Neural thrombin and protease nexin I kinetics after murine peripheral nerve injury.
We addressed the balance between thrombin and its serpin protease nexin I (PNI) after sciatic nerve injury in the mouse. Prothrombin levels increased twofold 24 h after nerve crush, as measured by a specific chromogenic assay, and peaked at day 3. Thrombin activity also increased 2-4 days after injury in distal sciatic nerve segments. Nerve RNA analysis using reverse transcriptase--polymerase chain reaction (RT-PCR) assay confirmed that prothrombin was synthesized locally. We also monitored PNI levels in these injured nerve samples by complex formation with an 125I-labeled target protease and found peak activity occurring later, 6-9 days after the thrombin induction. These data indicate that nerve injury first induces the synthesis of prothrombin, which is subsequently converted to active thrombin. Nerve crush-induced thrombin is followed by the generation of functionally active PNI and may be directly responsible for its induction. By immunocytochemistry with anti-PNI antibody, we found that activated Schwann cells were the source of induced PNI. These results support the concept that the balance between serine proteases and their serpins is dysregulated during nerve injury and suggests a role for its reestablishment in nerve damage repair.
Smirnova
I V
IV
Neurobiology Research Laboratory, Department of Veterans Affairs Medical Center, Kansas City, Missouri 64128, USA.
Ma
J Y
JY
Citron
B A
BA
Ratzlaff
K T
KT
Gregory
E J
EJ
Akaaboune
M
M
Festoff
B W
BW
D016564:Amyloid beta-Protein Precursor; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis*; D017931:DNA Primers; D005260:Female; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D009409:Nerve Crush; D010960:Plasminogen Activators / Q000378:metabolism; D016133:Polymerase Chain Reaction; D058255:Protease Nexins; D011516:Prothrombin / Q000378:metabolism; D011956:Receptors, Cell Surface; D012584:Sciatic Nerve / Q000293:injuries* / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000096:biosynthesis*; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis*; D013917:Thrombin / Q000096:biosynthesis*; D013997:Time Factors; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D017931:DNA Primers; D058255:Protease Nexins; D011956:Receptors, Cell Surface; D015842:Serine Proteinase Inhibitors; D011516:Prothrombin; D010960:Plasminogen Activators; D012697:Serine Endopeptidases; D013917:Thrombin; D014568:Urokinase-Type Plasminogen Activator