Abstract
Nitric oxide (NO) and prostaglandins are inflammatory mediators produced during meningitis. The purpose of the present study was to pharmacologically inhibit cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS) to 1) explore the prostaglandin contribution to blood-cerebrospinal fluid barrier permeability alterations and 2) elucidate the in vivo concentration relationship between prostaglandin E2 (PGE2) and NO during experimental meningitis. Intracisternal injection of lipopolysaccharides (LPSs, 200 μg) induced neuroinflammation. Rats were dosed with nimesulide (COX-2 inhibitor), aminoguanidine (iNOS inhibitor), or vehicle. Evans blue was used to assess blood-cerebrospinal fluid barrier permeability. Meningeal NO and cerebrospinal fluid PGE2 were assayed using conventional methods. (Results are expressed as mean ± S.E.M. of 5–9 rats/group.) Nimesulide failed to prevent blood-cerebrospinal fluid barrier disruption [cerebrospinal fluid Evans blue (micrograms per milliliter): control, 0.22 ± 0.22*; LPS, 11.58 ± 0.66; LPS + nimesulide, 10.58 ± 0.86; *p < 0.05; ANOVA]. Although nimesulide decreased PGE2 (picograms per microliter; p < 0.01) in LPS + nimesulide rats (13.9 ± 1.96) versus LPS + vehicle (73.8 ± 12.4), meningeal NO production (picomoles/30 min/106 cells; p < 0.01) increased unexpectedly in LPS + nimesulide rats (439 ± 47) versus LPS + vehicle rats (211 ± 31). In contrast, aminoguanidine inhibited meningeal NO (picomoles/30 min/106 cells;p < 0.005) in LPS + aminoguanidine (111 ± 20) versus LPS (337 ± 48) but had no effects (p > 0.05) on PGE2. The in vivo relationship between PGE2 and NO was mathematically described by a biphasic, bell-shaped curve (r2 = 0.42; n = 27 rats; p < 0.0001). Based on these results, inhibition of prostaglandin synthesis not only fails to prevent blood-cerebrospinal fluid barrier disruption during neuroinflammation and but also promotes increased meningeal NO production. The in vivo concentration relationship between PGE2 and NO is biphasic, suggesting that inhibition of COX-2 alone may promote NO toxicity through enhanced NO synthesis.
Footnotes
-
↵1 Current address: Cognigen Corporation, Buffalo, NY 14221.
-
This work was supported in part by National Institutes of Health Grant NS 31939.
-
DOI: 10.1124/jpet.102.041533
- Abbreviations:
- NO
- nitric oxide
- PGE2
- prostaglandin E2
- NOS
- nitric-oxide synthase
- iNOS
- induced nitric-oxide synthase
- COX-2
- cyclooxygenase-2
- HPLC
- high-performance liquid chromatography
- LPS
- lipopolysaccharide
- ANOVA
- analysis of variance
- IL
- interleukin
- TNF
- tumor necrosis factor
- Received July 16, 2002.
- Accepted September 30, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|