Related Experiment Videos
Effect of ammonium metavanadate on the mouse peritoneal macrophage lysosomal enzymes
1Food Science and Human Nutrition Department, University of Florida, Gainesville 32611-0163.
Abstract:
Female B6C3F1 mice were injected intraperitoneally with ammonium metavanadate (2.5 or 10 mg V/kg), ammonium chloride, or sodium phosphate buffer (0.1 M, pH 7.2) every 3 d for 6 wk. Resident peritoneal macrophage (PEM) cytolysates were prepared and assayed for intracellular enzyme activities of beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, acid phosphatase, and lysozyme, to investigate possible reasons for the depressive effect of ammonium metavanadate on the intracellular killing of Listeria monocytogenes by murine PEM. Acid phosphatase activity per 10(6) cells for the 2.5 and 10 mg V/kg groups was depressed by 22.8 and 44.7%, respectively, when compared to phosphate buffer controls. No significant effect by vanadium treatment was observed with regard to the other three enzymes. Kinetic studies (in vitro) on the effect of ammonium metavanadate (5, 10, 15, and 20 mM) on the above enzymes showed similar patterns of effect by vanadium. Lineweaver-Burk analysis of acid phosphatase indicated linear noncompetitive inhibition by vanadium with a Kj of 14.8 mM. NH4Cl and 10 mg V/kg treatments also enhanced extracellular secretion of beta-glucuronidase and lysozyme from PEM, which could be attributed to the presence of ammonium ion. The decrease in acid phosphatase activity might contribute, in part through its interference in the phosphorylation/dephosphorylation, to the diminished intracellular killing ability of PEM.
Insights
Ammonium metavanadate exposure in mice significantly reduced acid phosphatase activity in peritoneal macrophages, potentially impairing their ability to kill Listeria monocytogenes. This enzyme inhibition is linked to vanadium
Area of Science:
- Immunotoxicology
- Biochemistry
Background:
- Ammonium metavanadate exposure can impact immune cell function.
- Peritoneal macrophages (PEM) are crucial for intracellular pathogen killing.
- Acid phosphatase is an important lysosomal enzyme involved in cellular defense.
Purpose of the Study:
- To investigate the effect of ammonium metavanadate on intracellular enzyme activities in murine peritoneal macrophages (PEM).
- To determine the impact of ammonium metavanadate on the killing of Listeria monocytogenes by PEM.
- To elucidate the biochemical mechanisms underlying vanadium-induced immunomodulation.
Main Methods:
- Female B6C3F1 mice were administered ammonium metavanadate, ammonium chloride, or phosphate buffer intraperitoneally for 6 weeks.
- Resident peritoneal macrophage (PEM) cytolysates were analyzed for intracellular enzyme activities (beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, acid phosphatase, lysozyme).
- In vitro kinetic studies and Lineweaver-Burk analysis were performed to assess vanadium's inhibitory effects on acid phosphatase.
Main Results:
- Ammonium metavanadate significantly depressed acid phosphatase activity in a dose-dependent manner (22.8% at 2.5 mg V/kg, 44.7% at 10 mg V/kg).
- No significant effects were observed on beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, or lysozyme activities.
- In vitro studies confirmed noncompetitive inhibition of acid phosphatase by vanadium (Kj = 14.8 mM).
- Ammonium chloride and high-dose vanadium enhanced extracellular secretion of beta-glucuronidase and lysozyme.
Conclusions:
- Vanadium-induced decrease in acid phosphatase activity may contribute to the impaired intracellular killing of Listeria monocytogenes by murine PEM.
- Acid phosphatase inhibition by vanadium likely occurs through interference with phosphorylation/dephosphorylation processes.
- The findings highlight the immunotoxic potential of ammonium metavanadate, specifically targeting macrophage enzymatic functions.