Figure 5.

Antihyperalgesic effect of HMWH is CD44-dependent. A, Rats were treated daily with a spinal intrathecal injection of ODN sense or antisense for CD44 mRNA (120 μg) for 3 consecutive days. On the fourth day, TNFα (100 ng, left) or IL-6 (10 ng, right) was injected intradermally on the dorsum of the hindpaw. Thirty minutes later, vehicle (white bars) or HMWH (1 μg, black bars) was injected at the same site. Evaluation of the mechanical nociceptive threshold 30 min later showed a significant reversal of the hyperalgesia induced by TNFα and IL-6 in the groups that had been treated with antisense, compared with those treated with sense (TNFα, sense groups: t₍₁₀₎ = 7.306, ****p < 0.0001; antisense groups: t₍₁₀₎ = 1.007, p = 0.1688, nonsignificant; IL-6, sense groups: t₍₁₀₎ = 9.077, ****p < 0.0001; antisense groups: t₍₁₀₎ = 0.8891, p = 0.1974, nonsignificant, when the vehicle and HMWH groups are compared, unpaired Student's t test). B, Rats received four intraperitoneal injections of the chemotherapeutic drug paclitaxel (1 mg/kg, every other day). Intrathecal injections of ODN sense or antisense were performed, once a day, from days 5–7 of paclitaxel treatment. At 24 h after the last injections of paclitaxel and ODNs, vehicle (white bars) or HMWH (1 μg, black bars) was injected intradermally on the dorsum of the hindpaw. Mechanical nociceptive threshold was evaluated before treatment with paclitaxel and 30 min after the injection of vehicle or HMWH. Significant attenuation of paclitaxel-induced hyperalgesia was observed only in the ODN sense-treated group (t₍₁₀₎ = 4.781, ***p = 0.0004, compared with the antisense-treated group, unpaired Student's t test). Together, these results indicate that HMWH acts at CD44 to produce antihyperalgesia. n = 6 paws, all groups.