LPS-induced neutrophilic inflammation and Bcl-2 expression in metaplastic mucous cells

Neuroprotective Effect of Bcl-2 on Lipopolysaccharide-Induced Neuroinflammation in Cortical Neural Stem Cells

Neuroinflammation is involved in the pathogenesis of neurodegenerative diseases due to increased levels of pro-inflammatory cytokines in the central nervous system (CNS). Chronic neuroinflammation induced by neurotoxic molecules accelerates neuronal damage. B-cell lymphoma 2 (Bcl-2) is generally accepted to be an important anti-apoptotic factor. However, the role of Bcl-2 in neuroprotection against neuroinflammation remains to be determined. The purpose of this study was to investigate the neuroprotective effect of Bcl-2 on lipopolysaccharide (LPS)-induced neuroinflammation in cortical neural stem cells (NSCs). LPS decreased mRNA and protein levels of Tuj-1, a neuron marker, and also suppressed neurite outgrowth, indicating that LPS results in inhibition of neuronal differentiation of NSCs. Furthermore, LPS treatment inhibited Bcl-2 expression during neuronal differentiation; inhibition of neuronal differentiation by LPS was rescued by Bcl-2 overexpression. LPS-induced pro-inflammatory cytokines, including interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), were decreased by Bcl-2 overexpression. Conversely, Bcl-2 siRNA increased the LPS-induced levels of IL-6 and TNF-α, and decreased neuronal differentiation of NSCs, raising the possibility that Bcl-2 mediates neuronal differentiation by inhibiting the LPS-induced inflammatory response in NSC. These results suggest that Bcl-2 has a neuroprotective effect by inhibiting the LPS-induced inflammatory response in NSCs.

Bezafibrate Exerts Neuroprotective Effects in a Rat Model of Sporadic Alzheimer’s Disease

Bezafibrate, a pan-peroxisome proliferator-activated receptor (PPAR) agonist, reportedly attenuated tau pathology in a transgenic mouse model of primary tauopathy. Since tau pathology is a neuropathological hallmark of Alzheimer’s disease (AD), bezafibrate may be a potential drug for the treatment of AD. However, no study has investigated its effects in AD models. Thus, we aimed to evaluate whether bezafibrate has neuroprotective effects in a sporadic AD model induced by streptozotocin (STZ) intracerebroventricular (ICV) injection. Rats were administered STZ-ICV (3 mg/kg) followed by bezafibrate (50 mg/kg/day, intraperitoneal) for 4 weeks. Behavior tests and positron emission tomography (PET) were performed to evaluate longitudinal changes in cognitive function, tau pathology, and cerebral glucose metabolism. Immunofluorescence staining was performed to assess neuronal survival and microglial accumulation. STZ-ICV administration induced significant cognitive impairment and substantial neuronal loss, tau pathology, glucose hypometabolism, and microgliosis in the cortex and hippocampus, while bezafibrate effectively attenuated these abnormalities. This study demonstrated that bezafibrate has long-lasting neuroprotective effects in a sporadic AD model. Our data indicate that the neuroprotective effects of bezafibrate might be associated with its ability to ameliorate tau pathology, brain glucose hypometabolism, and neuroinflammation. These findings suggest that bezafibrate is a potential multi-target drug candidate for the treatment of AD.

IL-13 in LPS-Induced Inflammation Causes Bcl-2 Expression to Sustain Hyperplastic Mucous cells

Exposure to lipopolysaccharides (LPS) causes extensive neutrophilic inflammation in the airways followed by mucous cell hyperplasia (MCH) that is sustained by the anti-apoptotic protein, Bcl-2. To identify inflammatory factor(s) that are responsible for Bcl-2 expression, we established an organ culture system consisting of airway epithelial tissue from the rat nasal midseptum. The highest Muc5AC and Bcl-2 expression was observed when organ cultures were treated with brochoalveolar lavage (BAL) fluid harvested from rats 10 h post LPS instillation. Further, because BAL harvested from rats depleted of polymorphonuclear cells compared to controls showed increased Bcl-2 expression, analyses of cytokine levels in lavages identified IL-13 as an inducer of Bcl-2 expression. Ectopic IL-13 treatment of differentiated airway epithelial cells increased Bcl-2 and MUC5AC expression in the basal and apical regions of the cells, respectively. When Bcl-2 was blocked using shRNA or a small molecule inhibitor, ABT-263, mucous cell numbers were reduced due to increased apoptosis that disrupted the interaction of Bcl-2 with the pro-apoptotic protein, Bik. Furthermore, intranasal instillation of ABT-263 reduced the LPS-induced MCH in bik +/+ but not bik -/- mice, suggesting that Bik mediated apoptosis in hyperplastic mucous cells. Therefore, blocking Bcl-2 function could be useful in reducing IL-13 induced mucous hypersecretion.

