PURPOSE: Wallerian degeneration (WD) is an antegrade degenerative process distal to peripheral nerve injury. Numerous genes are differentially regulated in response to the process. However, the underlying mechanism is unclear, especially the early response. We aimed at investigating the effects of sciatic nerve injury on WD via CLDN 14/15 interactions in vivo and in vitro. METHODS: Using the methods of molecular biology and bioinformatics analysis, we investigated the molecular mechanism by which claudin 14/15 participate in WD. Our previous study showed that claudins 14 and 15 trigger the early signal flow and pathway in damaged sciatic nerves. Here, we report the effects of the interaction between claudin 14 and claudin 15 on nerve degeneration and regeneration during early WD. RESULTS: It was found that claudin 14/15 were upregulated in the sciatic nerve in WD. Claudin 14/15 promoted Schwann cell proliferation, migration and anti-apoptosis in vitro. PKCα, NT3, NF2, and bFGF were significantly upregulated in transfected Schwann cells. Moreover, the expression levels of the β-catenin, p-AKT/AKT, p-c-jun/c-jun, and p-ERK/ERK signaling pathways were also significantly altered. CONCLUSION Claudin 14/15 affect Schwann cell proliferation, migration, and anti-apoptosis via the β-catenin, p-AKT/AKT, p-c-jun/c-jun, and p-ERK/ERK pathways in vitro and in vivo. The results of this study may help elucidate the molecular mechanisms of the tight junction signaling pathway underlying peripheral nerve degeneration.
Animals ; Claudins ; Nerve Regeneration ; Peripheral Nerve Injuries ; Rats ; Schwann Cells/pathology* ; Sciatic Nerve ; Wallerian Degeneration/pathology*

OBJECTIVETo investigate systematically Schwann cell apoptosis in Wallerian-degenerated sciatic nerve of the rat, and evaluate its time-related feature.

METHODSNinety-five SD rats were divided randomly into one normal group (8 rats) and 11 experimental groups (66 rats, 6 in each). Both hind legs of each rat in experimental groups were randomly divided into test leg (sciatic nerve transected) and control one (nerve uninjured). All test legs constituted a test group and all control legs constituted a control one. After operation, all rats were respectively sacrificed at 1 h, 6 h, 12 h, 24 h, 2 d, 3 d, 4 d, 8 d, 14 d, 21 d, and 30 d. We analyzed the specimens of mid-distal sciatic nerve, especially the morphological changes of the nerve, the different expression levels of S-100 protein and apoptosis-related proteins such as Bcl-2, Bax, and Fas in Schwann cells. The TUNEL method was used to detect the apoptotic rate of Schwann cells.

RESULTS(1) The test group showed Wallerian degeneration. The number of Schwann cells began to decrease at 24 h, obviously decreased on day 3 and 4, then began to increase from day 8 and formed Bungner belt after 14 days. (2) Schwann cells generally expressed S-100 at a low level in all groups. The control group was not significantly different from the normal group. The test group had statistical significance at 1 h and day 21. (3) As an inhibitory gene protein of Schwann cell apoptosis, Bcl-2 positive rates in the control and test groups apparently elevated and were statistically different from the normal group. (4) As a promotive gene protein of Schwann cell apoptosis, the control and test groups expressed Bax at a high level and were statistically different from the normal group. (5) As a promotive gene protein of Schwann cell apoptosis, Fas positive rate in control group was slightly elevated, but had no statistical significance compared with the normal group. Fas positive rate in test group continuously elevated in a fluctuant way, with highly statistical significance compared with the normal group. (6) TUNEL detection further proved that Schwann cell apoptosis rarely existed in the normal group, and the left sciatic nerve had no statistical significance compared with the right sciatic nerve. While the test group showed lots of apoptotic nuclei at 6 h, 2 d, 4 d, and 21 d. It had highly statistical significance compared with the normal group.

CONCLUSIONSSchwann cell apoptosis does exist in Wallerian-degenerated sciatic nerve of the rat after transection. Schwann cell apoptosis and its apoptotic genes expression have a time-related feature.

Analysis of Variance ; Animals ; Apoptosis ; Female ; In Situ Nick-End Labeling ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Schwann Cells ; pathology ; Sciatic Nerve ; pathology ; Staining and Labeling ; Wallerian Degeneration ; pathology

OBJECTIVETo study the effects of intranigral injection of different doses of CuSO4.5H2O on dopaminergic neuron in the nigrostriatal system of rats.

METHODSWistar rats were divided into four groups, including control group, 10 nmol, 50 nmol and 200 nmol copper injected into left substantia nigra (SN) groups. Seven days after the intranigral injection of copper, dopamine (DA) contents in the striatum (Str) were measured by high performance lipid chromotophotography (HPLC); the density of tyrosine hydroxylase (TH) positive axons in the Str was measured by TH staining method; TH and Caspase-3 mRNA expression in the SN were measured by semi-quantitative RT-PCR. We detected the activity of superoxide dismutase (SOD) in the lesioned midbrain of rats using biochemical methods.

RESULTSDA and its metabolites contents had no significant difference between control group and low dose (10 nmol) copper group. But from 50 nmol copper group, DA contents in the lesioned sides were reduced with the increase in the copper doses injected, showing a significant linear correlation (F = 34.16, P < 0.01). In the 50 nmol copper group, TH positive axons in the Str decreased compared with those of the control and unlesioned sides (F = 121.9, P < 0.01). In the 50 nmol copper group, TH mRNA expression decreased (t = 3.12, P < 0.01) while Caspase-3 mRNA expression increased (t = 8.96, P < 0.01) in the SN compared with the control. SOD activity decreased in the midbrain of rats treated with 50 nmol copper compared with that of the control (t = 2.33, P < 0.01).

CONCLUSIONCopper could induce damage of dopaminergic neurons in the SN of rats through destroying antioxidant defenses and promoting apoptosis.

Animals ; Apoptosis ; drug effects ; physiology ; Axons ; drug effects ; metabolism ; pathology ; Caspase 3 ; drug effects ; genetics ; metabolism ; Copper ; toxicity ; Corpus Striatum ; drug effects ; metabolism ; pathology ; Dopamine ; metabolism ; Dose-Response Relationship, Drug ; Male ; Nerve Degeneration ; chemically induced ; metabolism ; pathology ; Neural Pathways ; drug effects ; metabolism ; pathology ; Neurons ; drug effects ; metabolism ; pathology ; Neurotoxins ; toxicity ; Oxidative Stress ; drug effects ; physiology ; Parkinsonian Disorders ; chemically induced ; metabolism ; physiopathology ; RNA, Messenger ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Substantia Nigra ; drug effects ; metabolism ; pathology ; Superoxide Dismutase ; drug effects ; genetics ; metabolism ; Superoxide Dismutase-1 ; Tyrosine 3-Monooxygenase ; drug effects ; genetics ; metabolism ; Wallerian Degeneration ; chemically induced ; metabolism ; pathology