Substance P promotes liver fibrosis by keeping scar-producing cells active while accelerating aging in bile duct cells, and blocking its receptor reduced fibrosis in mice.
Fibrosis reduced in 2 mouse modelsBoth NK-1R knockout and NK-1R antagonist treatment significantly decreased liver fibrosis markers in cholestatic injury models
What the researchers found
Substance P drives liver fibrosis during cholestatic liver injury by acting through the neurokinin-1 receptor (NK-1R). Knocking out NK-1R in mice or blocking it with the antagonist L-733,060 significantly reduced liver fibrosis, as shown by decreased sirius red staining, lower fibrosis gene expression, and reduced TGF-β1 levels in serum.
The mechanism involves a dual effect on cellular senescence: Substance P decreases senescence in hepatic stellate cells (keeping them active and fibrosis-promoting) while increasing senescence in cholangiocytes (bile duct cells). Blocking NK-1R reversed both of these effects. Human tissue from primary sclerosing cholangitis patients also showed elevated expression of Substance P and NK-1R compared to healthy controls.
Why it matters
Liver fibrosis is a major driver of chronic liver disease progression, and current treatments are limited. This study identifies the Substance P/NK-1R signaling pathway as a potential therapeutic target — and an NK-1R antagonist (L-733,060) already reduced fibrosis in two different mouse models. The fact that human liver tissue from primary sclerosing cholangitis patients showed the same elevated SP/NK-1R expression suggests this pathway is clinically relevant.
The numbers in context
NK-1R knockout reduced BDL-induced fibrosis · L-733,060 reduced fibrosis in Mdr2−/− mice · decreased sirius red staining · reduced TGF-β1 levels · elevated SP/NK-1R in human PSC tissue
How the study worked
Researchers used multiple mouse models: wild-type and NK-1R knockout mice that underwent bile duct ligation (BDL) or sham surgery, and Mdr2 knockout mice treated with either the NK-1R antagonist L-733,060 or saline. Wild-type mice were also treated with Substance P or saline. Liver fibrosis was measured by sirius red staining, fibrosis gene/protein expression, and TGF-β1 levels. Cellular senescence was assessed in hepatic stellate cells and cholangiocytes. Human liver tissue from primary sclerosing cholangitis patients was also analyzed.
Who was studied
Mouse models (wild-type, NK-1R knockout, Mdr2 knockout) and human liver tissue from primary sclerosing cholangitis patients
What this study cannot tell us
This is primarily an animal study using mouse models, so results may not fully translate to human liver disease. While human PSC tissue showed elevated SP/NK-1R expression, no therapeutic interventions were tested in human subjects. The NK-1R antagonist L-733,060 has not been evaluated in clinical trials for liver fibrosis.
How to read the evidence
This is a well-designed animal study using multiple mouse models (knockout and pharmacological) with corroborating human tissue data. However, no clinical trials have tested NK-1R antagonists for liver fibrosis in humans, keeping the evidence at a moderate level.
When this study was published
Published in 2017 in Hepatology, a leading liver disease journal. The SP/NK-1R axis in liver fibrosis remains an active area of preclinical research.
The bigger picture
This study adds Substance P to the growing list of neuropeptides that influence organ fibrosis beyond their traditional roles in pain and inflammation. If NK-1R antagonists — some of which already exist as approved drugs for other conditions — prove effective against liver fibrosis in humans, it could open a repurposing pathway for treating chronic liver disease.
Questions still open
- Could existing NK-1R antagonist drugs (like aprepitant, used for nausea) be repurposed to treat liver fibrosis in humans?
- Does Substance P drive fibrosis in other organs through the same dual-senescence mechanism?
- What is the optimal timing for NK-1R blockade — can it reverse established fibrosis or only prevent new scarring?
Common questions
What does Substance P do to the liver?
Could blocking Substance P's receptor treat liver disease?
Read the original research
Substance P increases liver fibrosis by differential changes in senescence of cholangiocytes and hepatic stellate cells.
Hepatology (Baltimore, Md.), 66(2), 528-541
Citation
Wan, Ying; Meng, Fanyin; Wu, Nan; Zhou, Tianhao; Venter, Julie; Francis, Heather; Kennedy, Lindsey; Glaser, Trenton; Bernuzzi, Francesca; Invernizzi, Pietro; Glaser, Shannon; Huang, Qiaobing; Alpini, Gianfranco. (2017). Substance P increases liver fibrosis by differential changes in senescence of cholangiocytes and hepatic stellate cells.. Hepatology (Baltimore, Md.), 66(2), 528-541. https://doi.org/10.1002/hep.29138