A putative role for leucocyte products in the regulation of acute inflammation

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Crouch, S.P.M., 1991. A putative role for leucocyte products in the regulation of acute inflammation. PhD, Nottingham Trent University.

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Abstract

The acute inflammatory response involves the recruitment of leucocytes from the peripheral circulation to sites of injury/infection. Mononuclear cells (MNC) activated at the inflammatory foci are capable of affecting PMN function through the secretion of certain cytokines. We have shown that, in vitro, TNF is produced maximally after by MNC 5-6 hours in culture with lug ml-1 bacterial lipopolysaccharide (LPS). This TNF primed polymorphonuclear leucocytes (PMN) for a dramatic, and irreversible, increase in respiratory burst activity when stimulated with zymosan-activated serum (ZAS) (323.29% ± 57.94%, n=15 ± SEM).

Direct stimulatory activity of MNC-conditioned medium (MNCM) was not due to TNF, IL-1beta or GM-CSF. Sephadex G-75 and G-50 filtration demonstrated at least one low molecular weight (<12.3kD) factor in MNCM which directly stimulated PMN superoxide anion production. NAP-1/IL-8 was thought involved in this bioactivity as antiserum to this peptide reduced PMN superoxide anion production by 46.64% ± 11.46% (n=4 ± SEM, p<0.025). However, only one of three recombinant human NAP- 1/IL-8 preparations induced a dose dependent increase in PMN respiratory burst activity. It was possible that NAP-1/IL-8 secreted vitro from LPS stimulated MNC had greater activity than the recombinant forms, or that other low molecular weight factors were involved.

Recombinant human TNF induced increased CD11b and CD18 expression concomitant with lactoferrin (Lf) release, suggesting that this cytokine could potentially increase PMN adhesiveness. The role of Lf released at the same time may act as a negative regulator of inflammation. Adding 10-10 M 50%-Fe-saturated Lf to MNC cultures stimulated with LPS, resulted in significant reduction of TNF (p<0.025) and IL-1beta (p<0.05) production. Lf also inhibited the proliferation of 3-way mixed lymphocyte cultures (MLC) at 24, 48 and 72 hours, together with inhibition of TNF and IL-1beta production.

Finally, the effects of pentoxifylline (PTOX) were investigated with respect to PMN function. vivo data obtained after administration of 1 x 400mg slow release PTOX revealed that depressed superoxide anion production in response to ZAS and formyl-methionylleucylphenylalanine (FMLP) correlated with levels of metabolite V (MET V) (p<0.04). In vitro data confirmed MET V. to be the most effective at reducing PMN respiratory burst, Lf release and CD11b/CD18 expression. These findings suggested that PTOX may reduce PMN associated tissue damage, in conditions such as varicose ulceration, via its metabolites rather than the parent drug.

Item Type:

Thesis

Creators:

Crouch, S.P.M.

Date:

1991

ISBN:

9781369324198

Identifiers: