Corticostatin 1

The human neutrophil-derived cationic peptide HP-4 exhibits corticostatic activity on adrenal cells and is an L-type calcium channel agonist at nanomolar concentrations. Complementary DNA clones encoding the HP-4 precursor have been isolated from a human bone marrow cDNA library by screening with oligonucleotide probes. The nucleotide sequence shares about 72% identity with the cDNA encoding defensin HP-1, but differs from it, and from other genes of this family characterized to date, by an extra 83-base segment. This extra segment is not adjacent to an intron and is apparently the result of a recent duplication within the coding region corresponding to most of the mature HP-4 peptide. The predicted amino acid sequence shows the HP-4 precursor structure to be typical of this family of molecules. By analysis of DNA from a pannel of hamster/human hybrid cell lines, the HP-4 gene was found to be on chromosome 8, as is the gene for human peptide HP-1. Comparison with the few sequences of other corticostatin/defensin genes available does not indicate distinct lineages of corticostatic and noncorticostatic peptides, since HP-1 and HP-4 cDNA sequences share more identity with each other than either shares with cDNAs encoding rabbit MCP-1 or MCP-2, or guinea pig GNCP-1.

We report the isolation and characterization of RK-1, a novel peptide found in the kidney. RK-1 is related to the corticostatin/defensins and has the sequence MPC-SCKKYCDPWEVIDGSCGLFNSKYCCREK but differs from the very cationic corticostatins/defensins in having only one arginine and a calculated charge at pH 7 of +1. Like some myeloid corticostatin/defensins RK-1 inhibits the growth of Escherichia coli. Since corticostatin/defensins effect ion flux in responsive epithelia we used volume changes in villus enterocytes as a model system to study the effects of RK-1 on ion channels in epithelial cells. At concentrations > or = 10(-9) M RK-1 decreased enterocyte volume in a dose-dependent manner through a pathway that requires extracellular calcium and is inhibited by niguldipine, a dihydropyridine-sensitive "L"-type Ca(2+)-channel blocker. In other assay systems for corticostatin-defensins, such as the inhibition of adrenocorticotropin-stimulated steroidogenesis, or cell lysis, RK-1 was inactive or only weakly active. These results demonstrate the existence of a novel system of biologically active peptides in the kidney represented by RK-1 which is antimicrobial and can activate epithelial ion channels in vitro.

Using an antiserum against synthetic rabbit corticostatin-1 (CS-1), we established a specific RIA for CS-1 and examined its distribution in various tissues, including the hypothalamic-pituitary-adrenal axis. Among the tissues examined, the highest levels of CS-1-like immunoreactivity (-LI) were found in the lung and spleen. CS-1-LI was also detected at relatively high levels in the pituitary, adrenal medulla, and small intestine, while it was barely detectable in the hypothalamus. Immunocytochemical studies revealed the widespread distribution of CS-1 in these tissues. Plasma CS-1 levels averaged 7.8 ng/ml and increased to 185.4 ng/ml in the presence of infection. CS-1-LI in the adrenal gland, small intestine, and hypothalamus also increased in rabbits with active inflammation. These data suggest that CS-1 may modify the hypothalamic-pituitary-adrenal axis in an endocrine or paracrine manner in response to infection.