Bei Mu Gua Lou San facilitates mucus expectoration by increasing surface area and hydration levels of airway mucus in an air-liquid-interface cell culture model of the respiratory epithelium

BACKGROUND

Bei Mu Gua Lou San (BMGLS) is an ancient formulation known for its moisturizing and expectorant properties, but the underlying mechanisms remain unknown. We investigated concentration-dependent effects of BMGLS on its rehydrating and mucus-modulating properties using an air-liquid-interface (ALI) cell culture model of the Calu-3 human bronchial epithelial cell line and primary normal human bronchial epithelial cells (NHBE), and specifically focused on quantity and composition of the two major mucosal proteins MUC5AC and MUC5B.

METHODS

ALI cultures were treated with BMGLS at different concentrations over three weeks and evaluated by means of histology, immunostaining and electron microscopy. MUC5AC and MUC5B mRNA levels were assessed and quantified on protein level using an automated image-based approach. Additionally, expression levels of the major mucus-stimulating enzyme 15-lipoxygenase (ALOX15) were evaluated.

RESULTS

BMGLS induced concentration-dependent morphological changes in NHBE but not Calu-3 ALI cultures that resulted in increased surface area via the formation of herein termed intra-epithelial structures (IES). While cellular rates of proliferation, apoptosis or degeneration remained unaffected, BMGLS caused swelling of mucosal granules, increased the area of secreted mucus, decreased muco-glycoprotein density, and dispensed MUC5AC. Additionally, BMGLS reduced expression levels of MUC5AC, MUC5B and the mucus-stimulating enzyme 15-lipoxygenase (ALOX15).

CONCLUSIONS

Our studies suggest that BMGLS rehydrates airway mucus while stimulating mucus secretion by increasing surface areas and regulating goblet cell differentiation through modulating major mucus-stimulating pathways.

Alox15/15-HpETE Aggravates Myocardial Ischemia-Reperfusion Injury by Promoting Cardiomyocyte Ferroptosis

BACKGROUND

Myocardial ischemia-reperfusion (I/R) injury causes cardiac dysfunction to myocardial cell loss and fibrosis. Prevention of cell death is important to protect cardiac function after I/R injury. The process of reperfusion can lead to multiple types of cardiomyocyte death, including necrosis, apoptosis, autophagy, and ferroptosis. However, the time point at which the various modes of cell death occur after reperfusion injury and the mechanisms underlying ferroptosis regulation in cardiomyocytes are still unclear.

METHODS

Using a left anterior descending coronary artery ligation mouse model, we sought to investigate the time point at which the various modes of cell death occur after reperfusion injury. To discover the key molecules involved in cardiomyocyte ferroptosis, we performed a metabolomics study. Loss/gain-of-function approaches were used to understand the role of 15-lipoxygenase (Alox15) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (Pgc1α) in myocardial I/R injury.

RESULTS

We found that apoptosis and necrosis occurred in the early phase of I/R injury, and that ferroptosis was the predominant form of cell death during the prolonged reperfusion. Metabolomic profiling of eicosanoids revealed that Alox15 metabolites accumulated in ferroptotic cardiomyocytes. We demonstrated that Alox15 expression was specifically increased in the injured area of the left ventricle below the suture and colocalized with cardiomyocytes. Furthermore, myocardial-specific knockout of Alox15 in mice alleviated I/R injury and restored cardiac function. 15-Hydroperoxyeicosatetraenoic acid (15-HpETE), an intermediate metabolite derived from arachidonic acid by Alox15, was identified as a trigger for cardiomyocyte ferroptosis. We explored the mechanism underlying its effects and found that 15-HpETE promoted the binding of Pgc1α to the ubiquitin ligase ring finger protein 34, leading to its ubiquitin-dependent degradation. Consequently, attenuated mitochondrial biogenesis and abnormal mitochondrial morphology were observed. ML351, a specific inhibitor of Alox15, increased the protein level of Pgc1α, inhibited cardiomyocyte ferroptosis, protected the injured myocardium, and caused cardiac function recovery.

