The expression of proinflammatory cytokine mRNA in the sciatic-tibial nerve of ischemia-reperfusion injury

Therapeutic effects of masitinib on abnormal mechanoreception in a mouse model of tourniquet-induced extremity ischemia-reperfusion

Tourniquets are widely used to stop extremity hemorrhage, but their use and subsequent release can result in nerve damage and degeneration, leading to neurological deficits. Increasing evidence has suggested a pivotal role of inflammation in nerve damage and abnormal mechanoreception. In this study, we investigated the therapeutic effects of masitinib (Mas), an anti-neuroinflammatory drug, on the mechanoreception of sensory neurons in a mouse model of tourniquet-induced hind paw ischemia-reperfusion (tourniquet/IR). C57BL/6 mice were subjected to 3 h of ischemia by placing a rubber band at the ankle joint and evaluated for subsequent reperfusion injury on day 1, 3, 7, 14, and 28 based on the experiments. Treatment with Mas (28 mg/kg/day, i.p.) began on the day of IR induction and lasted for 1, 3, 7, 14, or 28 days. Tourniquet/IR caused sensory nerve denervation in the skin of paw pads and abolished the hind paw mechanoreception to mechanical stimulation during the first 3 days of reperfusion. Sensory nerves gradually reinnervated in the skin of paw pads and allodynia began to appear on day 7. The maximum reaction occurred on day 14 and was maintained throughout the study period. Treatment with Mas mitigated nerve damage and improved hind paw mechanoreception to mechanical stimulation by decreasing the production of reactive oxygen species (ROS) during the early stages of tourniquet/IR. Mas also alleviated allodynia and decreased inflammatory cytokines (IL-1β and TNFα) in the skin of paw pads from days 7-28. Our data suggest that treatment with Mas significantly ameliorated paw numbness and allodynia in mouse hind paw tourniquet/IR.

Effect of Taxifolin on Ischemia/Reperfusion-Induced Oxidative Injury of Sciatic Nerve in Rats

BACKGROUND

Ischemia is a condition in which blood flow to tissues is decreased or entirely stopped for various reasons. The reperfusion process exacerbates damage caused by ischemia in the organs and tissues. Reactive oxygen species (ROS) are mainly responsible for ischemia-reperfusion (IR) damage. ROS increase results in lipid peroxidation (LPO) and oxidative stress. In the literature, taxifolin reportedly suppresses ROS production. This study aimed to determine the effect of taxifolin, which is a flavonoid, on IR injury of the sciatic nerve in rats.

METHODS

This study divided 30 albino Wistar rats into 3 groups: IR without medication (IR) group, taxifolin applied IR (TAX+IR) group, and only dissection made to the sciatic nerve sham group (SHAM). Sciatic nerve injury was induced by applying 2 hours of ischemia and 3 hours of reperfusion to the abdominal aorta and iliolumbar arteries. Biochemical and histopathologic investigations then were performed on sciatic nerve tissues. Malondialdehyde, total glutathione, glutathione reductase, and glutathione peroxidase were analyzed as oxidative stress markers, and tumor necrosis factor-α and interleukin-1β levels were evaluated as inflammatory stress markers in biochemical tests.

RESULTS

The IR group has statistically significantly high oxidant and cytokine levels and low antioxidant levels compared with the TAX+IR group. Taxifolin treatment was also shown to cause significant histopathologic improvement.

CONCLUSIONS

We suggest that taxifolin may be effective in preventing IR injury of the sciatic nerve.

Impact of aortic cross-clamping time on peripheral nerves: experimental model

PURPOSE

The present study investigated the correlation between extend aortic cross-clamping time and peripheral nerve injury on rats.

METHODS

24 male, Sprague Dawley rats were divided into 3 groups; (a) control group: abdomen was directly closed after reached aorta, and followed by 72 hours, (b) short-term ischaemia-reperfusion group: peripheral nerve ischemia was induced in rats by supraceliac aortic occlusion for 20 min followed by 72 h of reperfusion, (c) long-term ischaemia-reperfusion group: peripheral nerve ischemia was induced for 30 min followed by 72 h of reperfusion. Preoperative and postoperative, electromyography (EMG) recordings were done. End of 72 h, the sciatic nerves were harvested from each animal for histopathological and biochemical analysis.

