Tight junctions during inflammation affect paracellular transport by doing what?

Tight junctions during inflammation affect paracellular transport by doing what?

• A. Loosening tight junctions increases permeability
• B. Tight junctions become tighter
• C. Membrane cholesterol decreases
• D. Increases vesicular transport

Answer: (A)

Inflammation loosens the barrier between cells, changing how easily substances can pass through the paracellular route. Tight junctions normally seal the spaces between adjacent cells, but inflammatory signals release cytokines that activate signaling pathways, notably myosin light chain kinase. This triggers contraction of the perijunctional actomyosin ring and remodeling of the tight junctions, widening the paracellular pores. As a result, ions, small solutes, and even immune cells can move more readily between cells to reach sites of infection or injury. So, the key idea is that inflammation disrupts tight junctions, increasing paracellular permeability. The alternative ideas—tightening the junctions, altering membrane cholesterol, or promoting vesicular (transcellular) transport—do not describe the observed paracellular changes during inflammation.

Inflammation loosens the barrier between cells, changing how easily substances can pass through the paracellular route. Tight junctions normally seal the spaces between adjacent cells, but inflammatory signals release cytokines that activate signaling pathways, notably myosin light chain kinase. This triggers contraction of the perijunctional actomyosin ring and remodeling of the tight junctions, widening the paracellular pores. As a result, ions, small solutes, and even immune cells can move more readily between cells to reach sites of infection or injury.

So, the key idea is that inflammation disrupts tight junctions, increasing paracellular permeability. The alternative ideas—tightening the junctions, altering membrane cholesterol, or promoting vesicular (transcellular) transport—do not describe the observed paracellular changes during inflammation.