Tanshinone IIA therapeutically reduces LPS-induced acute lung injury by inhibiting inflammation and apoptosis in mice

AIM

To study the effects of tanshinone IIA (TIIA) on lipopolysaccharide (LPS)-induced acute lung injury in mice and the underlying mechanisms.

METHODS

Mice were injected with LPS (10 mg/kg, i.p.), then treated with TIIA (10 mg/kg, i.p.). Seven hours after LPS injection, the lungs were collected for histological study. Protein, LDH, TNF-α and IL-1β levels in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) activity in lungs were measured. Cell apoptosis and Bcl-2, caspase-3, NF-κB and HIF-1α expression in lungs were assayed.

RESULTS

LPS caused marked histological changes in lungs, accompanied by significantly increased lung W/D ratio, protein content and LDH level in BALF, and Evans blue leakage. LPS markedly increased neutrophil infiltration in lungs and inflammatory cytokines in BALF. Furthermore, LPS induced cell apoptosis in lungs, as evidenced by increased TUNEL-positive cells, decreased Bcl-2 content and increased cleaved caspase-3 content. Moreover, LPS significantly increased the expression of NF-κB and HIF-1α in lungs. Treatment of LPS-injected mice with TIIA significantly alleviated these pathological changes in lungs.

CONCLUSION

TIIA alleviates LPS-induced acute lung injury in mice by suppressing inflammatory responses and apoptosis, which is mediated via inhibition of the NF-κB and HIF-1α pathways.

Interaction of Bordetella bronchiseptica and Its Lipopolysaccharide with In Vitro Culture of Respiratory Nasal Epithelium

The nasal septa of fetal rabbits at 26 days of gestation were harvested by cesarean section of the does while under anesthesia and then exposed to Bordetella bronchiseptica or its lipopolysaccharide (LPS) for periods of 2 and 4 hours. A total of 240 explants were used. The tissues were examined using the Hematoxylin & Eosin technique. Then, semithin sections (0.5 μm) were stained with toluidine blue and examined with indirect immunoperoxidase (IPI) and lectin histochemistry. The most frequent and statistically significant findings were as follows: (1) cell death and increased goblet cell activity when exposed to bacteria and (2) cell death, cytoplasmic vacuolation and infiltration of polymorphonuclear leukocytes when exposed to LPS. The lesions induced by the bacterium were more severe than with LPS alone, except for the cytoplasmic vacuolation in epithelial cells. IPI stained the ciliated border of the epithelium with the bacterium more intensely, while LPS lectin histochemistry preferentially labeled the cytoplasm of goblet cell. These data indicate that B. bronchiseptica and its LPS may have an affinity for specific glycoproteins that would act as adhesion receptors in both locations.

Acute inflammation induces insulin-like growth factor-1 to mediate Bcl-2 and Muc5ac expression in airway epithelial cells

Generally, exposure to LPS in human airways occurs in the form of aerosols and causes an acute inflammatory response or exacerbates existing chronic inflammatory conditions by enhancing airway remodeling and associated pathologies. The present study evaluated which inflammatory mediators may be responsible for the expression of Bcl-2 and mucus cell metaplasia when mice are exposed to aerosolized LPS. At 3 days after exposure, aerosolized LPS (for 20-40 min) with the estimated lung deposited dosage of 0, 0.02, 0.2, 1.4, and 20.2 μg showed a characteristic dose-dependent increase in polymorphonuclear neutrophils. Significant increases of proinflammatory mediators, including IL-1β, TNF-α, IL-6, growth-related oncogene or keratinocyte-derived cytokine, IFN-γ-induced protein-10, monocyte chemotactic protein-1, and macrophage inflammatory protein-1α, were detected at the highest doses. In addition to increased numbers of airway epithelial cells, mucus cell numbers and mucus production were increased in a dose-dependent manner. Hyperplastic epithelial cells expressed insulin-like growth factor (IGF)-1 and, similar to previous studies, increased expression of the prosurvival protein Bcl-2 and induced expression of Muc5ac. Suppression of IGF-1 expression using retroviral shRNA blocked Bcl-2 expression in human and murine airway epithelial cells and Muc5ac in primary murine airway epithelial cells. These findings show that acute inflammation induces IGF-1 to mediate Bcl-2 and Muc5ac expression in airway epithelial cells.