RESULTS

The mean compound muscle action potential (CMAP) amplitude of long-term ischaemia-reperfusion group was statically significant reduced when compared to the control group (p <0.01). However, the mean distal latency value of long-term ischaemia-reperfusion group was statically significant increased (p <0.01). On the other hand, there were statically significant differences between the results of malondialdehyde, edema and ischemia fiber degeneration grades on control and long-term ischaemia-reperfusion group (p <0.001).

CONCLUSION

This study demonstrated that the extending cross clamping time directly harms the peripheral nerve of rats.

Bone marrow expression of poly(ADP-ribose) polymerase underlies diabetic neuropathy via hematopoietic-neuronal cell fusion

Diabetic neuropathy is the most common diabetic complication. The pathogenetic pathways include oxidative stress, advanced glycation end product (AGE) formation, protein kinase C, and NF-κB activation, as well as increased polyol flux. These metabolic perturbations affect neurons, Schwann cells, and vasa nervorum, which are held to be the primary cell types involved. We hypothesize that diabetes induces the appearance of abnormal bone marrow-derived cells (BMDCs) that fuse with neurons in the dorsal root ganglia (DRG) of mice, leading to diabetic neuropathy. Neuronal poly(ADP-ribose) polymerase-1 (PARP-1) activation in diabetes is known to generate free radical and oxidant-induced injury and poly(ADP-ribose) polymer formation, resulting in neuronal death and dysfunction, culminating in neuropathy. We further hypothesize that BM-specific PARP expression plays a determining role in disease pathogenesis. Here we show that bone marrow transplantation (BMT) of PARP-knockout (PARPKO) cells to wild-type mice protects against, whereas BMT of wild-type cells to PARPKO mice, which are normally "neuropathy-resistant," confers susceptibility to, diabetic neuropathy. The pathogenetic process involving hyperglycemia, BMDCs, and BMDC-neuron fusion can be recapitulated in vitro. Incubation in high, but not low, glucose confers fusogenicity to BMDCs, which are characterized by proinsulin (PI) and TNF-α coexpression; coincubation of isolated DRG neurons with PI-BMDCs in high glucose leads to spontaneous fusion between the 2 cell types, while the presence of a PARP inhibitor or use of PARPKO BMDCs in the incubation protects against BMDC-neuron fusion. These complementary in vivo and in vitro experiments indicate that BMDC-PARP expression promotes diabetic neuropathy via BMDC-neuron fusion.

Inflammatory mediators in diabetic and non-diabetic lumbosacral radiculoplexus neuropathy

Nerve microvasculitis and ischemic injury appear to be the primary and important pathogenic alterations in lumbosacral radiculoplexus neuropathy of patients with (DLRPN) and without (LRPN) diabetes mellitus (DM). Here, we examine the involvement of inflammatory mediators in DLRPN and LRPN. Paraffin sections of sural nerves from 19 patients with DLRPN, 13 patients with LRPN, and 20 disease control patients were immunostained for intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and nuclear factor kappaB (NF-kappaB). The findings were correlated with histopathology. The pathologic and immunohistochemical alterations of DLRPN and LRPN nerves were indistinguishable. The nerves of both types of LRPN had a significantly greater number of ICAM-1 positive vessels than did the controls (P < 0.01). TNF-alpha expression was seen in Schwann cells and some macrophages of DLRPN and LRPN nerves, whereas IL-6 expression was minimal. There was greater NF-kappaB immunoreactivity in vessels and endoneurial cells of DLRPN and LRPN nerves than of the controls (P < 0.001). NF-kappaB expression correlated with the number of empty nerve strands (P < 0.01) and the frequency of axonal degeneration (P < 0.05), whereas TNF-alpha expression correlated inversely with the number of empty nerve strands of teased fibers (P < 0.05). Our findings suggest that up-regulation of inflammatory mediators target different cells at different disease stages and that these mediators may be sequentially involved in an immune-mediated inflammatory process that is shared by both DLRPN and LRPN. Up-regulated inflammatory mediators may be immunotherapeutic targets in these two conditions.

