675.3.2.3 Simulation of CFA by SNP and Suppression of CIAA by
l-NMMA
To make sure that NO is an initiator of synovitis, we used SNP for intra-articu-
lar injection to simulate CFA-induced CIAA. Consequently, we noticed that SNP
(0.5–1.0 mg/ml) can mimic CFA (0.5–1.0 mg/ml) to cause erythema and edema in
both injected and noninjected paws. From the results of histochemical analysis, we
confirmed that SNP can simulate CFA to induce the synoviocyte propagation and
inflammatory infiltration. Among 84 hypoxia signaling genes, SNP downregulates
NOS2 for 2.98-folds, HIF- 1 α for 2.28-folds, and HYOU- 1 for 4.01-folds, whereas
CFA upregulates NOS2 for 2.04-folds, HIF- 1 α for 1.24-folds, and HYOU- 1 for
1.83-folds. These data suggested that SNP-released NO could repress the expres-
sion of hypoxia-sensitive genes, whereas the overexpression of those genes occurs
upon induction by CFA-activated proinflammatory cytokines.
The intra-articular injection of mice by CFA causes the erythematous and
edematous paws, which are similar with those seen in mice injected by CII-CFA.
When CFA was coinjected with l-NMMA, however, no significant erythema and
edema occur in mouse paws. Accordingly, CFA injection allows a higher SpO 2 ,
whereas CFA + l-NMMA exhibits a lower SpO 2 (Table 5.2).
Fig. 5.2 Induction of accelerated angiogenesis (a), enhanced HIF-1α expression (b), and
enhanced VEGF expression (c) in the synovial tissue of CIAA mice (200×). CIAA collagen-
induced chronic arthritis; HIF- 1 α hypoxia-inducible factor α; VEGF vascular endothelial growth
factor
Table 5.2 Effects of l-NMMA on CFA-induced synovial hypoxia in mice
C FA complete Freund’s adjuvant; l-NMMA NG-monomethyl-l-arginine monoacetate; SpO 2 satu-
ration percentages of O 2. Intra-articular injection was performed using 100 μl of drug/drug com-
binations. The singular asterisk (*) represents different from the control (p < 0.05)
Treatment SpO 2 (%)
CFA (0.5 mg/ml) into a left hind leg 77.33 ± 1.20*
CFA (1 mg/ml) into a right hind leg 72.67 ± 1.55*
l-NMMA (0.5 mg/ml) + CFA (0.5 mg/ml) into a right hind leg 86.67 ± 2.87
l-NMMA (0.5 mg/ml) + CFA (1 mg/ml) into a left hind leg 96.75 ± 3.10
CFA (0.5 mg/ml) injection into a right hind leg 72.00 ± 1.96*
CFA (0.5 mg/ml) + l-NMMA (0.5 mg/ml) into a right hind leg 90.75 ± 2.02
Control 98.33 ± 0.58