NOS2 and Huntington disease: HD is a bifunctional alkylating agent that reacts with cellular targets including lipids, proteins and DNA, and mechanistic aspects of HD-induced skin injuries include oxidative stress, DNA damage and cell cycle pathways, caspase and poly (ADP–ribose) polymerases (PARP), mitogen activated protein kinases (MAPKs) and Akt pathways, transcription factors activator protein-1 (AP-1) and nuclear factor- κB (NF-κB), matrix metalloprotease-9 (MMP-9), inflammatory mediators cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), cytokines, and calcium signaling [5], [6], [10]–[17].