Decreased peripheral nerve damage after ischemia-reperfusion injury in mice lacking TNF-alpha

We sought to explore the role of tumor necrosis factor-alpha (TNF-alpha) in the pathogenesis of peripheral nerve ischemia-reperfusion (IR) injury. We established an ischemia-reperfusion model in wild type (WT) and TNF-alpha knockout (KO) mice. Electrophysiology, behavioral score and morphological indices (edema and ischemic fiber degeneration [IFD]) were examined to determine the influence of TNF-alpha on peripheral nerve structure and function following ischemia followed by reperfusion. TNF-alpha and nuclear factor-kappa B (NF-kappaB) expression were evaluated using immunohistochemistry. TNF-alpha KO mice, compared to WT had, in sciatic nerve, marked improvement in nerve pathology. This is a region subject to moderate ischemia-reperfusion injury. There was also a significant improvement in electrophysiological and some behavioral indices. TNF-alpha and NF-kappaB expression were abundant in sciatic-tibial nerves of WT mice subjected to IR, but there was less, or complete lack of, expression in ischemic nerve of TNF-alpha KO mice. We conclude that TNF-alpha plays an essential role in the pathogenesis of peripheral nerve ischemia-reperfusion injury, possibly partly through the activation of NF-kappaB.

Orchestration of the inflammatory response in ischemia-reperfusion injury

Ischemia to nerve can cause fiber degeneration and reperfusion following ischemia [ischemia-reperfusion (IR)] adds the additional insult of an inflammatory response and oxidative injury. Limited information is available on the molecular mediators and their endoneurial targets. In this study, using a highly reproducible animal model of IR injury to nerve and selective immunolabeling methods [for nuclear factor kappa B (NF-kappaB), intercellular adhesion molecule-1 (ICAM-1), cytokines, and inflammatory cells] over an expanded time frame, we evaluated the temporal pattern and localization of mediators of the inflammatory response. Sixty rats were used. Nine groups (N=6 each) underwent complete hind limb ischemia for 4 h, followed by reperfusion durations of 0, 3, 12, 24, and 48 h, and 7, 14, 28, and 42 days. One group underwent sham operation (N=6). The earliest change was ICAM-1 expression in the microvessel (endothelial cell) followed almost immediately by NF-kappaB activation with axonal expression (24 and 48 h), followed by endoneurial edema and ischemic fiber degeneration (7 and 14 days). Granulocytic infiltration was followed by endoneurial infiltration of mononuclear phagocytes (14 days), expression of interleukin 6 (IL-6) (microvessels), and subsequent Schwann cell NF-kappaB expression. Granulocytes, tumor necrosis factor alpha, and IL-6-positive cells were observed primarily within the epineurium. IR results in changes in a number of interacting networks of targets and inflammatory mediators. NF-kappaB activation has a central orchestrating role involving both the axon and the Schwann cell in effecting the inflammatory response.

Ischemic preconditioning reduces the severity of ischemia-reperfusion injury of peripheral nerve in rats

Background and aim

Allow for protection of briefly ischemic tissues against the harmful effects of subsequent prolonged ischemia is a phenomennon called as Ischemic Preconditioning (IP). IP has not been studied in ischemia-reperfusion (I/R) model of peripheral nerve before. We aimed to study the effects of acute IP on I/R injury of peripheral nerve in rats.

Method

70 adult male rats were randomly divided into 5 groups in part 1 experimentation and 3 groups in part 2 experimentation. A rat model of severe nerve ischemia which was produced by tying iliac arteries and all idenfiable anastomotic vessels with a silk suture (6-0) was used to study the effects of I/R and IP on nerve biochemistry. The suture technique used was a slip-knot technique for rapid release at time of reperfusion in the study. Cytoplasmic vacuolar degeneration was also histopathologically evaluated by light microscopic examination in sciatic nerves of rats at 7th day in part 2 study.

Results

3 hours of Reperfusion resulted in an increase in nerve malondialdehyde levels when compared with ischemia and non-ischemia groups (p < 0.001 and p < 0.0001 respectively). IP had significantly lower nerve MDA levels than 3 h reperfusion group (p < 0.001). The differences between ischemic, IP and non-ischemic control groups were not significant (p > 0.05). There was also a significant decrease in vacoular degeneration of sciatic nerves in IP group than I/R group (p < 0.05).

