Improvement in insulin sensitivity and prevention of high fat diet-induced liver pathology using a CXCR2 antagonist

Background

Liver pathology (LP) characteristic of non-alcoholic fatty acid disease (NAFLD)/non-alcoholic steatohepatitis (NASH) is a prevalent co-morbidity of type 2 diabetes (T2D). Accumulating evidence indicates that neutrophils driving insulin resistance (IR), including hepatic IR, precipitate T2D-associated NAFLD/NASH. We hypothesized that targeting neutrophil accumulation into insulin-sensitive tissues in mice using a CXCR2 antagonist under T2D-precipitating high fat diet (HFD) could improve insulin sensitivity and prevent the progression towards liver pathology reminiscent of NAFLD/NASH.

Methods

Mice were age-matched and on standard rodent chow prior to 1:1 randomization into control and HFD formulated with the CXCR2 antagonist AZD5069 or with biologically inactive substitute. They were monitored for metabolic changes including insulin sensitivity using the hyperinsulinemic-euglycemic clamp and hepatic histopathologic evaluation in H&E-stained sections as well as via immunofluorescence microscopy of liver sections for leukocyte markers, collagen 1A1 formation, α-smooth muscle actin (SMA), and galectin-3 expression, for 16 weeks. Statistical tests used to determine significant differences among study groups and outcomes include Student’s t-test, one-way ANOVA, repeated measures two-way ANOVA, and Fisher’s exact test, depending on the analytical question.

Results

Compared to mice on HFD, mice in the AZD5069-formulated HFD exhibited improved insulin sensitivity, a modest reduction in weight gain, and a significant improvement in LP and markers related to NAFLD/NASH. Mice in the AZD5069-formulated HFD also exhibited reduced neutrophil accumulation into the liver at the end of the 16 week study period.

Conclusions

These results show, for the first time, the effectiveness of a selective CXCR2 antagonist to improve insulin sensitivity, concomitantly preventing the progression towards LP characteristic of NAFLD/NASH. This represents a novel approach to target IR and developing LP under T2D-susceptible conditions using a single agent. Furthermore, our data extend the growing evidence in support of neutrophils as a leukocyte population that imprints and maintains a chronic inflammatory state in the progression of dysregulated metabolism in liver-specific co-morbid conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01564-y.

CXCR2 Mediates Distinct Neutrophil Behavior in Brain Metastatic Breast Tumor

Brain metastasis is one of the main causes of mortality among breast cancer patients, but the origins and the mechanisms that drive this process remain poorly understood. Here, we report that the upregulation of certain CXCR2-associated ligands in the brain metastatic variants of the breast cancer cells (BrM) dynamically activate the corresponding CXCR2 receptors on the neutrophils, thereby resulting in the modulation of certain key functional neutrophil responses towards the BrM. Using established neutrophil-tumor biomimetic co-culture models, we show that the upregulation of CXCR2 increases the recruitment of Tumor-Associated Neutrophils (TANs) towards the BrM, to enable location-favored formation of Neutrophil Extracellular Traps (NETs). Inhibition of CXCR2 using small molecule antagonist AZD5069 reversed this behavior, limiting the neutrophil responses to the BrM and retarding the reciprocal tumor development. We further demonstrate that abrogation of NETs formation using Neutrophil Elastase Inhibitor (NEI) significantly decreases the influx of neutrophils towards BrM but not to their parental tumor, suggesting that CXCR2 activation could be used by the brain metastatic tumors as a mechanism to program the tumor-infiltrating TANs into a pro-NETotic state, so as to assume a unique spatial distribution that assists in the subsequent migration and invasion of the metastatic tumor cells. This new perspective indicates that CXCR2 is a critical target for suppressing neutrophilic inflammation in brain metastasis.

Distinct Spatio-Temporal Dynamics of Tumor-Associated Neutrophils in Small Tumor Lesions

Across a majority of cancer types tumor-associated neutrophils (TAN) are linked with poor prognosis. However, the underlying mechanisms, especially the intratumoral behavior of TAN, are largely unknown. Using intravital multiphoton imaging on a mouse model with neutrophil-specific fluorescence, we measured the migration of TAN in distinct compartments of solid tumor cell lesions in vivo. By longitudinally quantifying the infiltration and persistence of TAN into growing tumors in the same animals, we observed cells that either populated the peripheral stromal zone of the tumor (peritumoral TAN) or infiltrated into the tumor core (intratumoral TAN). Intratumoral TAN showed prolonged tumor-associated persistence and reduced motility compared to peritumoral TAN, whose velocity increased with tumor progression. Selective pharmacological blockade of CXCR2 receptors using AZD5069 profoundly inhibited recruitment of TAN into peritumoral regions, while intratumoral infiltration was only transiently attenuated and rebounded at later time points. Our findings unravel distinct spatial dynamics of TAN that are partially and differentially regulated via the CXCR2 signaling pathway.