Ortho substituted polychlorinated biphenyls elevate intracellular [Ca(2+)] in human granulocytes

Area of Science:

• Environmental Toxicology
• Immunology
• Cellular Physiology

Background:

• Polychlorinated biphenyls (PCBs) are environmental contaminants with known immunotoxic effects.
• Disruption of cellular calcium (Ca2+) homeostasis is a critical mechanism in toxicity.

Purpose of the Study:

• To investigate the effects of ortho and non-ortho substituted PCBs on Ca2+ homeostasis in human granulocytes.
• To elucidate the mechanisms underlying PCB-induced Ca2+ perturbations.

Main Methods:

• Exposure of human granulocytes to various PCB congeners.
• Measurement of intracellular free Ca2+ levels ([Ca2+]i).
• Assessment of the role of external Ca2+, phospholipase C, and inositol trisphosphate (Ins(1,4,5)P3).

Main Results:

• Ortho-substituted PCBs increased [Ca2+]i in a concentration-dependent manner.
• The effect was inversely related to the surface area of the PCB congener.
• Most ortho-substituted PCBs required external Ca2+ and phospholipase C activation, except for 2,2',6,6'-TeCB.
• A potential mechanism involves phospholipase C activation, Ins(1,4,5)P3 production, and subsequent Ca2+ release and channel activation.

Conclusions:

• Ortho-substituted PCBs significantly elevate intracellular Ca2+ in human granulocytes.
• This Ca2+ dysregulation may contribute to the observed immunomodulatory effects of PCBs.
• PCBs may activate Ca2+ signaling pathways directly or indirectly, impacting immune cell function.