Conclusion

IP reduces the severity of I/R injury in peripheral nerve as shown by reduced tissue MDA levels at 3 th hour of reperfusion and axonal vacoulization at 7 th postischemic day.

Enhanced inflammatory response via activation of NF-kappaB in acute experimental diabetic neuropathy subjected to ischemia-reperfusion injury

Reperfusion following ischemia increases ischemic fiber degeneration (IFD) in diabetic nerves compared to control normoglycemic nerves. The mechanism of this excessive susceptibility is unclear. Since reperfusion injury results in an inflammatory response, we tested the hypothesis that the diabetic state increases the inflammatory cascade. We used an animal model of unilateral ischemia-reperfusion (IR) injury to streptozotocin (STZ)-induced diabetic nerve to evaluate the density and localization of mediators of the inflammatory response using selective immunolabeling methods (for nuclear factor kappa B (NF-kappaB), intercellular adhesion molecule-1 (ICAM-1), cytokines and inflammatory cells). We studied a 1-month diabetic group and an age-matched control group (n=6 each). The right limb underwent 3 h ischemia at 35 degrees C and 7 days reperfusion. This was achieved by ligating the supplying arteries and collaterals to the right sciatic-tibial nerve for 3 h, followed by releasing the ties. Immunohistochemistry was performed on proximal sciatic and mid tibial nerves. NF-kappaB expression in diabetic sciatic endothelial cell and Schwann cell (SC) was significantly increased over that of controls subjected to identical IR injury. We observed a nearly 2-fold increase in density of NF-kappaB and ICAM-1 expression in microvessels of diabetic nerve compared with control nerve. Extensive infiltration of monocyte macrophages (1C7) was observed in the endoneurium of diabetic nerves, while only mild infiltration of granulocytes (HIS 48) occurred in the endoneurium of diabetic tibial nerves. This study provides evidence for an enhanced inflammatory response in diabetic nerves subjected to IR injury apparently via NF-kappaB activation.

The fusion of bone-marrow-derived proinsulin-expressing cells with nerve cells underlies diabetic neuropathy

Diabetic neuropathy is the most common microvascular complication of diabetes. Here we show that, in streptozotocin-induced diabetic rodents with neuropathy, a subpopulation of bone-marrow-derived cells marked by proinsulin expression migrates to and fuses with neurons in the sciatic nerve and dorsal root ganglion (DRG), resulting in neuronal dysfunction and accelerated apoptosis. The absence or presence of proinsulin expression, which identifies the fusion cells, and not the disease state (nondiabetic vs. diabetic) of the rats from which the DRG neurons are isolated determines whether the DRG neurons show normal or abnormal calcium homeostasis and apoptosis. These results suggest that bone-marrow-derived cells may play an important role in the pathogenesis of diabetic complications.

Inhibition of inducible nitric oxide synthase promotes recovery of motor function in rats after sciatic nerve ischemia and reperfusion

PURPOSE

To investigate the effects of inhibition of inducible nitric oxide synthase (iNOS) on the recovery of motor function in the rat sciatic nerve after ischemia and reperfusion injury.

METHODS

A 10-mm segment of the sciatic nerve from 169 rats had 2 hours of ischemia followed by up to 42 days of reperfusion. The animals were divided into 2 groups that received either iNOS inhibitor 1400W or the same volume of sterile water subcutaneously. A walking track test was used to evaluate the motor functional recovery during reperfusion. Statistical analysis was performed for the measurements of the sciatic functional index (SFI) by using 2-way analysis of variance; 1-way analysis of variance was used for the post hoc analysis of specific values at each time point of the SFI measurement.

RESULTS

1400W-treated rats had earlier motor functional recovery than controls, with a significantly improved SFI between days 11 and 28. Histology showed less axonal degeneration and earlier regeneration of nerve fibers in the 1400W group than in the controls. Inducible NOS messenger RNA and protein were up-regulated during the first 3 days of reperfusion but there was a down-regulation of neuronal NOS and up-regulation of endothelial NOS in control animals. 1400W treatment attenuated the increase of iNOS but had no effect on neuronal NOS and endothelial NOS.

CONCLUSIONS

Our results indicate that early inhibition of iNOS appears to be critical for reducing or preventing ischemia and reperfusion injury.

