Inhibition of Rho-associated kinase relieves C5a-induced proteinuria in murine nephrotic syndrome.

Childhood nephrotic syndrome is mainly caused by minimal change disease which is named because only subtle ultrastructural alteration could be observed at electron microscopic level in the pathological kidney. Glomerular podocytes are presumed to be the target cells whose protein sieving capability is compromised by a yet unidentified permeability perturbing factor. In a cohort of children with non-hereditary idiopathic nephrotic syndrome, we found the complement fragment C5a was elevated in their sera during active disease. Administration of recombinant C5a induced profound proteinuria and minimal change nephrotic syndrome in mice. Purified glomerular endothelial cells, instead of podocytes, were demonstrated to be responsible for the proteinuric effect elicited by C5a. Further studies depicted a signaling pathway involving Rho/Rho-associated kinase/myosin activation leading to endothelial cell contraction and cell adhesion complex breakdown. Significantly, application of Rho-associated kinase inhibitor, Y27632, prevented the protein leaking effects observed in both C5a-treated purified endothelial cells and mice. Taken together, our study identifies a previously unknown mechanism underlying nephrotic syndrome and provides a new insight toward identifying Rho-associated kinase inhibition as an alternative therapeutic option for nephrotic syndrome.

Immunological effects and therapeutic role of C5a in cancer.

The specific role of C5a in cancer, especially in melanoma, has yet to be determined. Differential effects of C5a could be cancer specific. In the host defense system, C5a functions to protect the body from harmful entities via a plethora of mechanisms. Yet, C5a may also serve to potentiate cancerous process. C5a facilitates cellular proliferation and regeneration by attracting myeloid-derived suppressor cells and supporting tumor promotion. In this article, we critically reviewed the properties, mechanisms of action and functions of C5a, with particular emphasis on cancer inhibition and promotion, and clinical application of such knowledge in better management of patients with cancer. Outstanding questions and future directions in regard to the function of C5a in melanoma and other cancers are discussed.

Effects of a new C5a receptor antagonist on C5a- and endotoxin-induced neutropenia in the rat.

A new C5a receptor antagonist, the cyclic peptide Phe-[Orn-Pro-D-cyclohexylalanine-Trp-Arg], (F-[OPdChaWR]), was tested for its ability to antagonize the neutropenic effects of both C5a and endotoxin in rats. Human recombinant C5a (2 microg kg(-1) i.v.) caused rapid neutropenia, characterized by an 83% decrease in circulating polymorphonuclear leukocytes (PMNs) at 5 min. Administration of F-[OPdChaWR] (0.3-3 mg kg(-1) i.v.), did not affect the levels of circulating PMNs but, when given 10 min prior to C5a, it inhibited the C5a-induced neutropenia by up to 70%. Administration of E. Coli lipopolysaccharide (LPS, 1 mg kg(-1) i.v.) also caused neutropenia with an 88% decrease in circulating PMNs after 30 min. When rats were pretreated with F-[OPdChaWR] (0.3 - 10 mg kg(-1) i.v.) 10 min prior to LPS, there was a dose-dependent antagonism of the neutropenia caused by LPS, with up to 69% reversal of neutropenia observed 30 min after LPS administration. These findings suggest that C5a receptor antagonists may have therapeutic potential in the many diseases known to involve either endotoxin or C5a.

Arterially perfused eye model of uveitis.

OBJECTIVE: To develop an in vitro model of uveitis based on an ex situ perfused eye to evaluate the anti-inflammatory activity of new pharmacological products. PROCEDURE: Eyes were removed from more than 60 dogs and 9 horses immediately after euthanasia and perfused with nutrient medium through the lateral long ciliary artery. Perfused eyes produced aqueous humour, and perfusion pressure was adjusted to obtain an intraocular pressure in the physiological range. When the eyes were treated with histamine, a complement C5a analogue peptide and hydrogen peroxide, typical signs of uveitis were produced. These included miosis, vascular leakage, reduced intraocular pressure, reduced flow of perfusate and, in some eyes, conjunctival oedema. RESULTS: Canine eyes showed a decrease in intraocular pressure and a decrease in perfusate flow rate when challenged with 100 mumol/L hydrogen peroxide. Flunixin meglumine (5 mumol/L), ketoprofen (5 mumol/L), indomethacin (5 mumol/L) as well as a new drug pirfenidone (10 mumol/L) prevented changes in intraocular pressure induced by hydrogen peroxide, but did not significantly moderate the mediator-induced changes in perfusate flow. CONCLUSIONS: This model is suitable for evaluating potential anti-inflammatory activity of drugs without having to induce uveitis in an experimental animal. The technique is suitable for species that range in size from cats to horses.