Interleukin‐8 (IL‐8) has been implicated in the pathogenesis of several human respiratory diseases, including tuberculosis (TB). Importantly and in direct relevance to the objectives of this report quite a few findings suggest that the presence of IL‐8 may be beneficial for the host. IL‐8 may aid with mounting an adequate response during infection with Mycobacterium tuberculosis (M. tb); however, the underlying mechanism remains largely unknown. The major goal of our study was to investigate the contribution of IL‐8 to the inflammatory processes that are typically elicited in patients with TB. We have shown for the first time that IL‐8 can directly bind to tubercle bacilli. We have also demonstrated that association of IL‐8 with M. tb molecules leads to the augmentation of the ability of leukocytes (neutrophils and macrophages) to phagocyte and kill these bacilli. In addition, we have shown that significant amount of IL‐8 present in the blood of TB patients associates with erythrocytes. Finally, we have noted that IL‐8 is the major chemokine responsible for recruiting T lymphocytes (CD3⁺, CD4⁺, and CD8⁺ T cells). In summary, our data suggest that the association of IL‐8 with M. tb molecules may modify and possibly enhance the innate immune response in patients with TB.

Infection with seasonal influenza A virus (IAV) leads to lung inflammation and respiratory failure, a main cause of death in influenza-infected patients. Previous experiments in our laboratory indicate that Bruton’s tyrosine kinase (Btk) plays a substantial role in regulating inflammation in the respiratory region during acute lung injury in mice; therefore, we sought to determine if blocking Btk activity has a protective effect in the lung during influenza-induced inflammation. The Btk inhibitor ibrutinib (also known as PCI-32765) was administered intranasally to mice starting 72 h after lethal infection with IAV. Our data indicate that treatment with the Btk inhibitor not only reduced weight loss and led to survival, but also had a dramatic effect on morphological changes to the lungs, in IAV-infected mice. Attenuation of lung inflammation indicative of acute lung injury, such as alveolar hemorrhage, interstitial thickening, and the presence of alveolar exudate, together with reduced levels of the inflammatory mediators TNFα, IL-1β, IL-6, KC, and MCP-1, strongly suggests amelioration of the pathological immune response in the lungs to promote resolution of the infection. Finally, we observed that blocking Btk specifically in the alveolar compartment led to significant attenuation of neutrophil extracellular traps released into the lung in vivo and neutrophil extracellular trap formation in vitro. Our innovative findings suggest that Btk may be a new drug target for influenza-induced lung injury, and, in general, that immunomodulatory treatment may be key in treating lung dysfunction driven by excessive inflammation.

Helicobacter pylori colonizes the human gastric mucosa, causing chronic inflammation, peptic ulcers and gastric cancer. A cascade of harmful processes results from the interaction of these bacteria with the gastric epithelium. To investigate these processes in terms of upregulation of oxidative stress and cell apoptosis and downregulation of the pro-regenerative activity of cells. We employed an in vivo guinea pig model at 7 or 28 days postinoculation with H. pylori, corresponding to an acute or chronic stage of infection, respectively, and an in vitro model of guinea pig primary gastric epithelial cells and fibroblasts treated with bacterial components: glycine acid extract (GE), urease subunit A (UreA), cytotoxin-associated gene A protein (CagA) and lipopolysaccharide (LPS). Cells were evaluated for metabolic activity (MTT reduction), myeloperoxidase (MPO) and metalloproteinase (MMP-9) secretion, lipid peroxidation (4-hydroxynonenal (4HNE)), migration (wound healing), proliferation (Ki-67 antigen) and cell apoptosis (TUNEL assay; Bcl-xL, Bax, Bcl-2 expression; caspase 3 cleavage). Significant infiltration of the gastric mucosa by inflammatory cells in vivo in response to H. pylori was accompanied by oxidative stress and cell apoptosis, which were more intense 7 than 28 days after inoculation. The increase in cell proliferation was more intense in chronic than acute infection. H. pylori components GE, CagA, UreA, and LPS upregulated oxidative stress and apoptosis. Only H. pylori LPS inhibited cell migration and proliferation, which was accompanied by the upregulation of MMP-9. H. pylori infection induces cell apoptosis in conjunction with increased oxidative stress. Elevated apoptosis protects against deleterious inflammation and neoplasia; however, it reduces cell integrity. Upregulation of cell migration and proliferation in response to injury in the milieu of GE, CagA or UreA facilitates tissue regeneration but increases the risk of neoplasia. By comparison, downregulation of cell regeneration by H. pylori LPS may promote chronic inflammation.

