Diterpenoids from Dictyota spp. protect BV2 microglia from OGD/REP injury by modulation of stress-related pathways

Ischemia-reperfusion (IR) injury is a complex process that comprises the restoration of oxygen flow after deprivation, which exacerbates cellular damage. Among the molecular regulators involved, cyclophilins (Cyps) have emerged as critical mediators of oxidative stress, mitochondrial dysfunction, and associated inflammation, highlighting them as promising targets. In this context, natural compounds represent an important source of bioactive molecules. The protective effects of seven previously described diterpenes (1–7), purified from two brown seaweed species of the genus Dictyota, were evaluated in a microglial IR model. Compounds were purified by preparative chromatography and identified by nuclear magnetic resonance spectroscopy and mass spectrometry. BV2 microglial cells were incubated with compounds under oxygen–glucose deprivation conditions followed by reperfusion. Cyclosporine A (CsA) was used as positive control in all assays. Cell viability, reactive oxygen species (ROS) levels and mitochondrial membrane potential (∆Ψm) were analyzed. Cyps binding interactions were studied using a surface plasmon resonance biosensor. Cyps expression and activation of HIF1α and Nrf2 pathways were evaluated by western blot, and IL-1β secretion was quantified by ELISA. Dictyota metabolites were as potent as CsA in reducing ischemia impact. When cells were reperfused, 1–7 counteracted the damage, with compounds 4 and 5 showing the strongest effects. Treatment with 1–7 also reduced ROS levels and restored ∆Ψm, indicating antioxidant and mitochondrial protective properties. Subsequently, their ability to bind Cyps was assessed, and 4, 5, and 7 displayed high affinity with equilibrium dissociation constants in the micromolar range. Therefore, the effect of metabolites on Cyps expression was analyzed. Notably, 1–7 downregulated Cyps A and D as efficiently as CsA. Interestingly, compounds modulated the activation of HIF1α and Nrf2, proteins involved in hypoxia adaptation and redox homeostasis, while CsA was ineffective. Compound 1 increased the nuclear translocation of both proteins, 3, 6, and 7 enhanced HIF1α activation, and 2 increased Nrf2 nuclear translocation. Moreover, compounds 1–7 decreased the secretion of IL-1β. This study identifies diterpenes from Dictyota spp. as promising protective agents against oxygen–glucose deprivation/reperfusion injury through the modulation of Cyps and stress-response pathways with better outcomes than CsA.