Ischemia–reperfusion injury of peripheral nerve in experimental diabetic neuropathy

The pathogenesis of human diabetic neuropathy likely involves the interplay of hyperglycemia, ischemia, and oxidative stress. Mild-moderate ischemia-reperfusion to streptozotocin (STZ)-induced diabetes results in florid fiber degeneration in diabetic but not in normal nerves. Uncertainty exists as to the influence of duration of diabetes on this susceptibility. We therefore studied diabetic tibial and sciatic nerves using a rat ischemia-reperfusion (IR) model after 1 month and 4 months of diabetes utilizing electrophysiological, behavioral, and neuropathological methods. Electrophysiological abnormalities were present in 1-month diabetic rats (D) and persisted over 4 months. Behavioral scores were decreased markedly at 4 months (p<0.05). Endoneurial edema and ischemia fiber degeneration (IFD) were observed at both the 1-month (p<0.01 and p<0.001) and 4-month (p<0.001) durations in diabetic nerves, whereas only mild or no damage was observed in age-matched control nerves. These findings demonstrate that STZ-induced diabetes exacerbates the morphological and electrophysiological pathology in peripheral nerve to IR injury both in the early timepoint of 1 month and late timepoint of 4 months, although there was a gradation of injury, which is more severe at the later timepoint. Reperfusion exaggerated morphological pathology in 1-month STZ-induced diabetic peripheral nerve.

Schwann cell is a target in ischemia-reperfusion injury to peripheral nerve

Ischemia-reperfusion (IR) causes oxidative injury and ischemic fiber degeneration due to injury of the neuron and axon. In this study, we explore the effect of oxidative stress on Schwann cells, as a specific peripheral nerve target, using our established rat model for IR injury. Fifty-six rats were used. Six groups (N = 8 each) underwent complete hindlimb ischemia for 4 h, followed by reperfusion durations of 0 h, 3 h, 7 days, 14 days, 28 days, and 42 days. One group underwent sham operation (N = 8). We evaluated immunohistochemical labeling for oxidative injury using anti-8-hydroxydeoxyguanosine (8-OHdG). To identify cells committed to apoptosis, we studied immunolabeling to caspase-3 and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) positivity. Only minimal positivity was seen in the sham, 0-h, and 3-h groups. Positivity to 8-OHdG, caspase-3, and TUNEL increased significantly in groups undergoing longer reperfusion (8-OHdG, 7-28 days; caspase-3, 14-42 days; TUNEL, 14-42 days). The positive cells surrounding axons were identified as being Schwann cells by their configuration and colabeling with S-100. We conclude that apoptosis of Schwann cells occurs during reperfusion and continues even when axons regenerate. Schwann cell apoptosis could contribute to impairment of axonal function and efficiency of fiber regeneration. Both these abnormalities are known to occur in experimental and human diabetic nerves.

Peripheral nerve ischemia: reperfusion injury and fiber regeneration

We continued our studies of ischemia-reperfusion (IR) injury, extending the reperfusion duration to 42 days to capture the fiber regeneration process. We used a rat model for IR injury produced by ligation and release of nooses around supplying vessels to the sciatic nerve. Fifty-six rats were used. One group (control N = 8) underwent sham ischemia; the other six groups (N = 8 each) underwent complete hind limb ischemia for 4 h followed by reperfusion durations of 0 h (ischemia alone), 3 h, 7 days, 14 days, 28 days, and 42 days. Behavioral and electrophysiological data were obtained immediately before euthanasia. Pathologically, three phases were identifiable: Phase 1 (0-3 h)-minimal pathological changes, minimal edema; phase 2 (7 days, 14 days)-prominent fiber degeneration, endoneurial edema; phase 3 (28 days, 42 days)-abundant small regenerating fiber clusters, minimal edema. Compound muscle action potential (CMAP) was the most sensitive index of neural deficits and recovery, showing progressive recovery beyond 14 days. Severe functional deficits developed immediately and persisted with a trend to recovery at the 42-day time-point. It was concluded that reperfusion, by oxidative injury, worsened nerve function and aggravated fiber degeneration, but in the longer time frame, permitted fiber regeneration to occur.

