YPL-001

Piscroside C, isolated from Pseudolysimachion rotundum var. subintegrum, is a novel iridoid glycoside with therapeutic efficacy in a mouse model of chronic obstructive pulmonary disease (COPD). Piscroside C has been reported as a constituent of YPL-001 (under Phase 2a study, ClinicalTrials.gov identifier NCT02272634).

To investigate the mechanisms behind piscroside C therapeutic effects on COPD in human airway epithelial NCI-H292 cells.

We tested if piscroside C effectively suppresses MUC5AC gene expression and TNF-RSC/IKK/NF-κB cascades in TNF-α-stimulated NCI-H292 cells by employing, reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, luciferase reporter assays, chromatin immunoprecipitation assays and immunoprecipitation.

Piscroside C markedly suppressed the expression of TNF-α-induced MUC5AC mucus protein by inhibiting the transcriptional activity of NF-κB in NCI-H292 cells. Indeed, piscroside C negatively regulated the function of TNF receptor 1 signaling complex (TNF-RSC, an upstream regulator of the NF-κB pathway) without affecting its extracellular interaction with the TNF-α ligand. This inhibitory effect by piscroside C is mediated by the inactivation of protein kinase C (PKC), an essential regulator of TNF-RSC. PKC inactivation by piscroside C results in decreased PKCδ binding to a TRAF2 subunit of TNF-RSC and subsequent reduced IKK phosphorylation, resulting in NF-κB inactivation.

We propose that piscroside C is a promising therapeutic constituent of YPL-001 through its inhibition of PKCδ activity in the TNF-RSC/IKK/NF-κB/MUC5AC signaling cascade.

Chronic obstructive pulmonary disease (COPD) is a major inflammatory lung disease characterized by irreversible and progressive airflow obstruction. Although corticosteroids are often used to reduce inflammation, steroid therapies are insufficient in patients with refractory COPD. Both serum amyloid A (SAA) and IL-33 have been implicated in the pathology of steroid-resistant lung inflammation. Picroside II isolated from Pseudolysimachion rotundum var. subintegrum (Plantaginaceae) is a major bioactive component of YPL-001, which has completed phase-2a clinical trials in chronic obstructive pulmonary disease patients. In this study, we investigated whether picroside II is effective in treating steroid refractory lung inflammation via the inhibition of the SAA-IL-33 axis. Picroside II inhibited LPS-induced SAA1 expression in human monocytes, which are resistant to steroids. SAA induced the secretion of IL-33 without involving cell necrosis. Picroside II, but not dexamethasone effectively inhibited SAA-induced IL-33 expression and secretion. The inhibitory effect by picroside II was mediated by suppressing the mitogen-activated protein kinase (MAPK) p38, ERK1/2, and nuclear factor-κB pathways. Our results suggest that picroside II negatively modulates the SAA-IL-33 axis that has been implicated in steroid-resistant lung inflammation. These findings provide valuable information for the development of picroside II as an alternative therapeutic agent against steroid refractory lung inflammation in COPD.