ITIH4 attenuates acute lung injury by Fe-containing particulate matter in mice via Hippo pathway in type II alveolar epithelial cells

Respir Res. 2025 May 28;26(1):201. doi: 10.1186/s12931-025-03256-z.

Abstract

Background: Metals in particulate matter (PM), like iron (Fe), were associated with lung injury. Inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4) was suggested to inhibit lung inflammation. However, the effect of metals in PM, particularly Fe, on lung inflammation involving ITIH4 remained unclear.

Methods: We investigated the effects of recombinant ITIH4 (rITIH4) against acute lung injury in C57BL/6JNarl and B6.Sftpc-CreERT2;Ai14(RCL-tdT)-D mice exposed to Fe-containing PM. Mice were exposed to diesel exhaust particles (DEP) or soluble iron (FeCl₃) via intratracheal instillation, while rITIH4 treatment was administered intranasally after exposure. Lung function, Fe levels (both bulk and single-cell by inductively-coupled plasma mass spectrometry (ICP-MS) and single-cell ICP-MS, respectively), inflammatory cell infiltration, and Hippo pathway regulation in type II alveolar epithelial cells (AECII) were assessed.

Results: We observed correlation between lung function changes and Fe levels, both in bulk and single-cell Fe in peripheral blood mononuclear cells. Single-cell RNA sequencing of the control group identified AECII-related cells characterized by high Sftpc, Sftpa1, Mzb1, B3 gnt5, Cacna1e, and Agbl1 expression. rITIH4 treatment in DEP-exposed mice restored Hippo pathway Cdh1, Itih4, Pdpn, Wwtr1, and Yap1 in AECII. rITIH4 reversed DEP- and Fe-induced increases in neutrophil infiltration, neutrophil-to-lymphocyte ratio, and monocyte depletion in bronchoalveolar lavage fluid (BALF). rITIH4 reduced BALF CXCL1/KC levels by DEP and serum 8-isoprostane levels by Fe. rITIH4 also reduced DEP-induced lung damage, increased ⍺-catenin and p-YAP in Fe-exposed mice, and pTAZ/TAZ ratio in both DEP- and Fe-exposed mice. rITIH4 increased pYAP/YAP ratio in DEP-exposed mice while decreasing LC3BII/I ratio in Fe-exposed mice.

Conclusion: ITIH4 attenuated acute lung injury in mice exposed to PM, specifically Fe, by modulating the Hippo pathway in AECII.

Keywords: Air pollution; Autophagy; Diesel exhaust particles; Inflammation; Single-cell analysis.

MeSH terms

  • Acute Lung Injury* / chemically induced
  • Acute Lung Injury* / metabolism
  • Acute Lung Injury* / pathology
  • Acute Lung Injury* / prevention & control
  • Alveolar Epithelial Cells* / drug effects
  • Alveolar Epithelial Cells* / metabolism
  • Alveolar Epithelial Cells* / pathology
  • Animals
  • Disease Models, Animal
  • Glycoproteins* / pharmacology
  • Hippo Signaling Pathway
  • Iron* / toxicity
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Particulate Matter* / toxicity
  • Protein Serine-Threonine Kinases* / metabolism
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Vehicle Emissions / toxicity

Substances

  • Protein Serine-Threonine Kinases
  • Particulate Matter
  • Iron
  • Glycoproteins
  • Vehicle Emissions