forms of Ear-1 and Ear-2 in which the N-terminal amino acids are Ser24 (S) [Ear-1 (S) and Ear-2 (S)] and Gln26 (Q) [Ear-1 (Q) and Ear-2 (Q)], and analyzed their biological activities by comparing them with those of pre-form Ear-1 and pre-form Ear-2. The four mature Ears showed RNase A activity as well as bovine pancreatic RNase A activity, but pre-Ear-1 and pre-Ear-2 showed no RNase A activity. Mature Ear-1 (Q) and mature Ear-2 (Q) showed more potent RNase A activity than mature Ear-1 (S) and mature Ear-2 (S), respectively. The RNase A activities of mature Ear-1 (Q) and mature Ear-2 (Q) were reduced by treatment at 96 degrees C for 20 min or with RNase inhibitor. The growth of Escherichia coli was inhibited by both pre-Ears and mature Ears in a concentration-dependent manner, and was almost completely suppressed at 1.0 microM. The bactericidal activities of mature Ear-1 (Q) and mature Ear-2 (Q) were not inhibited by RNase inhibitor, but was increased by treatment at 96 degrees C for 20 min.

An ex vivo perfusion model to evaluate hyperacute rejection in a discordant pig-to-human combination

Inadequate supplies of human organs for transplantation have evoked an escalating interest in human xenotransplantation. Hyperacute rejection precludes use of discordant organs. We have developed an ex vivo perfusion model in order to evaluate hyperacute rejection in a pig-to-human combination. Pig kidneys (n = 6) perfused with human blood deteriorated rapidly and rejection was seen after 70 (60–87) min (median, 95% confidence interval). Kidneys perfused with pig blood survived 300 (216–360) min, corresponding to the upper time limit of the model. Increases in prostaglandin E₂ and 6-keto-prostaglandin F_1α indicated endothelial activation. Sequential blood samples revealed a strong progressive inflammatory response with reduced leukocyte and platelet counts, granulocyte activation indicated by increased myeloperoxidase, and complement activation, shown by an increase in C3 activation products and the terminal SC5b-9 complement complex. A significant role for classical pathway activation was indicated by formation of C1rs-C1 inhibitor complexes and activation of C4, whereas factor B was not significantly activated. Biopsies at rejection demonstrated hyperacute rejection with inflammatory changes involving the vessels as well as the nephrons. Where the inflammatory markers could be studied in pig blood, activation was less than in human blood. The present discordant xenotransplant model is a valuable adjunct for evaluation of changes occurring in the human blood perfusate as well as in the pig kidney during hyperacute rejection.