Elevated 1- α hydroxylase activity in monocytes from patients with active tuberculosis

Area of Science:

• Endocrinology
• Immunology
• Infectious Diseases

Background:

• Hypercalcemia in uremic patients can be linked to tuberculosis infection and vitamin D metabolism.
• The kidneys are the primary site for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) production, but alternative sources are being investigated.

Purpose of the Study:

• To investigate whether monocytes can serve as alternative sites for 1,25(OH)2D3 conversion.
• To explore the role of 1-alpha hydroxylase (CYP27B1) activity in monocytes during tuberculosis infection.

Main Methods:

• An ex vivo bioassay was used to measure 1-alpha hydroxylase (CYP27B1) activity in monocytes.
• Monocytes were obtained from patients with active tuberculosis (TB) and individuals with frequent TB contact.
• Monocyte activity was assessed with and without restimulation with Mycobacterium tuberculosis antigen.

Main Results:

• Monocytes from patients with active TB showed significantly higher CYP27B1 activity compared to those with frequent TB contact.
• Restimulation of monocytes from active TB patients with M. tuberculosis antigen led to decreased 1,25(OH)2D3 levels.
• Monocytes from individuals with frequent TB contact showed unchanged 1,25(OH)2D3 levels upon antigen restimulation.

Conclusions:

• Monocytes possess 1-alpha hydroxylase (CYP27B1) activity, suggesting they are an alternative site for converting 25-hydroxyvitamin D3 to 1,25(OH)2D3.
• Tuberculosis infection influences monocyte-mediated vitamin D activation, potentially contributing to hypercalcemia in affected patients.