| Peripheral nerve injury often leads to various degrees of permanent dysfunction. The internal environment of nerve fibers changes with peripheral nerve injury and is affected by a variety of local factors (including cytokines and humoral factors), which directly or indirectly impact injury and regeneration reactions of peripheral nerves. Compared to the body’s fluids, seawater provides a hypertonic, high-sodium, and high-alkali environment. Although studies have shown that seawater immersion aggravates damage to a variety of human organs and tissues, it is still unknown whether it increases peripheral nerve injury or delays neuronal recovery. In crush injury, in which there is contusion and laceration caused by open injuries, nerve tissues can directly be in contact with seawater and this immersion in seawater may in a way participate in and influence the development of the pathophysiological processes after nerve injury. The conditions may be more serious in sciatic nerve injury. In this study we first established a rat sciatic nerve crush injury model with seawater immersion.We observed the impact of seawater immersion on neuronal recovery following sciatic nerve injury and the recovery rate of gastrocnemius wet weight and pathological changes of sciatic nerve in rats through three different staining methods.We also observed the protection of methylprednisolone of promoting the regeneration of sciatic nerve in rats with seawater immersion.On this basis, changes in contents of reactive oxygen species (ROS), malondialdehyde (MDA), inducile nitric oxide synthase (iNOS), interleukin-1β(IL-1β), interleukin-6(IL-6), tumor necrosis factor alpha(TNF-α) in injured nerve tissues were detected to explore the possible mechanism of sciatic nerve secondary injury caused by seawater immersion and the protection of methylprednisolone and provide an important theoretical basis for further clinical treatment.The study is divided in two parts. In the first experiment, a total of 234 Sprague-Dawley male rats were randomly divided into sham group, injury control group, and seawater immersion + injury group. The Sciatic Functional Index (SFI) was used to assess nerve function for 6 wk after injury. Compound muscle action potentials were measured and hematoxylin and eosin (HE) staining,silver staining and Luxol Fast Blue staining of nerve specimens was carried out at 6 wk. Levels of reactive oxygen species (ROS) and malondialdehyde (MDA) in nerve tissues were measured by ELISA, and inducible nitric oxide synthase (iNOS) mRNA and protein expression were measured by RT-PCR and immunohistochemistry, respectively. The results showed that, the SFI in the seawater immersion+injury group after 6 wk was lower than in the injury group (P< 0.05). The compound muscle action potential in the seawater immersion + injury group had a prolonged latency, and the amplitude and nerve conduction velocity were decreased compared with the other groups (P< 0.05). HE staining,silver staining and Luxol Fast Blue staining showed nerve fiber regeneration was worse in the seawater immersion + injury group. ROS and MDA levels in the seawater immersion+injury group were higher than in the other groups (P< 0.05). Expression of iNOS mRNA and protein gradually increased in the injury and seawater immersion + injury groups and peaked at 48 h after surgery. These results suggested that immersion in seawater further aggravated sciatic nerve injury, and led to worse neuronal recovery. The mechanism may be associated with oxidative stress and nitrosative stress.In the second experiment, A total of 192 Sprague-Dawley rats were randomly divided into group A(sham group), group B(injury control group), group C(seawater immersion + injury group), group D(methylprednisolone group). The Sciatic Functional Index (SFI) was used to assess nerve function after injury, the recovery rate of gastrocnemius wet weight was to evaluate the degree of muscle atrophy at 3d、1w、2w、4w,HE staining was to observe the pathological morphological changes of sciatic nerve at 4w and IL-1β、IL-6、TNF-amRNA and protein expression were measured by RT-PCR and immunohistochemistry respectively. The results showed that, The SFI in group B、 C、D was gradually increased from 3 days to 4 weeks after operation. Group C was lower than group B and Group D was higher than group C (P< 0.05). The gastrocnemius muscle wet weight recovery is the best in group B, group C is the worst and the group A had no obvious change. HE staining showed nerve fiber regeneration was worse in the group C, Group D was better than group C.The expression of IL-1β、 IL-6、TNF-amRNA in group A was little at 3 days、1 week、2 weeks、4 weeks after operation. The expression of IL-1β、 IL-6mRNA in group B、C、D was gradually decreased from 3 days to 4 weeks after operation. The expression of TNF-amRNA in group B、C、D was gradually decreased from 3 days to 2 weeks after operation and there was no change at 2 weeks、4 weeks after operation.The mean value of integral optical density of expression of IL-1β、 IL-6、TNF-α protein in group A were lowest at 3 days、1 week、2 weeks、4 weeks after operation. The mean value of integral optical density of expression of IL-1β、IL-6、TNF-a protein in group B、C、D were supreme at 3 days、1 week after operation, while at 2 weeks the grade of expression of IL-1β、IL-6 protein were cut down,and TNF-a protein was lowest.The expression of IL-1β、IL-6、TNF-α protein in group B、C、D were lowest at 4 weeks after operation.These results suggested that seawater immersion increased the expression of IL-1β, IL-6 and TNF-α after sciatic nerve injury in rat,which caused inflammation, hindered the recovery of nerve function. Methylprednisolone promoted the regeneration of sciatic nerve in rats with seawater immersion, probably act by inhibiting inflammatory reaction. In summary, immersion in seawater further aggravated sciatic nerve injury, and led to worse neuronal recovery. The mechanism may be associated with oxidative stress and nitrosative stress. Seawater immersion increased the expression of IL-1β, IL-6 and TNF-α after sciatic nerve injury in rat,which caused inflammation, hindered the recovery of nerve function. Methylprednisolone promoted the regeneration of sciatic nerve in rats with seawater immersion,probably act by inhibiting inflammatory reaction. |
PDF Full Text Request