Inflammation, mucous cell metaplasia, and Bcl-2 expression in response to inhaled lipopolysaccharide aerosol and effect of rolipram

Our previous studies have characterized the inflammatory response of intratracheally instilled lipopolysaccharides (LPS) in F344/N rats. To better reflect the environmentally relevant form of LPS exposure, the present study evaluated the inflammatory response of F344/N rats exposed to LPS by inhalation. Rats were exposed by nose-only inhalation to aerosolized LPS at a median particle diameter of 1 μm and a dose range from 0.08 to 480 μg. Animals were euthanized 72 h post exposure and the inflammatory cell counts and differentials, the cytokine/chemokine levels in the bronchoalveolar lavage fluid (BALF), and the changes in intraepithelial stored mucosubstances, mucous cells per mm basal lamina, and Bcl-2-positive mucous cells were quantified. We observed a dose-dependent increase reaching maximum values at the 75 μg LPS dose for the numbers of neutrophils, macrophages and lymphocytes, for the levels of IL-6, IL-1α, IL-1β, TNFα, MCP-1 and GRO-KC. In addition, mucous cell metaplasia and the percentage of Bcl-2-positive mucous cells were increased with an increasing deposited LPS dose. When rats were treated with the phosphodiesterase-4 (PDE4) inhibitor, rolipram (10mg/kg), prior to exposure to aerosolized LPS neutrophil numbers in the BAL were reduced at 8h but not at 24 or 72 h post LPS exposure. These results demonstrate that exposure to aerosolized LPS resulted in a more potent inflammatory response at lower doses and that inflammation was more uniformly distributed throughout the lung compared to inflammation caused by intratracheal LPS instillation. Therefore, this animal model will be useful for screening efficacy of anti-inflammatory drugs.

Expression of the proapoptotic protein Bax is reduced in bronchial mucous cells of asthmatic subjects

The present studies were designed to determine whether our findings in mice showing that the Bcl-2-associated protein X (Bax), which plays a role in the resolution of allergen-induced mucous cell metaplasia, can be applied to asthma in humans. Immunostaining of autopsy tissues from mild and severe asthmatic subjects showed a significant reduction in the percentage of Bax-positive mucous cells compared with those from nonasthmatic controls. To exclude the possibility that postmortem changes may have affected Bax expression, Bax mRNA levels in airway epithelial cells obtained from nonsmoking asthmatic subjects were compared with those from nonasthmatic controls. Because the number of cells obtained by bronchial brushings is limited, we developed a robust preamplification procedure of cDNA before quantitative real-time PCR to allow detection of 100 gene targets from limited sample size, even when it was prepared from partially degraded RNA. cDNA was prepared by reverse transcription from RNA isolated from bronchial epithelial cells obtained by bronchial brushings from well-characterized subjects without lung disease and from subjects with mild asthma. Quantitative analysis showed that Bax mRNA levels were significantly reduced in samples obtained from asthma patients compared with nonasthma controls. Furthermore, Bax mRNA levels were reduced when primary airway epithelial cells from 10 individuals were treated in culture with the T helper 2 cytokine IL-13. These studies show that Bax expression is reduced in airway epithelial cells of even mild asthmatic subjects and suggest that restoring Bax expression may provide a clinical approach for restoring the normal numbers of epithelial cells and reduced mucous hypersecretion in asthma.

