RESUMO
Adenoviral vectors expressing Cre recombinase are commonly used to initiate tumor formation in murine lung cancer models. While these vectors are designed to target genetic recombination to lung epithelial cells, adenoviruses can infect additional cell types that potentially influence tumor development. Our goal was to explore the consequences of adenoviral-mediated alveolar macrophage (AM) transduction in a Kras-initiated lung tumor model. As expected, treatment of animals harboring the KrasLSL-G12D allele and an inducible green fluorescence protein (GFP) tracking allele with an adenoviral vector expressing Cre recombinase under the control of the cytomegalovirus (CMV) promoter (Ad5-CMV-Cre), caused GFP-positive lung adenocarcinomas. Surprisingly, however, up to 70% of the total GFP+ cells were AM, and GFP+ AM could be detected 6 months after tumor initiation, and transduced AM demonstrated Kras activation and increased proliferation. In contrast, recombination was not detected in other immune cell populations and AM recombination could be eliminated by tumor initiation with an adenovirus expressing Cre recombinase under the control of the surfactant protein C (SPC) promoter. In addition, AM isolated from KrasLSL-G12D animals and transduced by Ad5-CMV-Cre ex vivo displayed prolonged survival in vitro and increased the growth of murine lung adenocarcinoma CMT/167 cells when co-injected in an orthotopic flank model. Given the importance of the immune system in tumor development and progression, inadvertent AM transduction by Ad5-CMV-Cre merits careful consideration during lung cancer model selection particularly if studies evaluating the tumor-immune interactions are planned.
RESUMO
The group IVA calcium-dependent cytosolic phospholipase A2 (cPLA2α) enzyme directs a complex "eicosanoid storm" that accompanies the tissue response to injury. cPLA2α and its downstream eicosanoid mediators are also implicated in the pathogenesis of fibrosis in many organs, including the kidney. We aimed to determine the role of cPLA2α in bone marrow-derived cells in a murine model of renal fibrosis, unilateral ureteral obstruction (UUO). WT C57BL/6J mice were irradiated and engrafted with donor bone marrow from either WT mice [WT-bone marrow transplant (BMT)] or mice deficient in cPLA2α (KO-BMT). After full engraftment, mice underwent UUO and kidneys were collected 3, 7, and 14 days after injury. Using picrosirius red, collagen-3, and smooth muscle α actin staining, we determined that renal fibrosis was significantly attenuated in KO-BMT animals as compared with WT-BMT animals. Lipidomic analysis of homogenized kidneys demonstrated a time-dependent upregulation of pro-inflammatory eicosanoids after UUO; KO-BMT animals had lower levels of many of these eicosanoids. KO-BMT animals also had fewer infiltrating pro-inflammatory CD45+CD11b+Ly6Chi macrophages and reduced message levels of pro-inflammatory cytokines. Our results indicate that cPLA2α and/or its downstream mediators, produced by bone marrow-derived cells, play a major role in eicosanoid production after renal injury and in renal fibrinogenesis.