Perfluorocarbons Decrease Chlamydophila pneumoniae–Mediated Inflammatory Responses of Rat Type II Pneumocytes In Vitro

Abstract

Chlamydophila pneumoniae alter the expression of Toll-like receptor (TLR) 4 in alveolar type II (ATII)-cells. Subsequently nuclear factor kappaB (NF-B) is activated and tumor necrosis factor-␣ (TNF-␣) and macrophage inflammatory protein 2 (MIP-2) are produced. Perfluorocarbons (PFC) are beneficial in animals with bacterial pneumonia and reduce production of TNF-␣. Using isolated ATII-cells, it was studied whether PFC prevent C. pneumoniae-induced TNF-␣ and MIP-2 release and what the underlying pathway is. PF5080 preincubation prevented C. pneumoniae-induced secretion of TNF-␣ (43 Ϯ 10 versus 661 Ϯ 41 pg/mL) and MIP-2 (573 Ϯ 41 versus 4786 Ϯ 502 pg/mL). The C. pneumoniae-induced 2.2-fold increase of TNF-␣ Receptor 1 expression was reduced by PF5080. C. pneumoniae reduced cytoplasmatic IB␣ (3.7 Ϯ 0.3 versus 14 Ϯ 1) and increased NF-B p65 (31 Ϯ 7.5 versus 3.6 Ϯ 1.1) compared with control. PF5080 prevented NF-B activation. TLR4 expression was 1.5-fold higher after C. pneumoniae incubation, but remained at control levels after PF5080 pretreatment. After 24 h of C. pneumoniae incubation, in 88 Ϯ 6% of cells bacteria were found in the perinuclear region and in 50% of these cells bacteria adhered to cellular surface. After PF5080 preincubation, C. pneumoniae were in 32 Ϯ 4% attached to and in 5 Ϯ 1% internalized in ATII-cells. Since PF5080 was found in ATII-cell membranes, PF5080 effect could be explained by an alteration of the cellular membrane, preventing activation of the inflammatory cascade. Chlamydophila pneumoniae are obligate intracellular Gram-negative bacteria that cause respiratory infections in pediatric populations and adults (1,2). Recent studies demonstrated the presence of C. pneumoniae in alveolar macrophages and ATII cells in patients with chronic obstructive pulmonary disease (COPD) (3). Whereas most respiratory infections with C. pneumoniae are self-limited (4), bacterial colonization can lead to infectious exacerbations and development of COPD (5). Because detection rate of C. pneumonia varies significantly (6), the clinical relevance of C. pneumoniae is still controversial.The effect of C. pneumoniae on isolated ATII-cells is well characterized. C. pneumoniae inhibit the surfactant metabolism of ATII-cells after internalization (7). Many of C. pneumoniae-induced effects are mediated by cytokines. C. pneumoniae act at the ATII cell membrane to induce the expression of TLR4 (8). TLR signaling is partly mediated by the transcription factor NF-B, which controls the expression of many genes involved in the inflammatory response (9). C. pneumoniae-induced activation of NF-B leads to a release of the chemokine MIP-2 and the pro-inflammatory cytokine tumor necrosis factor alpha (TNF-␣) (8) and its receptor tumor necrosis factor receptor 1 (TNFR1). Together, they play an important role in bacterial infections and modulate the inflammatory process (10).PFC-administered as liquid (11), vapor (12), or gas (13) into the lung-represent an alternative approach to treat respiratory insufficiency. Intrat...

Cytoprotection of Perfluorocarbon on PMVECs In Vitro

“…Evidence for this barrier effect is supported by other studies [21,22]. Another mechanism implicated in the biological effects of PFC is related to the fact that PFC is able to partition into the lipid component of cellular membranes and the cytoplasm [23], where PFC can execute its nonspecific cell membrane stabilization by interfering with (1) the interaction between stimulant and receptor, (2) the transmembrane signal transduction, and (3) the transduction of intracellular signaling pathways [23][24][25]. So it can be assumed that PFC directly alters the cellular surface membrane, thereby reducing the intracellular signaling cascade and the subsequent inflammatory response.…”

The effects of perfluorocarbon on ICAM-1 expression in LPS-induced A549 cells and the potential mechanism

“…In recent years, the major studies regarding liquid ventilation have focused on animal experiments or in vitro experiments with few clinical trials. Based on these animal studies and cell experiments, liquid ventilation holds promise to improve low pulmonary compliance and gas exchange in addition to reducing pulmonary inflammatory responses, and ultimately improving the prognosis of animals with ARDS (6)(7)(8)(9)(10)(11)(12)(13)(14). However, the results of clinical randomized controlled trials (RCTs) and basic research have produced conflicting results, and the outlook of liquid ventilation has been disappointing.…”

“…The majority of patients require endotracheal intubation and positive pressure ventilation (1,2) and account for millions of days spent in intensive care units (5). In recent years, treatments of ALI/ARDS with improved efficacy have been sought, and studies have indicated that liquid ventilation with perfluorocarbon (PFC) compounds is a promising therapeutic approach (6)(7)(8)(9)(10)(11)(12)(13)(14). PFC is of interest for the treatment of ALI/ARDS due to the unique physicochemical properties, such as high solubility for oxygen, and the anti-inflammatory effects.…”

“…Liquid ventilation or aerosolized PFC has been demonstrated to improve gas exchange and improve pulmonary compliance compared with conventional mechanical ventilation in a variety of animal models of ALI/ARDS (6)(7)(8). Specifically, PFC has been shown to reduce levels of cytokines, chemokines and other mediators of pulmonary inflammation in both in vivo and in vitro models (9)(10)(11)(12)(13)(14). However, the understanding of the underlying mechanisms remains poor, in particular of the mechanisms associated with the PFC-induced anti-inflammatory effects.…”

Leukocyte antibacterial functions are not impaired by perfluorocarbon exposure in vitro

“…This proposition is supported by recent in vivo studies using aerosolized PFC in a surfactant-washout model that reported PFC to decrease mRNA expression of proinflammatory cytokines and adhesion molecules in lung tissue samples as well as in microdissected alveolar macrophages and pulmonary parenchymal cells (42,49,50). Further evidence for cellular anti-inflammatory effects of PFC is provided by in vitro experiments showing a decreased response of activated polymorphonuclear neutrophils (PMN) and monocytic cells in terms of cytokine secretion, chemotaxis, cyclooxygenase-2 (COX-2) expression, and NF-B activation (5,25,37,46,51). Liquid ventilation with PFC did not result in improved survival or reduced need for ventilatory support in recent multicenter trials of patients with acute respiratory distress syndrome (ARDS) (17,24).…”