CONCLUSIONS

Together, our results established that Alox15/15-HpETE-mediated cardiomyocyte ferroptosis plays an important role in prolonged I/R injury.

[Effects of 12/15-lipoxygenase antisense oligonucleotide on peroxisome proliferator-activated receptor γ translocation in primarily cultured cortical neurons after oxygen-glucose deprivation]

OBJECTIVE

To explore the effects of 12/15-lipoxygenase antisense oligonucleotide (asON-12/15-LOX) on OGD (oxygen-glucose deprivation)-induced PPARγ (peroxisome proliferator-activated receptor γ) expression and nuclear translocation in primarily cultured cortical neurons.

METHODS

After a 48-h pre-treatment of 12/15-LOX antisense oligonucleotide (asON), primarily cultured cortical neurons underwent 3-hour OGD followed by a 24-hour reperfusion.Immunofluorescent staining and Western blot were used to evaluate the expressions of 12/15-LOX and PPARγ as well as the nuclear translocation of PPARγ.

RESULTS

Compared with the control group, the expressions of 12/15-LOX and PPARγ whole protein were enhanced in OGD group (t = -3.72 and -6.79, P = 0.03 and 0.04). And an increase of PPARγ in nucleus (t = -4.67, P = 0.02) could be noted with a simultaneous reduction in cytosol (t = 3.40, P = 0.04) after OGD, indicating an induction of nuclear translocation by OGD. Compared with OGD group, a pre-treatment of asON-12/15-LOX dramatically attenuated OGD-induced increase in 12/15-LOX whole protein expression (t = 5.03, P = 0.02). Compared with OGD group, a pre-treatment of asON-12/15-LOX greatly reduced OGD-induced increase in PPARγ total protein expression (t = 2.83, P = 0.04) and nuclear translocation (t = 7.05, P = 0.01 for nuclear protein; t = -5.47, P = 0.01 for cytosol protein). It indicated a possible link between 12/15-LOX and PPARγ.

CONCLUSION

12/15-LOX antisense oligonucleotide suppresses the expression and nuclear translocation of PPARγ in primarily cultured cortical neurons after OGD.

In vitro screening of Crataegus succulenta extracts for free radical scavenging and 15-lipoxygenase inhibitory activities

Crataegus succulenta Schrad. ex Link is widely spread in North America. A literature survey revealed no studies on the chemical composition and biological effects of this species.

AIM

The aim of the present study was to investigate the phenolic content, free radical scavenging and 15-lipoxygenase inhibitory effects of Crataegus succulenta leaf and flower extracts.

MATERIAL AND METHODS

Total phenolic, flavonoid and proanthocyanidin contents were quantified by spectrophotometric methods. Both extracts were evaluated for their ability to scavenge DPPH, superoxide anion and hydroxyl radicals and to inhibit 15-lipoxygenase activity.

RESULTS

There were noticed no striking differences in the total phenolic, flavonoid and proanthocyanidin contents between leaf and flower extracts. Both extracts showed similar 15-lipoxygenase inhibitory effects. Flower extract scavenged more effectively DPPH and superoxide radicals while leave extract was more active against hydroxyl radical. In superoxide anion radical scavenging assay, both extracts were more active than (+)-catechin. In hydroxyl radical scavenging and 15-lipoxygenase inhibition assays, the extracts were only 4-5 times less active than (+)-catechin.

CONCLUSIONS

The high antioxidant potential of Crataegus succulenta extracts suggest a possible use as ingredients in functional foods for the prevention of oxidative stress-related diseases.

Modification of HDL3 by mild oxidative stress increases ATP-binding cassette transporter 1-mediated cholesterol efflux

OBJECTIVE

Elevated levels of high-density lipoprotein (HDL) cholesterol are inversely related to the risk of cardiovascular disease. The anti-atherosclerotic function of HDL is mainly ascribed to its role in reverse cholesterol transport, and requires the integrity of HDL structure. Experimental evidence suggests that the ability of HDL to promote removal of excess cholesterol from peripheral cells is impaired upon oxidation. On the other hand, tyrosylation of HDL enhances its protective function, suggesting that not all forms of modified lipoprotein may be atherogenic. In the present study we investigated the effect of a mild oxidation of HDL(3) on its function as cholesterol acceptor.

