Different mechanism of LPS-induced calcium increase in human lung epithelial cell and microvascular endothelial cell: a cell culture study in a model for ARDS

Calcium-sensing receptor regulates the angiogenic differentiation of LPS-treated human dental pulp cells via the phosphoinositide 3-kinase/Akt pathway in vitro

AIM

The purpose of this study was to investigate the role of calcium-sensing receptor (CaSR) in the angiogenic differentiation of lipopolysaccharide (LPS)-treated human dental pulp cells (hDPCs).

METHODOLOGY

The LPS-induced hDPCs were cultured in the medium with different combinations of CaSR agonist R568 and antagonist Calhex231. The cell proliferation, migration, and angiogenic capacity were measured by Cell Counting Kit-8 (CCK-8), scratch wound healing, and tube formation assays, respectively. Enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were conducted to determine the gene/protein expression of CaSR, inflammatory mediators, and angiogenic-associated markers. The activation of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt) was assessed by western blot analysis.

RESULTS

The cell proliferation was elevated in response to R568 or Calhex231 exposure, but an enhanced cell migration was only found in cultures supplemented with Calhex231. Furthermore, R568 was found to potentiate the formation of vessel-like structure, up-regulated the protein expression of tumour necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF), and stromal cell-derived factor (SDF)-1; comparable influences were also observed in R568-stimulated cells in the presence of PI3K inhibitor LY294002. In contrast, Calhex231 obviously inhibited the tube formation and VEGF protein level, whereas promoted the production of IL-6, TNF-α, and eNOS; however, in the presence of LY294002, Calhex231 showed a significant promotion on the protein expression of CaSR, VEGF, and SDF-1. In addition, R568 exhibited a promotive action on the Akt phosphorylation, which can be reversed by LY294002.

CONCLUSIONS

Our results demonstrated that CaSR can regulate the angiogenic differentiation of LPS-treated hDPCs with an involvement of the PI3K/Akt signalling pathway.

Augmentation of Endothelial S1PR1 Attenuates Postviral Pulmonary Fibrosis

Respiratory viral infections are frequent causes of acute respiratory distress syndrome (ARDS), a disabling condition with a mortality of up to 46%. The pulmonary endothelium plays an important role in the development of ARDS as well as the pathogenesis of pulmonary fibrosis; however, the therapeutic potential to modulate endothelium-dependent signaling to prevent deleterious consequences has not been well explored. Here, we used a clinically relevant influenza A virus infection model, endothelial cell-specific transgenic gain-of-function and loss-of-function mice as well as pharmacologic approaches and in vitro modeling, to define the mechanism by which S1PR1 expression is dampened during influenza virus infection and determine whether therapeutic augmentation of S1PR1 has the potential to reduce long-term postviral fibrotic complications. We found that the influenza virus-induced inflammatory milieu promoted internalization of S1PR1, which was pharmacologically inhibited with paroxetine, an inhibitor of GRK2. Moreover, genetic overexpression or administration of paroxetine days after influenza virus infection was sufficient to reduce postviral pulmonary fibrosis. Taken together, our data suggest that endothelial S1PR1 signaling provides critical protection against long-term fibrotic complications after pulmonary viral infection. These findings support the development of antifibrotic strategies that augment S1PR1 expression in virus-induced ARDS to improve long-term patient outcomes.

