Epithelia-sensory neuron crosstalk underlies cholestatic itch induced by lysophosphatidylcholine

Yong Chen, Zi-Long Wang, Michele Yeo, Qiao-Juan Zhang, Ana E. López- Romero, Hui-Ping Ding, Xin Zhang, Qian Zeng, Sara L. Morales-Lázaro, Carlene Moore, Ying-Ai Jin, Huang-He Yang, Johannes Morstein, Andrey Bortsov, Marcin Krawczyk, Frank Lammert, Manal Abdelmalek, Anna Mae Diehl, Piotr Milkiewicz, Andreas E. Kremer, Jennifer Y. Zhang, Andrea Nackley, Tony E. Reeves, Mei- Chuan Ko, Ru-Rong Ji, Tamara Rosenbaum, Wolfgang Liedtke

BACKGROUND & AIMS

Limited understanding of pruritus mechanisms in cholestatic liver diseases hinders development of anti-pruritic treatments. Previous studies implicated lysophosphatidic acid (LPA) as a potential mediator of cholestatic pruritus.

METHODS

Pruritogenicity of LPC, LPA’s precursor, was examined in naïve mice, cholestatic mice, and nonhuman primates. LPC’s pruritogenicity involving keratinocyte-TRPV4 was studied using genetic and pharmacological approaches, cultured keratinocytes, ion channel physiology and structural-computational modeling. Activation of pruriceptor-sensory neurons by microRNA-146a (miR-146a), secreted from keratinocytes, was identified by in-vitro and ex-vivo Ca²⁺-imaging assays. Sera from primary biliary cholangitis (PBC) patients were used for measuring the levels of LPC and miR-146a.

RESULTS

LPC was robustly pruritic in mice. TRPV4 in skin keratinocytes was essential for LPC-induced itch and itch in mice with cholestasis. 3D-structural modeling, site-directed mutagenesis and channel function analysis suggested a TRPV4 C-terminal motif for LPC binding and channel activation. In keratinocytes, TRPV4-activation by LPC induced extracellular release of miR-146a, which activated TRPV1⁺-sensory neurons to cause itch. Both LPC and miR-146a levels were elevated in sera of PBC patients with itch and correlated with itch intensity. Moreover, LPC and miR-146a were also increased in sera of cholestatic mice and elicited itch in nonhuman primates.

CONCLUSIONS

We identified LPC as a novel cholestatic pruritogen that induces itch through epithelia-sensory neuron crosstalk, whereby it directly activates skin keratinocyte-TRPV4, which rapidly release miR-146a to activate skin-innervating TRPV1⁺-pruriceptor sensory neurons. Our findings support the new concept of the skin, as a sensory organ, playing a critical role in cholestatic itch, beyond liver, peripheral sensory neurons and central neural pathways supporting pruriception.