METHODS AND RESULTS

A mild oxidative stress (induced by 15 min exposure of HDL(3) to 1 microM Cu(++) or to 15-lipoxygenase) caused the formation of pre-beta-migrating particles. Compared to native lipoprotein, mildly modified HDL(3) induced a significant ATP-binding cassette transporter 1 (ABCA1)-mediated increase of cholesterol and phospholipids efflux from J774 macrophages. This effect was abolished by an inhibitor of ABCA1-mediated lipid efflux (glyburide) and was absent in Tangier fibroblasts.

CONCLUSIONS

A mild oxidative modification of HDL(3) may improve its function as cholesterol acceptor, increasing ABCA1-mediated lipid efflux from macrophages, a process that may reduce foam cell formation.

15-Lipoxygenase-1 mediates nonsteroidal anti-inflammatory drug-induced apoptosis independently of cyclooxygenase-2 in colon cancer cells

We previously found (I. Shureiqi et al., Carcinogenesis (Lond.), 20: 1985-1995, 1999; I. Shureiqi et al, J. Natl. Cancer Inst., 92: 1136-1142, 2000) that (a) 15-lipoxygenase-1 (15-LOX-1) protein and its product 13-S-hydroxyoctadecadienoic acid (13-S-HODE) are decreased; and (b) nonsteroidal anti-inflammatory drug (NSAID)-induced 15-LOX-1 expression is critical to NSAID-induced apoptosis in colorectal cancer cells expressing cyclooxygenase-2 (COX-2). We used the NSAIDs sulindac sulfone (COX-2-independent) and NS-398 (a COX-2 inhibitor) to assess NSAID upregulation of 15-LOX-1 in relation to COX-2 inhibition during NSAID-induced apoptosis in the DLD-1 (COX-2-negative) colon cancer cell line. We found that: (a) NSAIDs up-regulated 15-LOX-1, which preceded apoptosis; and (b) 15-LOX-1 inhibition blocked NSAID-induced apoptosis, which was restored by 13-S-HODE but not by its parent, linoleic acid. NSAIDs can induce apoptosis in colon cancer cells via up-regulation of 15-LOX-1 in the absence of COX-2.

Effects of soybean lipoxygenase on Na+/K+-ATPase activity in vitro

Oxidized metabolites of polyunsaturated fatty acids produced by lipoxygenase are among the endogenous regulators of Na+/K+-ATPase. The direct effect of lipoxygenase on Na+/K+-ATPase activity was assessed in vitro using soybean lipoxygenase. Treatment of 4.2 microg/mL Na+/K+-ATPase (from dog kidneys) with 4.2 microg/mL of soybean lipoxygenase caused 20+/-2% inhibition of ATPase activity. A 10-fold increase in lipoxygenase concentration (41.6 microg/mL) led to 30+/-0.3% inhibition. In the presence of 12 microg/mL phenidone (a lipoxygenase inhibitor) and 15.4 microg/mL glutathione (a tripeptide containing a cysteine residue) inhibition of Na+/K+-ATPase activity was blocked and an increase in ATPase activity was observed. The presence of lipoxygenase enhanced the inhibition of Na+/K+-ATPase activity caused by 20 ng/mL ouabain (31+/-2 vs. 19+/-2) but had little or no effect with higher concentrations of ouabain. These findings suggest that lipoxygenase may regulate Na+/K+-ATPase by acting directly on the enzyme.