Neuroprotective effects of nitrone radical scavenger S-PBN on reperfusion nerve injury in rats

The nitrone-based free radical scavengers have potent neuroprotective activities in models of stroke in which oxidative stress plays a key role in its development. We examined the effects of S-PBN (sodium 4-[(tert-butylimino) methyl]benzene-3-sulfonate N-oxide), a spin trap nitrone, on reperfusion injury in rat peripheral nerves. Immediately after the onset of 4-h ischaemia in rat right hindlimb, S-PBN was administered via mini-osmotic pumps, containing 2 ml of S-PBN (1.2 M), inserted subcutaneously. S-PBN, in addition, was given by a single injection (50 mg/kg BW, i.p.). Mean plasma concentrations of S-PBN were significantly greater in S-PBN-treated rats than in controls after 24, 48 and 72 h of reperfusion. Pump and dosing solution analysis indicated that the rats received between 82 and 99% of the target S-PBN concentration. Morphology in sciatic, tibial and peroneal nerves was assessed after 4 h of ischaemia followed by 72 h and 7 days of reperfusion. After 72 h of reperfusion, saline-treated control rats showed endoneurial oedema at the thigh level and diffuse axonal degeneration of myelinated nerve fibres distally. S-PBN-treated nerves were normal or revealed less severe abnormalities in myelinated fibres after 72 h and 7 days of reperfusion, when compared with those in saline-treated control nerves. Morphometrically, the frequency of abnormal myelinated fibres at calf levels was significantly less in S-PBN-treated nerves than in controls. In conclusion, post-ischaemic administration of S-PBN exhibits substantial neuroprotective properties in ischemia/reperfusion nerve injury.

Ischemia-reperfusion of the murine testis stimulates the expression of proinflammatory cytokines and activation of c-jun N-terminal kinase in a pathway to E-selectin expression

Ischemia-reperfusion (IR) of the testis results in germ cell-specific apoptosis and can lead to aspermatogenesis. Germ cell-specific apoptosis after IR of the testis has been shown to be correlated with and dependent on neutrophil recruitment to the testis after IR. Studies that used E-selectin-deficient mice have demonstrated that E-selectin expression is critical for neutrophil recruitment to subtunical venules in the testis after IR and for the resultant germ cell-specific apoptosis. The present study investigates the in vivo signaling pathway that exists after IR that leads to neutrophil recruitment in the murine testis. Mice were subjected to a 2-h period of testicular ischemia followed by reperfusion. Results demonstrate that the proinflammatory cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta), are stimulated after IR as is the phosphorylation of c-jun N-terminal kinase (JNK). The downstream transcription factors of JNK, ATF-2 and c-jun are also phosphorylated at specific times after IR of the testis. Activation of the JNK stress-related kinase pathway is correlated with an increase in E-selectin expression and neutrophil recruitment to the testis after IR. Intratesticular injection of IL-1beta also caused JNK phosphorylation and neutrophil recruitment to the testis. These results suggest that testicular IR injury stimulates IL-1beta expression, which leads to activation of the JNK signaling pathway and ultimately E-selectin expression and neutrophil recruitment to the testis. This provides the first evidence of a cytokine/stress-related kinase signaling pathway to E-selectin expression in vivo.

Complete Freund's adjuvant suppresses the development and progression of pristane-induced arthritis in rats

The present study produced the novel finding that treatment with a nonarthritogenic dose of Complete Freund's adjuvant (CFA) before the onset of pristane-induced arthritis (PIA) could prevent the development of PIA. Surprisingly, treatment with nonarthritogenic and arthritogenic doses of CFA could almost cure the ongoing PIA. CFA treatment also suppressed pathological changes, such as inflammatory cell infiltration, pannus formation, bone destruction, and new bone formation. The lymph node cells of rats with PIA suppressed by CFA showed significantly increased mRNA expression of IFN-gamma but no significant changes in mRNA expression of IL-2, TNF-alpha, IL-4, and IL-5 compared with those of rats in the control groups. The possible mechanisms of the suppressive effect of CFA on the development and progression of PIA were discussed in terms of the anti-inflammatory roles of IFN-gamma, nitric oxide, and heat-shock protein-specific T cell responses. The present study found a new therapeutic implication for the treatment of rheumatoid arthritis.

