A Comparison of Arginase Activity in the Saliva Plasma and Peripheral Blood Mononuclear Cells(PBMC)of Pulmonary Tuberculosis Patients in Addis Ababa, Ethiopia
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Date
2011-05
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Addis Ababa University
Abstract
Background: Mycobacterium tuberculosis (MTB)is the causative organism of the chronic bacterial infection, tuberculosis (TB). TB is one of the leading causes of death due to infectious diseases worldwide. Recently it has been observed that arginase (ARG)-is no longer a mere enzyme responsible only for urea cycle but is a key enzyme that plays a great role in modulation of the immune response and thus, pathogenesis. Infection with MTB and other intracellular pathogens induces the activation of ARG and inducible nitric oxide synthase (iNOS) which competitively metabolize L-arginine as a common substrate to produce L-ornithine and nitric oxide (NO), respectively. ARG induced deprivation of Larginine is important for pathogens to limit the intracellular production and killing action of NO and T cell responses. Therefore, induction of ARG might be an important escape mechanism for the survival of MTB.
Materials and Methods: A cross-sectional study was carried out to compare the level of ARG activity in the saliva, plasma and peripheral blood mononuclear cells (PBMCs)of newly diagnosed HIV sero -negative smear positive TB patients (n=18) and healthy controls (n=8). The level of arginase activity in all type of samples was measured by enzymatic assay and a two-tailed Mann-Whitney U test was performed to assess statistical differences.
Results: There was a statistically significantly higher level of arginase activity in the PBMCs (p=0.015)and saliva (p=0.008)of TB patients than those of healthy controls. Furthermore, an increased level of arginase activity was detected in the plasma of TB patients as compared to healthy controls, however it was not statistically significant (p=0.211). A significantly higher (p=0.024)frequency of arginase expressing cells were detected in the PBMCs of TB patients as compared to healthy controls. The phenotype of these cells was identified as CD15 + neutrophile.
Conclusions and recommendation: Infection with MTB can result in an increased frequency of ARG-expressing cells as well as in increased level of arginase activity in the PBMCs, saliva and plasma of the TB patients. Therefore, the measurement of ARG activity in saliva might be used as a biomarker of TB infection.
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Arginase, TB, PBMC and saliva.