Metalloelastase in lungs and alveolar macrophages is modulated by extracellular substance P in mice

Metalloelastase (MMP-12), mainly produced by macrophages, has been shown to play a key role in the pathogenesis of emphysema in animal models. Chronic cigarette smoke increases pulmonary MMP-12, which is closely correlated with an elevation of pulmonary substance P (SP). Because alveolar macrophages (AMs) contain the neurokinin-1 receptor (NK1R), we tested whether SP was able to trigger the upregulation of MMP-12 synthesis in AMs by acting on the NK1R. AMs isolated from bronchoalveolar lavage cells in C3H/HeN mice were cultured with control medium or SP that was coupled without or with NK1R antagonists (CP-99,994 or aprepitant) for 24 h. We found that SP significantly increased the mRNA of MMP-12 and NK1R by 11-fold and 82%, respectively, in AMs (P<0.05), and these responses were abolished by NK1R antagonists with little change in the cells' viability. Because pulmonary SP is primarily released by bronchopulmonary C-fibers (PCFs), we further asked whether destruction of PCFs would reduce SP and MMP-12. Two groups of mice were pretreated with vehicle and neonatal capsaicin (NCAP) to degenerate PCFs, respectively. Our results show that NCAP treatment significantly decreased mRNA and protein levels of SP associated with a reduction NK1R and MMP-12 in the lungs and AMs. These findings suggest that SP has a modulatory effect on pulmonary MMP-12 by acting on NK1R to trigger MMP-12 syntheses in the AMs.

Resolution of LPS-induced airway inflammation and goblet cell hyperplasia is independent of IL-18

Background

The resolution of inflammatory responses in the lung has not been described in detail and the role of specific cytokines influencing the resolution process is largely unknown.

Methods

The present study was designed to describe the resolution of inflammation from 3 h through 90 d following an acute injury by a single intratracheal instillation of F344/N rats with LPS. We documented the inflammatory cell types and cytokines found in the bronchoalveolar lavage fluid (BALF), and epithelial changes in the axial airway and investigated whether IL-18 may play a role in the resolution process by reducing its levels with anti-IL-18 antibodies.

Results

Three major stages of inflammation and resolution were observed in the BALF during the resolution. The first stage was characterized by PMNs that increased over 3 h to 1 d and decreased to background levels by d 6–8. The second stage of inflammation was characterized by macrophage influx reaching maximum numbers at d 6 and decreasing to background levels by d 40. A third stage of inflammation was observed for lymphocytes which were elevated over d 3–6. Interestingly, IL-18 and IL-9 levels in the BALF showed a cyclic pattern with peak levels at d 4, 8, and 16 while decreasing to background levels at d 1–2, 6, and 12. Depletion of IL-18 caused decreased PMN numbers at d 2, but no changes in inflammatory cell number or type at later time points.

Conclusion

These data suggest that IL-18 plays a role in enhancing the LPS-induced neutrophilic inflammation of the lung, but does not affect the resolution of inflammation.

Persistent mucus accumulation: a consequence of delayed bronchial mucous cell apoptosis in RAO-affected horses?

This study examined the contribution of delayed apoptosis of bronchial mucous cells to mucus accumulation in equine recurrent airway obstruction (RAO). In pilot studies, Bcl-2, an apoptosis inhibitor, was detected in airway mucous cells of RAO-affected horses in remission and during acute disease, when most mucus was secreted. To study whether delayed apoptosis results in an increase in the number of mucous cells during disease recovery, six RAO-affected and six control horses were fed hay for 5 days to induce inflammation and then pellets for 7 days to partially resolve RAO before euthanasia. RAO-affected horses had more airway obstruction and luminal mucus than control horses under both management systems. At the time of euthanasia, RAO-affected horses had more inflammation and Bcl-2-positive bronchial mucous cells than control animals. In horses with >10 and <10 neutrophils per microliter of bronchoalveolar lavage fluid, >50% and <10% of mucous cells stained positive for Bcl-2, respectively. No differences in mucous cell number or amount of stored mucosubstance were observed between RAO-affected and control horses, but in RAO-affected animals, the amount of stored mucosubstance decreased as the number of neutrophils in bronchoalveolar lavage fluid increased. Because the number of mucous cells was similar in both groups of horses but only mucous cells of RAO-affected horses expressed Bcl-2 during recovery from acute disease, a conclusive role for Bcl-2 in prolonging bronchial mucous cell life could not be determined. Future studies are needed to compare horses that are kept in remission for prolonged periods when all mucous cells are fully developed.

