HIF expression in epithelial cells can control the release of chemoattractants that recruit neutrophils to the site of infection or inflammation. Dendritic cells (DCs) exposed to hypoxia upregulate genes coding for proteins

DNA Damage inhibitor chemotactic for neutrophils such as chemokine (C-X-C motif) ligand (CXCL)2, CXCL3, CXCL5, and CXCL8 [29]. HIF induces β2 integrin expression in neutrophils [30], and Cdc42 and Rac1 expression in macrophages [31], enhancing migration of both cell types to the site of infection. Hypoxia also increases CXC chemokine receptor (CXCR)4 [32] and inhibits CC chemokine receptor (CCR)5 [33] expression in macrophages in a HIF-dependent manner, which increases retention of macrophages at the site of infection. Not only are more immune cells recruited and retained, but those cells live longer. HIF extends the functional neutrophil lifespan by inhibiting apoptotic pathways in an NF-κB-dependent manner [34, 35]. People with mutations in vHL—and therefore constitutively elevated HIF levels—have neutrophils with longer lifespans. Hypoxia also promotes survival of monocytes and macrophages [36]. HIF

transcriptional regulation also supports other phenotypes related to immune cell activation. Hypoxia leads to TLR-2, TLR-4, and TLR-6 upregulation in a HIF-dependent manner Selleckchem Trametinib [37, 38], enhancing the detection of pathogen-associated molecular patterns. Hypoxic myeloid cells from mice exhibit increased phagocytosis [39], and those from humans who have mutations in vHL have increased phagocytic capacity as well [40]. In an in vivo model of innate infection, mice lacking HIF-1α in myeloid cells had diminished capacity to fight off a skin infection with the pathogen group A Streptococcus (GAS) [41]. Hif1a knockdown by siRNA also led to more severe corneal disease in mice infected intraocularly with Pseudomonas aeruginosa, and this effect GBA3 was due to impaired neutrophil function [42].

Conversely, mice in which HIF was elevated by drug treatment were better able to control skin infection by methicillin-resistant Staphylococcus aureus (MRSA) [43, 44]. Overall, augmenting HIF in macrophages increases bactericidal activity by increasing the production of a wide range of antimicrobial factors [43, 44]. Hypoxia leads myeloid cells to release more nitric oxide (NO), granule proteases, antimicrobial peptides, and proinflammatory cytokines [41, 45]. One notable exception is superoxide generation via the oxidative burst, which appears to transpire with equal efficiency in wild type and Hif1a null macrophages [41]. It is perhaps logical that the enzymatic pathway for superoxide generation is not elevated during hypoxia, given that it requires the presence of oxygen, which is by definition in short supply.