ASIC3 and Osteoarthritis

ASIC3 modulates pain and disease progression

Neuromics' foundation is built on providing reagents for pain researchers. I have posted the twists and turns via key publications and related data. Here's yet another success story with one of our Pain and Inflammation Research Antibodies.

Acid sensing ion channels (ASICs) are sodium-selective ion channels activated by low extracellular pH, and belong to the degenerin/epithelial Na+ channel superfamily. ASIC3  is the most sensitive to such a pH change [2,3], abundantly expressed in dorsal root ganglia (DRG) [4], and strongly correlated with pain. Here researchers show the role of ASIC3 in osteoarthritis: Masashi Izumi, Masahiko Ikeuchi, Qinghui Ji, Toshikazu Tani. Local ASIC3 modulates pain and disease progression in a rat model of osteoarthritis. Journal of Biomedical Science 2012, 19:77 doi:10.1186/1423-0127-19-77.
Highlights: OA was induced via intra-articular mono-iodoacetate (MIA) injection, and pain related behaviors were evaluated including weight bearing measured with an incapacitance tester and paw withdrawal threshold in a von Frey hair test. OA rats showed not only weight-bearing pain but also mechanical hyperalgesia outside the knee joint (secondary hyperalgesia). ASIC3 expression in knee joint afferents was significantly upregulated approximately twofold at Day 14. Continuous intra-articular injections of APETx2 inhibited weight distribution asymmetry and secondary hyperalgesia by attenuating ASIC3 upregulation in knee joint afferents. Histology of ipsilateral knee joint showed APETx2 worked chondroprotectively if administered in the early, but not late phase.

Images: Fast Blue labeling and immunohistochemistry staining for ASIC3 : (a-b) Naïve- model, (c-d) OA-model, (e-f) APETx2 administration to OA-model in early phase. Photos in each row are the same DRG. In (b),(d),(f), large arrows indicate Fast Blue labeled, ASIC3 immunoreactive (ASIC3-ir) DRG cells, while ASIC3-ir cells that were not labeled by Fast Blue are indicated by small arrowheads. More than 100 FB-labeled neurons were analyzed from 4 rats in each group. The percentage of ASIC3-ir knee joint afferents was 18 ± 3% (mean ± SD) in naïve models, 46 ± 4% in OA-models (p = 0.003), and 20 ± 5% in the early-phase APETx2 group (p = 0.006), respectively. Scale bar: 50 μm

Protocol: The [DRG] sections were blocked in 3% normal goat serum for 1 h, then incubated in primary antibody of ASIC3 (Neuromics; Edina, MN, GP 14015, 1:500) overnight in a humid chamber. The next day, the sections were incubated in the secondary antibody (Vector; Burlingame, CA, FI-7000, 1:500, FITC tagged) for 2 h. All antisera used were diluted in PBS containing 1% normal goat serum and 0.05% Triton X-100. Before, between, and after each incubation step, the sections were washed 3 times for 5 min in PBS. Finally, all sections were mounted with Vectashield (Vector, Burlingame, CA).
1. Waldmann R, Champigny G, Bassilana F, Heurteaux C, Lazdunski M: A proton-gated cation channel involved in acid-sensing. Nature 1997, 386:173–177. 2. Lingueglia E: Acid-sensing ion channels in sensory perception. J Biol Chem 2007, 282:17325–17329. note: see http://neuromics.net/weblog/post/tag/dr-eric-lingueglia/ for research using our siRNA transfectio reagent for ASIC3 gene expression analysis. 
3. Wemmie JA, Price MP, Welsh MJ: Acid-sensing ion channels: advances, questions and therapeutic opportunities. Trends Neurosci 2006, 29:578–586.
4. Voilley N, de Weille J, Mamet J, Lazdunski M: Nonsteroid anti-inflammatory drugs inhibit both the activity and the inflammation-induced expression of acid-sensing ion channels in nociceptors. J Neurosci 2001, 21:8026–8033.