Combining these results with those of our studies [27, 47], we offer a new concept that a significant increase of PGE2 level is attributable to an imbalance between the mPGES-1-dependent synthetic pathway and the 15-PGDH-dependent scavenging system in ALS model mice (Fig. 2). The gene discussed is HPGD; the disease is amyotrophic lateral sclerosis.