BACKGROUND Generalized pustular psoriasis (GPP) is a severe autoinflammatory dermatosis driven by excessive IL-1/IL-36-neutrophil activation, with high disease burden and limited therapeutic options. The mechanisms underlying dysregulated neutrophil recruitment remain incompletely understood, and the lack of mechanistic models that capture key inflammatory features of GPP has limited mechanistic and therapeutic investigations of GPP. Cathepsin S (CTSS), a cysteine protease involved in IL-36γ activation and neutrophil recruitment, has not been investigated in GPP. METHODS CTSS expression in GPP lesions was analyzed using public bulk RNA sequencing, single-cell RNA sequencing, and patient samples. A mouse model capable of mimicking the neutrophilic inflammatory phenotype of GPP was established by combining topical imiquimod (IMQ) treatment with intradermal CTSS injection (IMQ + CTSS). Histological, transcriptomic, flow cytometry, ELISA, and cross-species bioinformatics analysis were performed to assess consistency between patients and mice. In vitro experiments and pharmacological inhibition with LY3000328 were used to investigate the functional role of CTSS. RESULTS CTSS was markedly elevated in GPP lesions, predominantly enriched in myeloid cells, and closely associated with neutrophil chemotaxis signatures. The IMQ + CTSS model captured key neutrophil-dominant clinical and histopathological features associated with GPP patients. Mechanistically, CTSS promoted keratinocyte-mediated neutrophil recruitment via NF-κB and p38/MAPK signaling pathways, upregulating IL-8 and ICAM-1 expression. Notably, pharmacological inhibition of CTSS with LY3000328 significantly attenuated neutrophilic inflammation in vivo and in vitro. CONCLUSION CTSS functions as a critical amplifier of neutrophilic inflammation in GPP and represents a potential therapeutic target. The IMQ + CTSS mouse model provides a mechanistic platform for investigating neutrophilic inflammation and evaluating potential therapeutic strategies targeting CTSS in GPP.
Hepatic fibrosis is sustained by inflammation-driven hepatic stellate cells (HSCs) activation and is frequently accompanied by intestinal barrier disruption and gut microbial dysbiosis. 2,3,9,10-tetramethoxy-5,6-dihydroisoquinolino[3,2-a]isoquinolin-7-ium chloride (TDQ-Cl) is a quaternary isoquinoline alkaloid with anti-inflammatory activity and emerging hepatoprotective potential. This study investigated the hepatoprotective effects and underlying mechanisms of TDQ-Cl against hepatic fibrosis and associated intestinal injury. HSC-T6 and LX-2 were activated by transforming growth factor-β (TGF-β) and treated with TDQ-Cl, retinoic acid (RA), LG100268 or UVI 3003. RXRα-silenced LX-2 was stimulated with TGF-β and treated with TDQ-Cl. C57BL/6 J mice were intraperitoneally injected with thioacetamide (TAA), followed by TDQ-Cl, silymarin or RA administration. In activated HSCs, TDQ-Cl reduced extracellular matrix (ECM) accumulation, IL-6, cleaved caspase-1, mature IL-1β, and STAT3 phosphorylation while restoring RXRα expression. Cellular thermal shift assay showed increased thermal stability of RXRα following TDQ-Cl treatment. RXRα silencing exacerbated fibrotic responses and attenuated the inhibitory effects of TDQ-Cl on p-STAT3, α-SMA, and IL-6. Co-immunoprecipitation indicated that TDQ-Cl reduced the association between RXRα and phosphorylated STAT3. TDQ-Cl also attenuated conditioned-medium-induced LX-2 activation, accompanied by regulation of RXRα-STAT3 signaling. In TAA-induced mice, TDQ-Cl attenuated liver injury, ECM accumulation, inflammation, and hepatic STAT3 phosphorylation while restoring hepatic RXRα expression. TDQ-Cl also improved intestinal barrier integrity, reduced macrophage infiltration and STAT3 phosphorylation, restored colonic RXRα expression, and partially normalized TAA-associated gut microbial alterations. Collectively, these findings indicate that TDQ-Cl ameliorates hepatic fibrosis and associated intestinal injury through RXRα-STAT3-related inflammatory regulation, accompanied by partial normalization of gut microbial composition.
