Protective Effects of Safranal Against Spike Protein-Induced Mitochondrial Dysfunction and Inflammation in Peripheral...

Saffron (Crocus sativus L.) contains bioactive molecules with antioxidant, anti-inflammatory, and neuroprotective properties. Growing evidence indicates that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) promotes neuroinflammation and mitochondrial dysfunction contributing to neuro-coronavirus disease.

The aim of this study is to evaluate the antioxidant, anti-inflammatory, and neuroprotective effects of 3 saffron derivatives, picrocrocin, 4-hydroxysafranal, and safranal, in peripheral immune cells and microglia, and to test the hypothesis that these compounds, especially safranal, counteract Spike protein 1(S1)-induced inflammation and mitochondrial dysfunction.

An immortalized murine microglial cell line (BV2) and human peripheral blood mononuclear cells (PBMCs) from healthy donors were treated with saffron derivatives at nontoxic concentrations (0.05-0.5 mM). Cytotoxicity (3-(4,5-dimethylthiazol-2-yl)-5-(3‑carboxymethoxyphenyl)-2-(4‑sulfophenyl)-2H‑tetrazolium (MTS) assay), antioxidant capacity [2,2-diphenyl-1-picrylhydrazyl (DPPH)], intracellular reactive oxygen species (ROS; 2,7-dichlorodihydrofluorescein diacetate), cytokine expression (enzyme-linked immunosorbent assay and quantitative polymerase chain reaction), and mitochondrial membrane potential (5,5',6,6'‑tetrachloro‑1,1',3,3'‑tetraethylbenzimidazolylcarbocyanine iodide (JC-1) assay) were assessed. Lipopolysaccharide (LPS) served as an inflammatory control, whereas S1 was used to model SARS-CoV-2-mediated neuroinflammation and mitochondrial damage.

All saffron derivatives showed antioxidant activity, with safranal demonstrating the strongest DPPH radical scavenging effect and the most pronounced reduction of intracellular ROS. In LPS-stimulated BV2 cells, safranal significantly decreased inducible nitric oxide synthase expression. In PBMCs, saffron compounds attenuated LPS-induced interleukin-1 beta (IL-1β) release, with safranal showing the greatest decrease. S1 increased IL-1β and tumor necrosis factor-alpha expression in BV2 microglia. Co-treatment with safranal reduced these cytokines by ∼38% and 44%, respectively. S1 induced a loss of mitochondrial membrane potential, which was effectively restored by safranal, as confirmed by JC-1 fluorescence analysis.

These findings identify safranal as a promising neuroprotective candidate for preventing or mitigating SARS-CoV-2-associated neurological damage and other disorders involving microglial activation and mitochondrial impairment.