TNFα Enhances Calcium Influx by Interacting with AMPA Receptors in the Spinal Dorsal Horn Neurons

Tumor necrosis factor alpha (TNFα) is a proinflammatory cytokine and has been implicated in pain regulation. Neuronal activity in the spinal dorsal horn contributes to nociceptive transmission. However, it is not fully understood how TNFα affects the activity of spinal dorsal horn neurons. In the present study, we used calcium imaging to characterize the mechanism by which TNFα regulates calcium influx in the cultured spinal dorsal horn neurons. We observed that TNFα incubation caused an increase in fluorescent intensity of Fura-2, a specific intracellular calcium indicator, in the cultured spinal dorsal horn neurons, and such effect was significantly inhibited by co-incubation with R7050, a selective TNFα receptor antagonist, which suggests that TNFα can enhance calcium influx and increase neuronal activity via activating TNFα receptors in the spinal dorsal horn. Using double immunofluorescence staining, we showed that TNFα receptors were co-expressed with a-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor subunit GluA1 in the spinal dorsal horn neurons. We further observed that treatment with 1-naphthyl acetyl spermine (NASPM), a specific calcium-permeable AMPA receptor blocker, completely blocked the effect of TNFα incubation on calcium influx in the cultured neurons. Moreover, lipopolysaccharide (LPS)-induced calcium influx was inhibited by co-incubation with R7050. Together, our results suggest that TNFα in the spinal dorsal horn can increase calcium-indicated neuronal activity through the interaction between its receptor and calcium-permeable AMPA receptors.

Combination therapy of insulin-like growth factor I and BTP-2 markedly improves lipopolysaccharide-induced liver injury in mice

Acute liver injury is a common disease without effective therapy in humans. We sought to evaluate a combination therapy of insulin-like growth factor 1 (IGF-I) and BTP-2 in a mouse liver injury model induced by lipopolysaccharide (LPS). We chose this model because LPS is known to increase the expression of the transcription factors related to systemic inflammation (i.e., NFκB, CREB, AP1, IRF 3, and NFAT), which depends on calcium signaling. Notably, these transcription factors all have pleiotropic effects and account for the other observed changes in tissue damage parameters. Additionally, LPS is also known to increase the genes associated with a tissue injury (e.g., NGAL, SOD, caspase 3, and type 1 collagen) and systemic expression of pro-inflammatory cytokines. Finally, LPS compromises vascular integrity. Accordingly, IGF-I was selected because its serum levels were shown to decrease during systemic inflammation. BTP-2 was chosen because it was known to decrease cytosolic calcium, which is increased by LPS. This current study showed that IGF-I, BTP-2, or a combination therapy significantly altered and normalized all of the aforementioned LPS-induced gene changes. Additionally, our therapies reduced the vascular leakage caused by LPS, as evidenced by the Evans blue dye technique. Furthermore, histopathologic studies showed that IGF-I decreased the proportion of hepatocytes with ballooning degeneration. Finally, IGF-I also increased the expression of the hepatic growth factor (HGF) and the receptor for the epidermal growth factor (EGFR), markers of liver regeneration. Collectively, our data suggest that a combination of IGF-I and BTP-2 is a promising therapy for acute liver injury.

Effect of Dihydropyridine Calcium Channel Blocker on Mortality of Hypertension Patients With Moderate-Severe Pulmonary Acute Respiratory Distress Syndrome: A Multicenter Retrospective Observational Cohort Study

The aim was to evaluate the effect of dihydropyridine calcium channel blocker on the prognosis for moderate-severe pulmonary acute respiratory distress syndrome in hypertension patients.

DESIGN

A retrospective, observational, multicenter cohort study.

SETTING

A total of 307 patients without propensity score matching and 186 adult inpatients with propensity score matching diagnosed with hypertension and moderate-severe pulmonary acute respiratory distress syndrome in five teaching hospitals in Jiangsu province, China, from December 2015 to December 2020 were enrolled.

