Manganese oxide nanozyme-loaded CO-releasing halloysite nanotubes for remodeling colonic immune, microbiota, and intestinal barrier homeostasis with concurrent pain relief in ulcerative colitis

Ulcerative colitis (UC) involves immune dysregulation, barrier dysfunction, and dysbiosis, driving chronic inflammation and pain. Current treatments show limited efficacy and high toxicity. This study develops an engineered nanozyme, CO&MnOx@Hs (CMHs), synthesized via in-situ manganese oxide (MnOx) generation on halloysite nanotubes (Hs) with controlled encapsulation of the carbon monoxide (CO)-releasing molecule CORM-401 for gas therapy. CMHs selectively accumulate at inflamed UC sites, where MnOx scavenges reactive oxygen species (ROS) while CO exerts anti-inflammatory effects. These combined actions restore immune homeostasis, repair intestinal barrier, modulate gut microbiota, and alleviate inflammation-associated pain. In murine ulcerative colitis, CMHs outperform conventional treatments, demonstrating superior therapeutic efficacy. Mechanistic studies reveal that CMHs activate Nrf2/HO-1 for antioxidant effects while modulating PI3K-Akt and HIF-1α/LDHA pathways to promote M2 macrophage polarization and suppress NF-κB/TNF signaling. CMHs also fortify the intestinal barrier by mitigating bacterial invasion and ROS-induced damage while activating focal adhesion and ECM-receptor interaction. 16S ribosomal RNA sequencing further confirms CMHs' ability to remodel gut microbiota, reinforcing their immunomodulatory potential. Importantly, CMHs relieve chronic pain by reducing inflammation, inhibiting SP secretion and TACR1 expression, and suppressing TRPV1 channel activation and Ca²⁺ influx. These findings establish CMHs as a multi-targeted and highly effective therapeutic strategy for UC.