The part immediately following what you quoted about melatonin is of interest for PMR which involves chronic inflammation:

"In the early phase of inflammation, which is necessary for healing to occur in response to an acute insult, melatonin activates proinflammatory mediators including phospholipase A2 and arachidonate 5-lipoxygenase. This activation is a transient phenomenon and extinguishes within 2–3 hours. In the late inflammation phase, which refers to chronic inflammation responsible for many disease processes, melatonin exerts anti-inflammatory effects by downregulating the aforementioned inflammatory mediators and pro-inflammatory cytokines and also by reducing oxidative stress (Radogna et al., 2010)."