Staphylococcus aureus causes life-threatening pneumonia in hospitals and deadly superinfection during viral influenza. The current study investigated the role of surfactant protein A (SP-A) in opsonization and clearance of S. aureus. Previous studies showed that SP-A mediates phagocytosis via the SP-A receptor 210 (SP-R210). Here, we show that SP-R210 mediates binding and control of SP-A-opsonized S. aureus by macrophages. We determined that SP-A binds S. aureus through the extracellular adhesin Eap. Consequently, SP-A enhanced macrophage uptake of Eap-expressing (Eap⁺) but not Eap-deficient (Eap⁻) S. aureus. In a reciprocal fashion, SP-A failed to enhance uptake of Eap⁺ S. aureus in peritoneal Raw264.7 macrophages with a dominant negative mutation (SP-R210(DN)) blocking surface expression of SP-R210. Accordingly, WT mice cleared infection with Eap⁺ but succumbed to sublethal infection with Eap- S. aureus. However, SP-R210(DN) cells compensated by increasing non-opsonic phagocytosis of Eap⁺ S. aureus via the scavenger receptor scavenger receptor class A (SR-A), while non-opsonic uptake of Eap⁻ S. aureus was impaired. Macrophages express two isoforms: SP-R210_L and SP-R210_S. The results show that WT alveolar macrophages are distinguished by expression of SP-R210_L, whereas SR-A^−/− alveolar macrophages are deficient in SP-R210_L expressing only SP-R210_S. Accordingly, SR-A^−/− mice were highly susceptible to both Eap⁺ and Eap⁻ S. aureus. The lungs of susceptible mice generated abnormal inflammatory responses that were associated with impaired killing and persistence of S. aureus infection in the lung. In conclusion, alveolar macrophage SP-R210_L mediates recognition and killing of SP-A-opsonized S. aureus in vivo, coordinating inflammatory responses and resolution of S. aureus pneumonia through interaction with SR-A.

A significant fraction of IL-8 in lung fluids from patients with the acute lung injury (ALI) is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 complexes), and lung fluid concentrations of these complexes correlate with development and outcome of ALI. In this study, we examined whether anti-IL-8:IL-8 complexes exhibit proinflammatory activity in vitro. These complexes were purified from pulmonary edema fluid samples obtained from patients with ALI. First, we found that IL-8 bound to the autoantibody retained its ability to trigger chemotaxis of neutrophils, whereas control antibody did not have significant chemotactic activity. Next, we examined the ability of anti-IL-8:IL-8 complexes to induce neutrophil activation, i.e., neutrophil respiratory burst and degranulation. Anti-IL-8:IL-8 complexes triggered superoxide and myeloperoxidase release from human neutrophils, and in contrast, the control antibody had no effect. We also demonstrated that IgG receptor, FcγRIIa, is the receptor involved in cellular activation mediated by these complexes. Blockade of FcγRIIa completely reverses activity of the complexes with the exception of chemotaxis. Both FcγRIIa and IL-8 receptors mediate chemotactic activity of anti-IL-8:IL-8 complexes, with FcγRIIa being, however, a predominant receptor. Furthermore, activity of the complexes is partially dependent on the activation of the mitogen-activated protein kinases, i.e., ERK and p38, important components of the FcγRIIa signaling cascade. Anti-IL-8:IL-8 complexes may therefore be involved in the pathogenesis of lung inflammation in clinical acute lung injury.

Previous observations made by our laboratory indicate that Bruton's tyrosine kinase (Btk) may play an important role in the pathophysiology of local inflammation in acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). We have shown that there is cross talk between FcγRIIa and TLR4 in alveolar neutrophils from patients with ALI/ARDS and that Btk mediates the molecular cooperation between these two receptors. To study the function of Btk in vivo we have developed a unique two-hit model of ALI: LPS/immune complex (IC)-induced ALI. Furthermore, we conjugated F(ab)₂fragments of anti-neutrophil antibodies (Ly6G1A8) with specific siRNA for Btk to silence Btk specifically in alveolar neutrophils. It should be stressed that we are the first group to perform noninvasive transfections of neutrophils, both in vitro and in vivo. Importantly, our present findings indicate that silencing Btk in alveolar neutrophils has a dramatic protective effect in mice with LPS/IC-induced ALI, and that Btk regulates neutrophil survival and clearance of apoptotic neutrophils in this model. In conclusion, we put forward a hypothesis that Btk-targeted neutrophil specific therapy is a valid goal of research geared toward restoring homeostasis in lungs of patients with ALI/ARDS.