PATIENTS

A total of 307 patients without propensity score matching and 186 patients with propensity score matching diagnosed with hypertension and moderate-severe pulmonary acute respiratory distress syndrome were included in the final analysis.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic characteristics and clinical characteristics were recorded. The propensity score matching method was used to eliminate the difference between group with dihydropyridine calcium channel blocker and group without dihydropyridine calcium channel blocker. The primary outcome was in-hospital mortality. We used univariate and multivariate regression analyses for both patients with or without propensity score matching to assess the effect of these variables on mortality. In the subset of 186 patients with propensity score matching, in-hospital mortality was 53.2%. Inpatient mortality was significantly higher in patients treated with dihydropyridine calcium channel blocker than in those not treated with dihydropyridine calcium channel blocker of patients without propensity score matching (65.4% vs 40.4%; p < 0.01). Multivariate analysis for patients without propensity score matching showed that dihydropyridine calcium channel blocker (hazard ratio, 1.954; 95% CI, 1.415-2.699), lactate dehydrogenase greater than or equal to 600 U/L (hazard ratio, 3.809; 95% CI, 2.106-4.531), and lactate greater than or equal to 2 mmol/L (hazard ratio, 1.454; 95% CI, 1.041-2.029) were independently associated with in-hospital mortality. Based on univariate analysis for patients with propensity score matching, dihydropyridine calcium channel blocker (hazard ratio, 2.021; 95% CI, 1.333-3.064), lactate dehydrogenase greater than or equal to 600 U/L (hazard ratio, 4.379; 95% CI, 2.642-7.257), and lactate greater than or equal to 2 mmol/L (hazard ratio, 2.461; 95% CI, 1.534-3.951) were independently associated with in-hospital mortality. In contrast, patients not treated with dihydropyridine calcium channel blocker had a significant survival advantage over those treated with dihydropyridine calcium channel blocker in both patients without or with propensity score matching (p < 0.001; p = 0.001 by Kaplan-Meier analysis).

CONCLUSIONS

Dihydropyridine calcium channel blocker, lactate dehydrogenase greater than or equal to 600 U/L, and lactate greater than or equal to 2 mmol/L at admission were independent risk factors for patients with hypertension and moderate-severe pulmonary acute respiratory distress syndrome.

Effect of the Notch4/Dll4 signaling pathway in early gestational intrauterine infection on lung development

Intrauterine infection is an important risk factor for bronchopulmonary dysplasia (BPD). BPD is characterized by arrested lung alveolarization and impaired pulmonary vascularization. The Notch4 signaling pathway is a key regulator of vascular remodeling and angiogenesis. Therefore, the presents study investigated the expression of Notch4, delta-like canonical Notch ligand 4 (Dll4) and related factors in an in vivo rat model and in rat pulmonary microvascular endothelial cells (PMVECs) in vitro, to study the mechanisms by which intrauterine infection affects rat lung development. A rat model of intrauterine infection was established by endocervical inoculation with Escherichia scoli on embryonic day 15. The date of birth was counted as postnatal day 0 (P0). Then, the lung tissues were collected from pups at days P3-P14. The expression of Notch4, Dll4 and related factors was measured by reverse transcription-quantitative PCR and western blotting. In addition, the γ-secretase inhibitor DAPT was used to examine the effect of Notch4 signaling on PMVECs. Intrauterine E. coli infection impaired normal lung development, as indicated by decreased microvessel density, fewer alveoli, fewer secondary septa, and larger alveoli compared with the control group. Furthermore, Notch4, Dll4 and NF-κB levels were significantly increased in the E. coli-infected group at P3 compared with the control group. Similarly, the mRNA expression levels of fetal liver kinase 1 (Flk-1, a VEGF receptor) were significantly increased in the E. coli-infected group at P3 and P7. In PMVECs, the inhibition of Notch4 signaling contributed to decreases in lipopolysaccharide (LPS)-induced expression of VEGF and its receptors. Furthermore, the inhibition of Notch4/Dll4 signaling accelerated cell proliferation and decreased the apoptosis rate of LPS-induced PMVECs. LPS-induced NF-κB expression in PMVECs was also attenuated by the Notch4/Dll4 inhibitor. In conclusion, intrauterine E. coli infection impaired normal lung development, possibly through Notch4/Dll4 signaling and effects on VEGF and its receptors.

