Elsevier

Neuroscience

Volume 116, Issue 4, 28 February 2003, Pages 1043-1052
Neuroscience

Research paper
Effect of endotoxin treatment on the expression on cyclooxygenase-2 and prostaglandin synthases in spinal cord, dorsal root ganglia, and skin of rats

https://doi.org/10.1016/S0306-4522(02)00783-2Get rights and content

Abstract

Peripheral inflammation causes upregulation of cyclooxygenase in the spinal cord and subsequent increase in prostaglandin biosynthesis. However, prostaglandin synthases, which are downstream of cyclooxygenase control the type of prostaglandin that is formed predominantly. Since there is little known about the regulation of prostaglandin synthases, the present study was conducted in order to determine the effect of endotoxin treatment on the expression of messenger RNA encoding interleukin 1β, cyclooxygenase-2, and prostaglandin synthases mediating the formation of prostaglandin E2 (membrane bound prostaglandin E synthase) and prostaglandin D2 (lipocalin prostaglandin D synthase) in spinal cord, dorsal root ganglia and skin of rats.

Endotoxin (2 mg/kg i.p.) induced the expression of interleukin-1β, cyclooxygenase-2, and membrane bound prostaglandin E synthase messenger RNA in spinal cord, dorsal root ganglia, and skin as determined by reverse transcription polymerase chain reaction. In contrast, basal expression of lipocalin prostaglandin D synthase messenger RNA in spinal cord and dorsal root ganglia was not significantly altered by endotoxin. Dexamethasone (1 mg/kg s.c. at −18 h and −1 h) attenuated the effect endotoxin on the expression of interleukin-1β, cyclooxygenase-2, and membrane bound prostaglandin E synthase messenger RNA in all tissues investigated, but did not significantly influence expression of lipocalin prostaglandin D synthase mRNA in spinal cord and dorsal root ganglia. In situ hybridisation histochemistry showed endotoxin-induced expression of cyclooxygenase-2 and membrane bound prostaglandin E synthase messenger RNA throughout gray and white matter of spinal cord sections. In dorsal root ganglia, expression of membrane bound prostaglandin E synthase seemed primarily located to non-neuronal cells, while cyclooxygenase-2 messenger RNA was not detectable.

The results show that the immune response elicited by endotoxin induced cyclooxygenase-2 and membrane bound prostaglandin E synthase, but not lipocalin prostaglandin D synthase messenger RNA in spinal cord and dorsal root ganglia of rats. The distribution of cyclooxygenase-2 and membrane bound prostaglandin E synthase messenger RNA expressing cells suggests major involvement of non-neuronal cells in spinal prostaglandin biosynthesis. Determination of the regulation of enzymes downstream of cyclooxygenase at the messenger RNA level may represent a valuable tool to investigate effects of analgesic/anti-inflammatory drugs on the regulation of spinal prostaglandin biosynthesis.

Section snippets

Animals

The study was approved by the ethics committee of the Federal Ministry of Education, Science and Culture of the Republic of Austria and carried out in line with the European Communities Council Directive in such a way that animal suffering and the number of animals needed was minimised. Male Sprague–Dawley rats (200–300 g body wt.; Himberg, Austria) received an i.p. injection of 2 mg/kg endotoxin (LPS; lipopolysaccharide Escherichia coli Serotype 055:B5; Sigma, Vienna, Austria) or vehicle. Four

Results

Treatment of rats with endotoxin induced the expression of IL-1β mRNA in skin, DRG, and spinal cord, whilst in the control group the mRNA signal remained below the detection limit of the reverse transcription polymerase chain reaction (RT-PCR) protocol (Fig. 1, Fig. 2). Endotoxin treatment also induced the expression of COX-2 mRNA (Fig. 1, Fig. 2) and significantly enhanced expression of mPGES mRNA in all tissues investigated (Fig. 1, Fig. 3). In contrast, endotoxin did not significantly

Discussion

It is known that systemic administration of endotoxin, a lipopolysaccharide component of the outer membrane of Gram-negative bacteria, triggers an increase in the circulating levels of various cytokines (Andersson et al., 1992). In the present study, we have observed prompt stimulation of the expression of IL-1β mRNA in peripheral and CNS tissue following endotoxin administration to rats, suggesting successful induction of an immune response. Several studies have focussed on the mechanisms by

Acknowledgements

The authors wish to thank I. Lanz and M. Ofner for expert technical assistance. The study was supported by the Fonds zur Förderung der Wissenschaftlichen Forschung (P-13512-Med). R. Ulcar received financial support from the Natural Sciences Faculty of the Karl Franzens Universität Graz.

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