NOD1 regulates leukocyte dynamics and inflammation in obesity-associated acute lung injury

Obesity is a chronic metabolic condition that alters innate immune responses, thereby modulating outcomes in inflammatory diseases such as acute lung injury (ALI). Nucleotide-binding oligomerization domain-containing protein 1 (NOD1) is a cytosolic pattern recognition receptor involved in bacterial sensing and inflammatory signaling. While NOD1 has been implicated in metabolic inflammation, its role in obesity-associated ALI remains unknown. Here, we investigated the impact of NOD1 deficiency on pulmonary inflammation in a model of LPS-induced ALI during obesity. Wild type (WT) and Nod1-/- female mice were fed a control or high-fat diet (HFD) for 10 weeks, followed by intranasal LPS administration and evaluation after 24 hours. In obese Nod1-/- mice, we observed reduced leukocyte and neutrophil recruitment to the bronchoalveolar lavage (BAL), accompanied by increased levels of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, IL-17A, IL-22), suggesting impaired neutrophil clearance. In the lung parenchyma, NOD1 deficiency during obesity led to elevated neutrophil accumulation, enhanced myeloperoxidase activity and expression, increased cellular senescence (SA-β-Gal), and reduced CD163⁺ macrophages, alongside a shift toward a pro-inflammatory, M1-like phenotype. Furthermore, Nod1-/- obese mice displayed enhanced NF-κB and ERK1/2 activation and reduced p38 phosphorylation. Gene expression analysis confirmed upregulation of chemokines, adhesion molecules, and inflammasome components, along with downregulation of M2 polarization markers. Our findings identify NOD1 as a modulator of leukocyte dynamics and inflammation during obesity-associated ALI. These results suggest NOD1’s protective role in regulating pulmonary immune responses under metabolic stress.