BK Channels Regulate LPS-induced CCL-2 Release from Human Pulmonary Endothelial Cells

We recently established a role for the stretch-activated two-pore-domain K+ (K2P) channel TREK-1 (K2P2.1) in inflammatory cytokine secretion using models of hyperoxia-, mechanical stretch-, and TNF-α-induced acute lung injury. We have now discovered the expression of large conductance, Ca2+-activated K+ (BK) channels in human pulmonary microvascular endothelial cells and primary human alveolar epithelial cells using semiquantitative real-time PCR, IP and Western blot, and investigated their role in inflammatory cytokine secretion using an LPS-induced acute lung injury model. As expected, LPS induced IL-6 and CCL-2 secretion from pulmonary endothelial and epithelial cells. BK activation with NS1619 decreased LPS-induced CCL-2 but not IL-6 secretion from endothelial cells and had no effect on epithelial cells, although fluorometric assays revealed that BK activation hyperpolarized the plasma membrane potential (Em) of both cell types. Interestingly, BK inhibition (Paxilline) did not alter cytokine secretion or the Em in either cell type. Furthermore, LPS treatment by itself did not affect the Em or intracellular Ca2+ concentrations. Therefore, we propose BK channel activation as a novel targeted approach to counteract LPS-induced CCL-2 secretion from endothelial cells. This protective effect appears to occur via Em hyperpolarization but independent of intracellular Ca2+ concentrations.

The protective effects of C16 peptide and angiopoietin-1 compound in lipopolysaccharide-induced acute respiratory distress syndrome

C16 peptide and angiopoietin-1 (Ang-1) have been found to have anti-inflammatory activity in various inflammation-related diseases. However, their combined role in acute respiratory distress syndrome (ARDS) has not been investigated yet. The objective of this study was to investigate the effects of C16 peptide and Ang-1 in combination with lipopolysaccharide (LPS)-induced inflammatory insult in vitro and in vivo. Human pulmonary microvascular endothelial cells and human pulmonary alveolar epithelial cells were used as cell culture systems, and an ARDS rodent model was used for in vivo studies. Our results demonstrated that C16 and Ang-1 in combination significantly suppressed inflammatory cell transmigration by 33% in comparison with the vehicle alone, and decreased the lung tissue wet-to-dry lung weight ratio to a maximum of 1.53, compared to 3.55 in the vehicle group in ARDS rats. Moreover, C  +  A treatment reduced the histology injury score to 60% of the vehicle control, enhanced arterial oxygen saturation (SO₂), decreased arterial carbon dioxide partial pressure (PCO₂), and increased oxygen partial pressure (PO₂) in ARDS rats, while also improving the survival rate from 47% (7/15) to 80% (12/15) and diminishing fibrosis, necrosis, and apoptosis in lung tissue. Furthermore, when C  +  A therapy was administered 4 h following LPS injection, the treatment showed significant alleviating effects on pulmonary inflammatory cell infiltration 24 h postinsult. In conclusion, our in vitro and in vivo studies show that C16 and Ang-1 exert protective effects against LPS-induced inflammatory insult. C16 and Ang-1 hold promise as a novel agent against LPS-induced ARDS. Further studies are needed to determine the potential for C16 and Ang-1 in combination in treating inflammatory lung diseases.

Endothelial Cells Exhibit Two Waves of P-selectin Surface Aggregation Under Endotoxic and Oxidative Conditions

Sepsis is a clinical syndrome characterized by the presence of circulating microbial endotoxins and oxidative stress. Endotoxin and oxidative stress activate endothelial cells via a convergent signaling pathway (TLR4/MyD88/PI3 K/PLCɣ/NF-B) that stimulates both the transcription of SELP gene (which encodes for human P-selectin) and the release of P-selectin from Weibel-Palade bodies (WPBs). However, time course pattern of P-selectin surface aggregation has not been established in endothelial cells under 24 h of endotoxic or oxidative stress. Our study shows that P-selectin has at least two waves of aggregation at the cell surface: one 10 min and the other 12 h after endotoxic or oxidative stress. The first wave depends exclusively on WPB delivery to the cell membrane, while the second depends on P-selectin translation machinery, ER-Golgi sorting, and WPB surface delivery. Understanding adhesion molecule dynamics in endothelial cells could provide further molecular insights to develop diagnostic or therapeutic tools to aid in the management of sepsis.

