The cysteinyl leukotriene receptor 1 (CysLT1R) antagonist montelukast suppresses matrix metalloproteinase-13 expression induced by lipopolysaccharide

Inhibition of sepsis-induced pancreatic injury by leukotriene receptor antagonism via modulation of oxidative injury, and downregulation of inflammatory markers in experimental rats

The purpose of this study is to investigate the effect of montelukast on lipopolysaccharide (LPS)-induced pancreatitis. Adult male Wistar rats were divided into 5 groups: normal control, control montelukast, LPS group, and two LPS + montelukast-treated groups. Acute pancreatitis (AP) was induced by a single dose of LPS (6 mg/kg, i.p.), while montelukast was given in two different doses (10 and 20 mg/kg/day) for 3 consecutive days prior to the injection of LPS. AP was demonstrated by significant increases in serum levels of lactate dehydrogenase (LDH) and pancreatic enzymes lipase and amylase. Proinflammatory response activation was evident by elevated serum levels of nitric oxide (NO) and increased pancreatic concentrations of tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1β), and intercellular adhesion molecule-1 (ICAM-1). The activity of myeloperoxidase (MPO), a neutrophil infiltration marker, has also been increased. Oxidative stress was confirmed by significant increases in the concentrations of lipid peroxides measured as thiobarbituric acid reactive substances (TBARS) and decreases in the concentrations of reduced glutathione (GSH) in the pancreatic tissues of animals treated with LPS. Histological examination confirmed the biochemical alterations. Montelukast treatment reversed all these biochemical indices and histopathological changes that LPS induced. Montelukast reduced the increase in serum levels of lipase, amylase, LDH, total nitrite/nitrate, TNF-α, IL-1β, and ICAM-1. MPO activities and TBARS concentrations were also suppressed while GSH content was increased in pancreatic tissues. These results show that montelukast may be a beneficial pharmacological agent in protection against LPS-induced oxidative pancreatic injury by inhibiting neutrophil infiltration, counteracting oxidative stress, and suppressing inflammatory mediators.

Leukotriene receptor antagonist reduces inflammation and alveolar bone loss in a rat model of experimental periodontitis

BACKGROUND

Leukotrienes (LTs) participate in the process of tissue damage in periodontal disease by leukocyte chemotaxis and osteoclastic activation. The activation of Cysteinyl-LT receptor is associated with increased expression of proinflammatory molecules and osteoclastogenesis. However, its implications on periodontal disease progression have not been studied. The present study evaluated the effect of the cysteinyl-LT receptor antagonist (montelukast [MT]) on ligature-induced experimental periodontitis (EP) in rats.

METHODS

Adult male Wistar rats were subjected to bilateral ligature-induced periodontitis and orally treated with MT (at doses of 10 or 30 mg/kg/d, MT10, and MT30, respectively). Sham animals had the ligatures immediately removed and received placebo treatment. Sets of animals were euthanized 7, 14, or 21 days after ligature placement and the mandibles were removed for macroscopic evaluation of alveolar bone loss (ABL). In addition, histological analysis of periodontal tissues, myeloperoxidase (MPO) activity of gingival tissues, and periodontal tissue expression of collagen type I, RUNX2, RANK, RANKL, OPG, BLT1, Cys-LTR1, LTA4H, and LTC4S were also analyzed.

RESULTS

MT significantly reduced ABL at 14 (MT10 and MT30) and 21 days (MT10) (P < 0.05), gingival MPO at 7 (MT10) and 14 days (MT30) (P < 0.05), LTA4H, BLT1 and LTC4S gene expression on day 14 day (MT30, P < 0.05) and increased RUNX2 expression on day 14 (MT30, P < 0.05).

CONCLUSION

Systemic therapy with MT decreases periodontal inflammation and ABL in ligature-induced periodontitis in rats.

Targeting matrix metalloproteinase-13 in bronchial epithelial repair

BACKGROUND

Viral infection of the bronchial epithelium disrupts the barrier properties of the epithelium in healthy individuals and those with lung disease. Repair of the bronchial epithelium is dependent of the formation of a provisional fibrin matrix and migration of epithelial cells to cover denuded areas, followed by proliferation and differentiation.

OBJECTIVE

The objective was to test the hypothesis that poly I:C, a model of viral infection, limits epithelial repair through the stimulated release of matrix metalloproteinase-13 (MMP-13).

METHODS

Confluent layers of cultured normal human primary bronchial epithelial cells (NHBE) and SV-40 virus-transformed 16HBE14o- bronchial epithelial cells were mechanically wounded, and video microscopy used to measure the rate of wound closure over 2 hours, in the absence and presence of poly I:C (1-20 μg/mL). MMP-13, tissue factor and endothelin release were measured by ELISA. The effect of inhibitors of MMP-13 activity and expression and a nonspecific endothelin receptor antagonist, bosentan, on the rate of epithelial repair was investigated.

RESULTS

Poly I:C limited the rate of epithelial repair, and NHBE were significantly more sensitive to poly I:C effects than 16HBE14o- cells. NHBE, but not 16HBE14o-, released MMP-13 in response to poly I:C. Inhibitors of MMP-13 activity (WAY 170523) and expression (dimethyl fumarate) significantly enhanced the rate of repair. Bosentan enhanced the rate of bronchial epithelial repair by a mechanism that was independent of MMP-13.

CONCLUSIONS AND CLINICAL RELEVANCE

Bronchial epithelial repair is limited by endothelin and by MMP-13, a protease that degrades coagulation factors, such as fibrinogen, and matrix proteins essential for epithelial repair. Further studies with primary cells from patients are needed to confirm whether repurposing bosentan and inhibitors of MMP-13 expression or activity, for inhalation may be a useful therapeutic strategy in diseases where repeated cycles of epithelial injury and repair occur, such as asthma and COPD.

Cysteinyl leukotriene receptor 1 regulates glucose-stimulated insulin secretion (GSIS)

Insulin resistance is an important pathological hallmark of type 2 diabetes mellitus. Glucose-stimulated insulin secretion (GSIS) plays a key role in maintaining blood glucose levels within normal range. Impaired GSIS has been associated with type 2 diabetes, however, the underlying molecular mechanisms remain largely unknown. Cysteinyl leukotriene receptor 1 (cysLT1R) is an important G protein-coupled receptor mediating the biological functions of cysteinyl leukotrienes (cys-LTs). Little is known about the effects of cysLT1R in insulin secretion and pathogenesis of T2DM. In the present study, we aimed to define the physiological functions of cysLT1R in GSIS in MIN6 β-cells. Using reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis, we found that cysLT1R was expressed in pancreatic MIN6 β-cells. We also reported that glucose increased the expression of cysLT1R in MIN6 cells. Additionally, the cysLT1R antagonist montelukast promoted GSIS in a dose dependent manner, however, the cysLT1R agonist LD4 inhibited GSIS, suggesting an antagonistic effect of cysLT1R on GSIS. Silencing of cysLT1R by transfection with cysLT1R siRNA enhanced GSIS while overexpression of cysLT1R reduced GSIS in pancreatic MIN6 β-cells. Mechanistically, we found that the Arf6/Cdc42/Rac1 pathway was involved in this process. Collectively, our findings highlight the essential role of cysLT1R in suppressing pancreatic insulin secretion, and potentially provided a new insight into understanding the mechanical regulation of glucose homeostasis.