Role of TLR4-p38 MAPK-Hsp27 signal pathway in LPS-induced pulmonary epithelial hyperpermeability

Abstract

BackgroundThe breakdown of alveolar barrier dysfunction contributes to Lipopolysaccharide stimulated pulmonary edema and acute lung injury. Actin cytoskeleton has been implicated to be critical in regulation of epithelial barrier. Here, we performed in vivo and in vitro study to investigate role of TLR4-p38 MAPK-Hsp27 signal pathway in LPS-induced ALI.MethodsFor in vivo studies, 6–8-week-old C57 mice were used, Bronchoalveolar lavage Fluid /Blood fluorescent ratio, wet-to-dry lung weight ratio, as well as protein concentrations and neutrophil cell counts in BALF were detected as either directly or indirectly indicators of pulmonary alveolar barrier dysfunction. And hematoxylin and eosin staining was performed to estimate pulmonary injury. The in vitro explorations of transepithelial permeability were achieved through transepithelial electrical resistance measurement and testing of FITC-Dextran transepithelial flux in A549. In addition, cytoskeletal rearrangement was tested through F-actin immunostaining. And SB203580 was used to inhibit p38 MAPK activation, while siRNA was administered to genetically knockdown specific protein.ResultsWe showed that LPS triggered activation of p38 MAPK, rearrangement of cytoskeleton which resulted in severe epithelial hyperpermeability and lung edema. A549 pretreated with TLR4 siRNA、p38 MAPK siRNA and its inhibitor SB203580 displayed a lower permeability and fewer stress fibers formation after LPS stimulation, accompanied with lower phosphorylation level of p38 MAPK and Hsp27, which verified the involvement of TLR4-p38 MAPK-Hsp27 in LPS-evoked alveolar epithelial injury. Inhibition of p38 MAPK activity with SB203580 in vivo attenuated pulmonary edema formation and hyperpermeability in response to LPS.ConclusionsOur study demonstrated that LPS increased alveolar epithelial permeability both in vitro and in vivo and that TLR4- p38 MAPK- Hsp27 signal pathway dependent actin remolding was involved in this process.

α1AMP-Activated Protein Kinase Protects against Lipopolysaccharide-Induced Endothelial Barrier Disruption via Junctional Reinforcement and Activation of the p38 MAPK/HSP27 Pathway

“…However, the role of HSP27 in the regulation of endothelial permeability remains controversial. For example, HSP27 phosphorylation protects against hypoxia- or burn serum-induced permeability of endothelial cells [ 25 , 26 , 27 , 28 , 29 ]. On the contrary, pertussis toxin-induced endothelial permeability is temporally linked to p38 MAPK activation and phosphorylation of HSP27 [ 27 , 78 ]; and LPS-induced endothelial barrier dysfunction correlates with HSP27 phosphorylation in vitro (our own data) and in vivo [ 28 , 79 ].…”

“…HSP27 is phosphorylated by mitogen-activated protein kinase-activated protein kinases (MAPKAPK) 2 and 3, which are both direct substrates of p38 MAPK α and β [ 27 ]. The role of HSP27 phosphorylation in the regulation of endothelial permeability remains controversial [ 25 , 26 , 27 , 28 , 29 ]. In addition, small Rho GTPases are crucial orchestrators of actin organization and contractility [ 23 , 30 ].…”

Early progression of pulmonary hypertension in the monocrotaline model in males is associated with increased lung permeability

“…We have also found that heme induces disruptive barrier mechanisms leading to a reduction in tight junction (TJ) proteins ZO-1, and claudins1,5, which regulates fluid retention in the bloodstream by the endothelial barrier [32,33]. At the same time, we observed an increased actin stressfibers formation signaling via HSP27 and Rac1 [34,35]. All these events will ultimately lead to endothelial barrier leakage (Fig.…”

Baicalin Liposome Alleviates Lipopolysaccharide-Induced Acute Lung Injury in Mice via Inhibiting TLR4/JNK/ERK/NF-κB Pathway

“…The TLR4-NF- κ B signaling pathway plays an important role in the regulation of LPS-induced ALI [ 18 – 21 ]. MAPK signaling pathways are also important ways of TLR4 initiation [ 22 ], which are regulated by a characteristic phosphorelay system in which a series of protein kinases phosphorylate, such as JNK and ERK [ 23 ]. We detected some key proteins using western blot experiments to explore the mechanisms of BA treatment on ALI.…”