Short-Term versus Long-Term Culture of A549 Cells for Evaluating the Effects of Lipopolysaccharide on Oxidative Stress, Surfactant Proteins and Cathelicidin LL-37

Alveolar epithelial type II (ATII) cells and their proper function are essential for maintaining lung integrity and homeostasis. However, they can be damaged by lipopolysaccharide (LPS) during Gram-negative bacterial infection. Thus, this study evaluated and compared the effects of LPS on short and long-term cultures of A549 cells by determining the cell viability, levels of oxidative stress and antimicrobial peptide cathelicidin LL-37 and changes in the expression of surfactant proteins (SPs). Moreover, we compared A549 cell response to LPS in the presence of different serum concentrations. Additionally, the effect of N-acetylcysteine (NAC) on LPS-induced oxidative stress as a possible treatment was determined. Our results indicate that A549 cells are relatively resistant to LPS and able to maintain integrity even at high LPS concentrations. Their response to endotoxin is partially dependent on serum concentration. NAC failed to lower LPS-induced oxidative stress in A549 cells. Finally, LPS modulates SP gene expression in A549 cells in a time dependent manner and differences between short and long-term cultures were present. Our results support the idea that long-term cultivation of A549 cells could promote a more ATII-like phenotype and thus could be a more suitable model for ATII cells, especially for in vitro studies dealing with surfactant production.

Correlations of IL-17 and NF-κB gene polymorphisms with susceptibility and prognosis in acute respiratory distress syndrome in a chinese population

The present study was performed to investigate the association between interleukin-17 (IL-17) and nuclear factor κB (NF-κB) gene polymorphisms and the risk and prognosis of acute respiratory distress syndrome (ARDS) in a Chinese population. A total of 210 Chinese patients with ARDS were selected as the study group, 210 individuals who were identified as at-risk patients but did not meet criteria for ARDS were recruited as the control group. Three single nucleotide polymorphisms (SNPs) of IL-17, including rs763780 (A>G), rs2275913 (G>A), rs8193036 (C>T) and NF-κB1 gene rs3774934 (G>A) loci were examined by Sanger sequencing technique in the peripheral blood of all subjects. Patients were followed for 30-day survival. The IL-17 rs763780 and NF-κB1 rs3774934 SNPs had no impact on ARDS risk and prognosis of ARDS (P>0.05). Compared with individuals carrying the wild-type GG genotype of rs2275913 at IL-17, the AA-homozygous and GA- heterozygous individuals were protected from the development of ARDS. Consistently, a decreased 30-day mortality risk was found among A-allele carriers of rs2275913 at IL-17 (p<0.05). For IL-17 rs8193036 SNP, the homozygote TT genotype and heterozygote CT genotypes were associated with increased ARDS susceptibility and 30-day mortality risk (P<0.05). Besides, decreased IL-17 levels were found in A-allele carriers of IL-17 rs2275913, whereas individuals carrying T-allele of IL-17 rs8193036 were found to have significantly increased levels of IL-17 (P<0.05). Our results suggested that two functional polymorphisms of IL-17, rs2275913 and rs8193036 were associated with ARDS risk and prognosis, indicating that the two genetic variants might act as possible markers for the prediction of ARDS risk and development.

Polydimethylsiloxane SlipChip for mammalian cell culture applications

A polydimethylsiloxane (PDMS) SlipChip for in vitro mammalian cell culture applications, including multiple-treatment assays, cell co-culture, and cytokine detection assays.