Neutrophil adhesion to glomerular mesangial cells: regulation by lipoxygenase-derived eicosanoids

Photodynamic therapy upregulates expression of Mac-1 and generation of leukotriene B4 by human polymorphonuclear leukocytes

This study investigated the expression of Mac-1 (CD11b/CD18) and generation of leukotriene B(4) (LTB(4)) by polymorphonuclear leukocytes (PMNs) in response to Mono-L-aspartyl chlorine 6 (NPe6) mediated photodynamic therapy (PDT). PDT was carried out using a laser diode at a light dose of 10 J/cm(2) and wavelength of 664 nm. Expression of Mac-1 was significantly increased about 3-fold by PDT compared with that of Npe6 exposure. The increase in the expression of Mac-1 was not inhibited by 5-lipoxygenase inhibitor (AA861). On the other hand, generation of LTB(4) by PMNs was increased by incubation with NPe6 alone and further promoted by PDT and that was significantly inhibited by AA861. These results suggest that PDT can induce PMNs to express extensively Mac-1 and generate a certain amount of LTB(4) that may play an important cytocidal role in the treatment of oral cancer.

Lipoxins: pro-resolution lipid mediators in intestinal inflammation

Many inflammatory processes are self-limiting, suggesting the existence of endogenous anti-inflammatory mechanisms. Among the lipid mediators generated during cell-cell interactions are the lipoxins (LX, including LXA(4) and B(4)), a distinct class of lipoxygenase-derived eicosanoids. Aspirin acetylation of cyclooxygenase 2 also promotes the generation of a series of 15-epimers of LXA(4), known as aspirin-triggered lipoxins (ATL), that may account for some of the bioactivity profile of aspirin and possibly of nonsteroidal anti-inflammatory drugs. Native LX are rapidly inactivated in vivo, and stable analogs of LXA(4), LXB(4), and ATL have been synthesized that possess enhanced bioavailability and potency as anti-inflammatory eicosanoids. Here, we review current in vitro, ex vivo, and in vivo evidence supporting cytoprotective and proresolution roles for LX in intestinal inflammation. LXA(4), LXA(4) analogs, and ATL analogs inhibit neutrophil chemotaxis, adhesion to epithelium, and epithelial cell chemokine release. In addition, LX blunt TNF-alpha-stimulated inflammatory responses, cyclooxygenase product generation, and epithelial cell apoptosis and are cytoprotective for cytokine-activated colonic mucosa ex vivo. LX, ATL, and synthetic LX analogs have already been demonstrated to possess impressive antiinflammatory and proresolution efficacy in a range of experimental models of inflammation in vivo. Further elucidation of the role of LX in intestinal epithelial cell biology and immune function may yield novel therapeutic approaches in inflammatory bowel disease and possibly gastrointestinal cancer.

The leukotriene B4 receptor antagonist ONO-4057 inhibits nephrotoxic serum nephritis in WKY rats

To evaluate the role of leukotriene B4 (LTB4) in glomerulonephritis, this study was conducted to examine whether ONO-4057, an LTB4 receptor antagonist, moderated nephritis caused by the injection of nephrotoxic serum (NTS) into Wistar-Kyoto rats. Rats were given intraperitoneal injections of ONO-4057 or phosphate-buffered saline 24 h before the injection of NTS. These rats subsequently received equal doses of ONO-4057 or phosphate-buffered saline 3 h and 1, 2, 3, 4, 5, and 6 d later. Compared with the control groups, ONO-4057 treatment significantly reduced proteinuria and hematuria, suppressed the glomerular accumulation of monocytes/macrophages, and reduced the formation of crescentic glomeruli in a dose-dependent manner. These results suggest that LTB4 is responsible for the crescentic formations and renal dysfunction associated with NTS nephritis. The LTB4 receptor antagonist ONO-4057 may thus be beneficial in the treatment of crescentic glomerulonephritis.