Low-level subchronic exposure to wood smoke exacerbates inflammatory responses in allergic rats

Epidemiological studies have implicated wood smoke as a risk factor for exacerbating asthma. However, comparisons of findings in animal models with those in humans are currently not possible, because detailed clinically relevant measurements of pulmonary function are not available in animal studies. Brown Norway rats were immunized with ovalbumin and exposed to either filtered air or wood smoke at 1 mg particulate matter/m(3) for 70 days and challenged with allergen during the last 4 days of exposure. Baseline values for dynamic lung compliance were lower while functional residual capacity was increased in rats exposed to wood smoke compared to rats exposed to filtered air. IFN-gamma levels were reduced and IL-4 levels increased in the bronchoalveolar lavage fluid and blood plasma, inflammatory lesions in the lungs were 21% greater, and airway mucous cells/mm basal lamina were non-significantly increased in rats exposed to wood smoke compared to controls. Collectively, these studies suggest that the pulmonary function was affected in rats by exposure to wood smoke and this decline was associated with only minor increases in inflammation of the lung. Therefore, this animal model may be useful to elucidate the mechanisms of the decline in pulmonary function caused by environmental pollutants when asthmatics are exposed to allergen.

Bcl-2 sustains increased mucous and epithelial cell numbers in metaplastic airway epithelium

Bcl-2, an inhibitor of apoptosis, is expressed in LPS-induced metaplastic goblet cells of rat airways. The present study investigated expression of Bcl-2 in airway mucous cells of persons with cystic fibrosis and tested in rats and mice whether its expression is responsible for sustaining metaplastic mucous cells. A significantly higher percentage of mucous cells expressed Bcl-2 in humans with cystic fibrosis compared with control subjects with no disease or subjects with other diseases. In LPS-instilled F344/N rats, the percentage of Bcl-2-positive mucous cells was decreased to background levels before the resolution of goblet cell metaplasia. Furthermore, intraperitoneal injection of rats with antisense oligonucleotides significantly reduced Bcl-2 expression and goblet cell metaplasia in nasal and pulmonary airway epithelia in rats. In contrast, sustained expression of Bcl-2 in transgenic mice by a metallothionein promoter caused increased LPS-induced goblet cell metaplasia over 8 days compared with wild-type mice. These studies demonstrate that Bcl-2 expression sustains goblet cell metaplasia in various species, that epithelial cell numbers are directly linked to the regulation of the numbers of goblet cells, and that downregulating Bcl-2 expression reduces goblet cell metaplasia.

Leukocyte-derived myeloperoxidase amplifies high-glucose--induced endothelial dysfunction through interaction with high-glucose--stimulated, vascular non--leukocyte-derived reactive oxygen species

Vascular non-leukocyte-derived reactive oxygen species (ROS), such as superoxide and hydrogen peroxide (H(2)O(2)), have emerged as important molecules in diabetic endothelial dysfunction. In addition, leukocyte-derived myeloperoxidase (MPO) has been implicated in vascular injury, and its injury response is H(2)O(2) dependent. It is well known that MPO can use leukocyte-derived H(2)O(2); however, it is unknown whether the vascular-bound MPO can use high-glucose-stimulated, vascular non-leukocyte-derived H(2)O(2) to induce diabetic endothelial dysfunction. In the present study, we demonstrated that MPO activity is increased in vessels from diabetic rats. In high-glucose-incubated rat aortas and in carotid arteries from rats with acute hyperglycemia, vascular-bound MPO utilized high-glucose-stimulated H(2)O(2) to amplify the ROS-induced impairment of endothelium-dependent relaxation via reduction of nitric oxide bioavailability. Hypochlorous acid (HOCL)-modified LDL, a specific biomarker for the MPO/HOCL/chlorinating species pathway, was detected in LDL- and MPO-bound vessels with high-glucose-stimulated H(2)O(2). The results suggest that vascular-bound MPO could use high-glucose-stimulated H(2)O(2) to amplify high-glucose-induced injury in the vascular wall. MPO/H(2)O(2)/HOCL/chlorinating species may represent an important pathway in diabetes complications and a new mechanism in phagocyte- and systemic infection-induced exacerbation of diabetic vascular diseases.