Aggravated reperfusion injury in STZ-diabetic nerve

The streptozocin (STZ)-diabetic nerve manifests increased morphological susceptibility to a superimposed acute ischemic injury, and reperfusion injury exaggerates ischemic nerve pathology. To determine whether STZ-diabetic nerves are susceptible to reperfusion, we evaluated the pathological consequences after 2.5 hours of ischemia followed by 3 and 24 hours of reperfusion in a 20-week STZ-diabetic rat sciatic nerve. After 3 hours of reperfusion, endoneurial edema developed in diabetic nerves, whereas non-diabetic controls showed mild or no edema. Morphometric analysis of endoneurial edema, quantified by the total transverse fascicular area and the point-count score of endoneurial structureless space, confirmed significantly more reperfusion-induced edema at thigh and knee levels in diabetic nerves than in controls. Reperfusion caused a significant increase in the number of endoneurial mast cells at the thigh level in diabetic nerves. After 24 hours of reperfusion, there were striking morphological anomalies of myelinated nerve fibers in diabetic nerves, without any observable changes in control nerves. In conclusion, we have demonstrated that STZ-diabetes exacerbates the morphological change to reperfusion. Diabetes therefore renders the microvasculature more vulnerable to the deleterious effects of ischemia/reperfusion.

Balance of Th1/Th2 cytokines associated with the preventive effect of incomplete Freund's adjuvant on the development of adjuvant arthritis in LEW rats

Complete Freund's adjuvant (CFA) could induce adjuvant arthritis (AA) in LEW rats and incomplete Freund's adjuvant (IFA) could induce oil induced arthritis (OIA) in DA but not in LEW rats. Lymph node cells (LNCs) from these AA and OIA rats showed increased mRNA expression of IFN-gamma, IL-2 and TNF-alpha but not IL-4. LNCs from IFA immunized LEW rats showed increased expression of IL-4, reduced expression of IFN-gamma and TNF-alpha and no IL-2, in contrast to IFA immunized DA rats. The pretreatment of IFA before CFA challenge could completely prevent AA in LEW rats and their LNCs showed increased expression of IL-4 and IFN-gamma but not IL-2 and TNF-alpha. In F1 (LEW x DA) rats, IFA could not induce OIA but the pretreatment of IFA before CFA challenge could induce very mild AA with 80% incidence, LNCs showing an elevated expression of all the above cytokines. These findings suggest that increased Th1 cytokine expression is associated with disease development and that increased IL-4 expression or the balance of Th2 over Th1 cytokine expression plays an important regulatory role in disease development.

Pro- and Anti-inflammatory Cytokine Gene Expression in Rat Sciatic Nerve Chronic Constriction Injury Model of Neuropathic Pain

Cytokines may be pathophysiologically involved in hyperalgesia. Uncertainty exists about the types of cytokines and their site of action. To study the role of key pro- and anti-inflammatory cytokines in a chronic constriction model of neuropathic pain, mRNA expression of TNF, IL-1beta, IL-6, and IL-10 was quantified using competitive RT-PCR. Each cytokine mRNA in rat sciatic nerve was examined at days 3, 7, 14, and 45 after chronic constriction injury (CCI). We also undertook behavioral testing of these rats. Thermal warming and touch thresholds were significantly reduced at days 3, 7, and 14 in the CCI group, compared with the sham-operated group. Cytokine gene expression in sciatic nerve was significantly increased at day 7 for IL-1beta and IL-6 and at day 14 for TNF. Expression of IL-10 underwent a gradual and progressive increase, reaching statistical significance at day 45.

Egr-1, a master switch coordinating upregulation of divergent gene families underlying ischemic stress

Activation of the zinc-finger transcription factor early growth response (Egr)-1, initially linked to developmental processes, is shown here to function as a master switch activated by ischemia to trigger expression of pivotal regulators of inflammation, coagulation and vascular hyperpermeability. Chemokine, adhesion receptor, procoagulant and permeability-related genes are coordinately upregulated by rapid ischemia-mediated activation of Egr-1. Deletion of the gene encoding Egr-1 strikingly diminished expression of these mediators of vascular injury in a murine model of lung ischemia/reperfusion, and enhanced animal survival and organ function. Rapid activation of Egr-1 in response to oxygen deprivation primes the vasculature for dysfunction manifest during reperfusion. These studies define a central and unifying role for Egr-1 activation in the pathogenesis of ischemic tissue damage.