Lipoxygenase treatment render low-density lipoprotein susceptible to Cu2+-catalysed oxidation

Oxidative modification of low-density lipoprotein (LDL) has been implicated in foam-cell formation at all stages of atherosclerosis. Since transition metals and mammalian 15-lipoxygenases are capable of oxidizing LDL to its atherogenic form, a concerted action of these two catalysts in atherogenesis has been suggested. Cu2+-catalysed LDL oxidation is characterized by a kinetic lag period in which the lipophilic antioxidants are decomposed and by a complex mixture of unspecific oxidation products. We investigated the kinetics of the 15-lipoxygenase-catalysed oxygenation of LDL and found that the enzyme is capable of oxidizing LDL in the presence of the endogenous lipophilic antioxidants. In contrast with the Cu2+-catalysed reaction, no kinetic lag phase was detected. The pattern of products formed during short-term incubations was highly specific, with cholesterol-esterified (13S)-hydroperoxy-(9Z,11E)-octadecadinoic acid being the major product. However, after long-term incubations the product pattern was less specific. Preincubation with 15-lipoxygenase rendered human LDL more susceptible to Cu2+-catalysed oxidation as indicated by a dramatic shortening of the lag period. Addition of Cu2+ to lipoxygenase-treated LDL led to a steep decline in its antioxidant content and to a greatly reduced lag period. Interestingly, if normalized to a comparable hydroperoxide content, autoxidation and addition of exogenous hydroperoxy fatty acids both failed to overcome the lag period. The local peroxide concentrations in various LDL subcompartments will be discussed as a possible reason for this unexpected behaviour.

Oxygenation of biomembranes by mammalian lipoxygenases: the role of ubiquinone

15-Lipoxygenase is implicated in the selective breakdown of mitochondria during red cell maturation by virtue of its capability of directly oxygenating phospholipids. To address the reason of the selectivity for mitochondria, we studied the reaction of pure rabbit 15-lipoxygenase with beef heart submitochondrial particles in vitro. This reaction is characterised by a loss of polyenoic fatty acids, the formation of phospholipid-bound hydroperoxy- and keto-polyenoic fatty acids, and oxidative modification of membrane proteins. The total oxygen uptake exceeds the formation of oxygenated polyenoic fatty acids several times. The excessive oxygen uptake was not inhibited by 3,5-di-tert-butyl-4-hydroxytoluene or by respiratory inhibitors, but was partly suppressed by superoxide dismutase plus catalase, salicylate, or mannitol. Pentane-extraction of the submitochondrial particles abolished the excessive oxygen uptake, whereas reconstitution with ubiquinone- 50 restored it. A marked excessive oxygen uptake did not occur during the analogous reaction with erythrocyte ghosts. It is proposed that ubiquinone-50 triggers the formation of hydroxyl radicals from 15-lipoxygenase-derived hydroperoxy-lipids via a Fenton-type reaction driven by ubisemiquinone radicals. A new prooxidative function of ubiquinone in the biologically programmed degradation of mitochondria in certain types of cells is proposed.

Role of the lipoxygenase pathway in angiotensin II-induced vascular smooth muscle cell hypertrophy

The 12-lipoxygenase pathway is a key mediator of angiotensin II (Ang II)-induced effects in the adrenal cortex. We also recently demonstrated that Ang II increases 12- and 15-lipoxygenase product levels in vascular smooth muscle cells. However, the relation between lipoxygenase activation and Ang II-induced vascular smooth muscle cell hypertrophy is not known. We studied the effects of Ang II and 12-lipoxygenase products on both total cell protein content and the levels of the matrix protein fibronectin in quiescent porcine aortic smooth muscle cells. Ang II-induced increases in cellular protein content were attenuated by the specific 12-lipoxygenase inhibitor baicalein; in contrast, the cyclooxygenase inhibitor ibuprofen had no effect. Direct addition of the 12-lipoxygenase product 12-S-hydroxyeicosatetraenoic acid increased total cell protein content. We have recently shown that porcine vascular smooth muscle cell growth is potentiated in high glucose (25 mmol/L) culture conditions. We observed that both Ang II and 12-S-hydroxyeicosatetraenoic acid induced a greater increase in protein content in cells cultured for two passages in high glucose. Furthermore, Ang II and 12-S-hydroxyeicosatetraenoic acid also markedly increased fibronectin levels in cells cultured in high glucose. These results suggest that 12-lipoxygenase activation plays a key role in Ang II-induced vascular smooth muscle cell hypertrophy. Furthermore, both Ang II and lipoxygenase effects are enhanced in cells cultured under hyperglycemic conditions.