The pseudoproteinase iRhom2 critically promotes acute lung inflammation

ADAM17 sheds cell surface molecules such as TNF-α, IL-6Rα and L-selectin. This activity requires either iRhom1 or iRhom2 as adapter molecules. Since iRhom2 is predominantly expressed in leukocytes and upregulated in tissue cells during inflammation, it represents a potential anti-inflammatory target. We therefore investigated the effects of iRhom2 deficiency in mice using in vivo, ex vivo, and in vitro models of acute inflammation.

In an in vivo model of LPS-induced lung inflammation, iRhom2 knockout mice showed reduced neutrophil recruitment into the bronchoalveolar space. Notably, the few recruited neutrophils remained L-selectin positive, whereas most neutrophils in wildtype mice were L-selectin negative, confirming that L-selectin shedding depends on the iRhom2/ADAM17 axis. Furthermore, it suggests that impaired shedding is associated with decreased neutrophil recruitment.

Additionally, ADAM17-dependent release of TNF-α and IL-6Rα into the alveolar space was diminished in the absence of iRhom2, accompanied by reduced expression of inflammatory mediators. In isolated perfused lungs challenged with LPS, iRhom2 deficiency similarly reduced inflammatory mediator production, indicating a role for iRhom2 in resident lung tissue cells during the initiation of inflammation.

To specifically assess immune cell responses, we further examined macrophages, the sole resident immune cells in the lung. In vitro, LPS-stimulated bone marrow derived macrophages lacking iRhom2 showed decreased shedding of TNF-α and IL-6Rα and reduced induction of secondary inflammatory mediators.

Thus, targeting iRhom2 effectively suppresses ADAM17-mediated inflammatory responses in the lung, while preserving basal ADAM17 activity through iRhom1, offering a more selective therapeutic strategy with fewer side effects.

Highlights

The ADAM17 adapter molecule iRhom2 is required for the acute lung inflammation of mice in vivo including cytokine response and neutrophil recruitment.

In resident lung tissue cells iRhom2 promotes the LPS induced inflammatory response at the alveolar interface.

In macrophages iRhom2 is required for an effective ADAM17 dependent inflammatory response to LPS.

Thus, iRhom2 targeting can serve to suppress inflammatory activities of ADAM17 in the lung.

Graphical Abstract

Schematic overview depicting the role of the iRhom2-ADAM17 axis in mediating neutrophil infiltration and cytokine release during induced pulmonary inflammation, serving as a model for acute lung injury (ALI).