calpain and Acute-Lung-Injury

Acute lung injury (ALI) is characterized by lung vascular endothelial cell (EC) barrier compromise resulting in increased endothelial permeability and pulmonary edema. The infection of gram-negative bacteria that produce toxins like LPS is one of the major causes of ALI. LPS activates Toll-like receptor 4, leading to cytoskeleton reorganization, resulting in lung endothelial barrier disruption and pulmonary edema in ALI. However, the signaling pathways that lead to the cytoskeleton reorganization and lung microvascular EC barrier disruption remain largely unexplored. Here we show that LPS induces calpain activation and talin cleavage into head and rod domains and that inhibition of calpain attenuates talin cleavage, RhoA activation, and pulmonary EC barrier disruption in LPS-treated human lung microvascular ECs

Topics: Acute Lung Injury; Calpain; Capillary Permeability; Humans; Lipopolysaccharides; Lung; Myosin Light Chains; Pulmonary Edema; Talin

Verdiperstat, a myeloperoxidase (MPO) inhibitor, is a well-known drug used for the treatment of multisystem atrophy. However, its therapeutic effect on acute lung injury (ALI) remains to be elucidated. In this study, the effect of verdiperstat on lipopolysaccharide (LPS)-induced two-hit rat ALI model was studied in vivo. Subsequently, to explore the anti-ALI mechanism of verdiperstat, an LPS-induced injury in human pulmonary microvascular endothelial cells (HMs) was studied in vitro. The continuous administration of verdiperstat at 120 mg/kg for 3 days exerted a protective effect on the LPS-induced two-hit rat ALI model, as reflected by the change in the lung coefficient and lung pathology scores from 0.72 to 0.61 and 6.08 to 4.37, respectively. Furthermore, the values of protective adhesion protein VE-cadherin and tight junction protein claudin 5 changed from 0.42 to 0.97 and 0.25 to 0.72, but MPO, the ratio of N-μ-calpain to μ-calpain, and the distribution of β-catenin in the nucleus changed from 3.04 to 2.17, 0.62 to 0.38 and 2.25 to 0.76, respectively. LPS-induced HMs in vitro also showed similar results, including lower MPO and the distribution of β-catenin in the nucleus, but higher VE-cadherin claudin 5 and N-μ-calpain. Moreover, MPO inhibition resulted in lower μ-calpain activation and lower β-catenin in the nucleus. Our cumulative results suggest that verdiperstat alleviates ALI by strengthening VE-cadherin and claudin 5 through the inhibition of MPO/μ-calpain/β-catenin activation.

Topics: Acute Lung Injury; Animals; beta Catenin; Calpain; Claudin-5; Endothelial Cells; Enzyme Inhibitors; Lipopolysaccharides; Lung; Peroxidase; Rats

Pulmonary microvascular endothelial cells (PMECs) injury including apoptosis plays an important role in the pathogenesis of acute lung injury during sepsis. Our recent study has demonstrated that calpain activation contributes to apoptosis in PMECs under septic conditions. This study investigated how calpain activation mediated apoptosis and whether heat stress regulated calpain activation in lipopolysaccharides (LPS)-stimulated PMECs. In cultured mouse primary PMECs, incubation with LPS (1 μg/ml, 24 h) increased active caspase-3 fragments and DNA fragmentation, indicative of apoptosis. These effects of LPS were abrogated by pre-treatment with heat stress (43 °C for 2 h). LPS also induced calpain activation and increased phosphorylation of p38 MAPK. Inhibition of calpain and p38 MAPK prevented apoptosis induced by LPS. Furthermore, inhibition of calpain blocked p38 MAPK phosphorylation in LPS-stimulated PMECs. Notably, heat stress decreased the protein levels of calpain-1/2 and calpain activities, and blocked p38 MAPK phosphorylation in response to LPS. Additionally, forced up-regulation of calpain-1 or calpain-2 sufficiently induced p38 MAPK phosphorylation and apoptosis in PMECs, both of which were inhibited by heat stress. In conclusion, heat stress prevents LPS-induced apoptosis in PMECs. This effect of heat stress is associated with down-regulation of calpain expression and activation, and subsequent blockage of p38 MAPK activation in response to LPS. Thus, blocking calpain/p38 MAPK pathway may be a novel mechanism underlying heat stress-mediated inhibition of apoptosis in LPS-stimulated endothelial cells.

Topics: Acute Lung Injury; Animals; Apoptosis; Calpain; Caspase 3; Cell Line; Down-Regulation; Endothelial Cells; Female; Heat-Shock Response; Hemangioendothelioma; Hot Temperature; Lipopolysaccharides; Lung; Male; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Microvessels; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Sepsis; Up-Regulation