L-Arginine-Modified Chitosan Curcumin Nanocrystals Target M1 Macrophages via CAT-2/Clathrin-Mediated Endocytosis for Mitochondrial Protection and ALI/ARDS Therapy

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Abstract
Background: Acute Lung Injury/Acute Respiratory Distress Syndrome (ALI/ARDS) is a fatal inflammatory disorder driven by M1 macrophages and the associated inflammatory cascade. Targeted drug delivery to these cells is a promising therapeutic strategy. Methods: L-arginine was conjugated to chitosan of different molecular weights. The resulting curcumin nanocrystals (Arg-CS-Cur) were characterized for conjugation efficiency, zeta potential, stability, and drug release profile. Cellular uptake mechanisms and mitochondrial targeting were investigated in lipopolysaccharide (LPS)-induced M1 macrophages using specific endocytic inhibitors and confocal microscopy. Results: Low-molecular-weight chitosan (MW 50 kDa) showed the highest L-Arg conjugation efficiency (22.31%). The optimized Arg-CS-Cur nanocrystals exhibited high zeta potential (±47.5 mV), excellent stability, and a superior drug release. They were internalized by M1 macrophages more efficiently than unmodified CS-Cur or free curcumin (p < 0.05). Uptake occurred via clathrin-mediated endocytosis (p < 0.001) and was mediated by CAT-2, which was highly expressed in M1 macrophages (p < 0.001). Arg-CS-Cur specifically targeted the mitochondria, reducing ROS and NLRP3 expression, thus inhibiting the NLRP3 inflammasome pathway (p < 0.001). Conclusions: This L-arginine-modified chitosan-based nanodelivery system synergistically exploits CAT-2 and clathrin pathways to deliver curcumin to M1 macrophage mitochondria, inhibiting the NLRP3 inflammasome. This dual-targeted strategy offers a promising approach for treating ALI/ARDS.

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