Lipoprotein lipase is expressed in rat sciatic nerve and regulated in response to crush injury

Male adult Sprague-Dawley rats were subjected to unilateral crush injury, and expression of LPL protein and mRNA were assessed as a function of time post-crush. LPL activity increased in the distal portion of the injured nerve by Day 4 post-crush, after which LPL activity gradually returned to normal levels. Conversely, quantification of LPL mRNA by reverse transcription-polymerase chain reaction demonstrated unchanged or decreased LPL mRNA in the distal nerve. Immunohistochemical analysis of LPL protein expression using an anti-rat LPL antibody revealed that LPL protein is present throughout the endoneurium of the sciatic nerve and increases in abundance following crush injury. The possibility that infiltrating macrophages are responsible for the increase in LPL protein levels in the crush injured nerve was addressed by immunohistochemical staining for ED-1, a differentiated macrophage marker protein. ED-1 was minimally present in the uninjured nerve and was detected at Day 4 post-crush, suggesting that the increase in LPL protein and activity that occurs following crush injury is at least partly derived from macrophages. These data suggest a role for LPL in the response of peripheral nerves to crush injury, possibly in order to facilitate reutilization of lipids from degenerating myelin.