(A) Left: Intra-paw injection of HC-HA/PTX3 (10 μg or 20 μg, 20 μl), but not vehicle (saline), increased paw withdrawal latency (PWL) to heat stimulation in naive WT mice. N = 8–11/group. Right: Intra-paw injection of HC-HA/PTX3 (10 μg or 20 μg, 20 μl) dose-dependently attenuated the heat hypersensitivity during Days 2–4 after plantar-incision. N = 9–16/group. (B) Right: Intra-paw injection of HC-HA/PTX3 (20 μg, 20 μl) showed superior anti-hyperalgesic effect compared to high-molecular-weight hyaluronan (HMW-HA) (20 μg, 20 μl) alone and the mixture of HMW-HA (20 μg) and HC1 (720 ng) during Days 2–4 after plantar-incision. Left: Analyzing the area under the curve (AUC) to assess the anti-hyperalgesic effect of each group. N = 5–9/group. (C) HC-HA/PTX3 inhibited the calcium responses evoked by capsaicin (a TRPV1 agonist, 0.3 μM) in WT DRG neurons. HC-HA/PTX3 alone did not evoke [Ca2+]i elevation. Pretreatment (20 min) of HC-HA/PTX3 (15 μg/ml, bath application) reduced capsaicin-evoked [Ca2+]i rising. (D) The quantification of [Ca2+]i rising evoked by capsaicin in DRG neurons pretreated with the vehicle, HC-HA/PTX3 (15 μg/ml), or HMW-HA (15 μg/ml). N = 109–170 neurons/group. (E) Left: Traces show that the β-alanine (a MrgprD agonist, 1 mM) evoked an increase in [Ca2+]i, which was also inhibited by HC-HA/PTX3. Right: The quantification of evoke [Ca2+]i rising by β-alanine. N = 10–25 neurons/group. (F) Left: Traces show that cinnamaldehyde (a TRPA1 agonist, 1 mM) evoked an increase in [Ca2+]i, which was inhibited by HC-HA/PTX3. Right: The quantification of evoke [Ca2+]i rising by cinnamaldehyde. N = 15–35 neurons/group. (G) An example trace of membrane potential (Vm) which changed from resting level (−60 mV) toward a more hyperpolarized state after HC-HA/PTX3 (10 μg/ml) in a small DRG neuron (insert, scale bar: 25 μm). Vm returned to pre-drug level after washout. DRG neurons were categorized according to cell body diameter as <20 μm (small), 20–30 μm (medium), and >30 μm (large). (H) Example traces of action potentials (APs) evoked by injection of current in small DRG neurons 5 min after bath application of vehicle or HC-HA/PTX3 (5, 25 μg/ml). (I) HC-HA/PTX3 concentration-dependently altered the intrinsic membrane properties of small DRG neurons. Quantification of the resting membrane potential (RMP) before and at 5 min after bath application of vehicle or HC-HA/PTX3 (5, 10, and 25 μg/ml). N = 4–7/group. (J) Quantification of rheobase in small DRG neurons at 5 min after vehicle or HC-HA/PTX3. The rheobase after the drug was normalized to pre-drug value. N = 5–7/group. Data are mean ± SEM. (A, B: right) Two-way mixed model analysis of variance (ANOVA) followed by Bonferroni post hoc test. *p < 0.05, **p < 0.01, ***p < 0.001 versus vehicle; #p < 0.05, ##p < 0.01, ###p < 0.001 versus pre-drug. (B: left, C) One-way ANOVA followed by Bonferroni post hoc test. ***p < 0.001 versus vehicle; ##p < 0.01 versus other groups. (E, F) Paired t-test. ***p < 0.001 versus vehicle. (I, J) Two-way mixed model ANOVA followed by Bonferroni post hoc test. *p < 0.05, **p < 0.01 versus pre-drug.
Figure 3—source data 1. Numerical source data files for Figure 3.