Permanent occlusion of the middle cerebral artery upregulates expression of cytokines and neuronal nitric oxide synthase in the spinal cord and urinary bladder in the adult rat

Transsynaptic degeneration of ventral horn motor neurons exists but plays a minor role in lower motor system dysfunction in acute ischemic rats

BACKGROUND

As a leading cause of mortality and long-term disability, acute ischemic stroke can produce far-reaching pathophysiological consequences. Accumulating evidence has demonstrated abnormalities in the lower motor system following stroke, while the existence of Transsynaptic degeneration of contralateral spinal cord ventral horn (VH) neurons is still debated.

METHODS

Using a rat model of acute ischemic stroke, we analyzed spinal cord VH neuron counts contralaterally and ipsilaterally after stroke with immunofluorescence staining. Furthermore, we estimated the overall lower motor unit abnormalities after stroke by simultaneously measuring the modified neurological severity score (mNSS), compound muscle action potential (CMAP) amplitude, repetitive nerve stimulation (RNS), spinal cord VH neuron counts, and the corresponding muscle fiber morphology. The activation status of microglia and extracellular signal-regulated kinase 1/2 (ERK 1/2) in the spinal cord VH was also assessed.

RESULTS

At 7 days after stroke, the contralateral CMAP amplitudes declined to a nadir indicating lower motor function damage, and significant muscle disuse atrophy was observed on the same side; meanwhile, the VH neurons remained intact. At 14 days after focal stroke, lower motor function recovered with alleviated muscle disuse atrophy, while transsynaptic degeneration occurred on the contralateral side with elevated activation of ERK 1/2, along with the occurrence of neurogenic muscle atrophy. No apparent decrement of CMAP amplitude was observed with RNS during the whole experimental process.

CONCLUSIONS

This study offered an overview of changes in the lower motor system in experimental ischemic rats. We demonstrated that transsynaptic degeneration of contralateral VH neurons occurred when lower motor function significantly recovered, which indicated the minor role of transsynaptic degeneration in lower motor dysfunction during the acute and subacute phases of focal ischemic stroke.

Endothelial immunocytochemical expression of pituitary IL-1β and its relation to ACTH-positive cells is regulated by corticosterone in the male rat

Interleukin-1 beta (IL-1β) is a cytokine linking the neuroendocrine system and metabolic homeostasis. We have previously demonstrated the relevance of IL-1β for maintaining the pituitary ACTH-producing cells by immuno-blocking its effects in pituitary cultures. However, the morphological characteristics and the intimate relationship of the pituitary cells expressing IL-1β and ACTH remain unknown. For determining pituitary variations of immunoreactivity for IL-1β and its relation with ACTH-positive cells under stress situations, we performed an immunohistochemical analysis of the expression of IL-1β and ACTH in the pituitary gland of adult rats, in the absence or presence of corticosterone, by establishing different groups: untreated, sham-operated, and bilaterally adrenalectomized animals. In the rats subjected to surgery, the glucocorticoid was administered on the same day of the intervention and on the third day post-surgery. Interestingly, it was observed that IL-1β was located in the pituitary endothelial cells at the hypophyseal portal vessels, regardless of the treatment schedule. When comparing the pituitary immunoreactive surface to IL-1β expression without corticosterone, adrenalectomized animals displayed a significantly greater area than the sham-operated animals. Corticosterone significantly inhibited the effect of adrenalectomy depending on the time interval it was administered. By in situ hybridization, IL-1β mRNA expression was also correlated with immnunocytochemical expression of pituitary IL-1β. Our results demonstrate that IL-1β is a constitutive element in endothelial portal pituitary vessels and under stress experimental conditions IL-1β increases its expression and its relation with ACTH-positive cells, suggesting that IL-1β could participate in an autocrine-paracrine fashion thereby modulating the pituitary population of ACTH-positive cells.

Apocynin Attenuates Cerebral Infarction after Transient Focal Ischaemia in Rats

This study investigated whether inhibition of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase attenuates cerebral infarction after transient focal ischaemia in rats. Focal ischaemia (1.5 h) was produced in male Sprague-Dawley rats (250 − 280 g) by middle cerebral artery occlusion. Some rats also received treatment with 50 mg/kg apocynin, a NADPH oxidase inhibitor, by intraperitoneal injection 30 min prior to reperfusion. Two hours after reperfusion, brains were harvested to measure NADPH oxidase activity and superoxide levels. After 24 h, the remaining brains were harvested to investigate infarct size. NADPH oxidase activity and superoxide level were all augmented 2 h after reperfusion compared with controls. Apocynin treatment significantly reduced NADPH oxidase activity and superoxide levels. Cerebral infarct size was significantly smaller in the apocynin-treated group compared with those undergoing ischaemia/reperfusion alone. These results indicate that inhibition of NADPH oxidase attenuates cerebral infarction after transient focal ischaemia in rats, suggesting that inhibition of NADPH oxidase may provide a therapeutic strategy for ischaemic stroke.

The GLP-1 receptor agonists exendin-4 and liraglutide alleviate oxidative stress and cognitive and micturition deficits induced by middle cerebral artery occlusion in diabetic mice

Background

Glucagon-like peptide 1 (GLP-1) analogs protect a variety of cell types against oxidative damage and vascular and neuronal injury via binding to GLP-1 receptors. This study aimed to investigate the effects of the GLP-1 analogs exendin-4 and liraglutide on cerebral blood flow, reactive oxygen species production, expression of oxidative stress-related proteins, cognition, and pelvic sympathetic nerve-mediated bladder contraction after middle cerebral artery occlusion (MCAO) injury in the db/db mouse model of diabetes.

Results

Sixty minutes of MCAO increased blood and brain reactive oxygen species counts in male db/db mice, as revealed by dihydroethidium staining. MCAO also increased nuclear factor-κB and intercellular adhesion molecule-1 expression and decreased cerebral microcirculation. These effects were attenuated by treatment with exendin-4 or liraglutide. MCAO did not affect basal levels of phosphorylated Akt (p-Akt) or endothelial nitric oxide synthase (p-eNOS); however, exendin-4 and liraglutide treatments significantly enhanced p-Akt and p-eNOS levels, indicating activation of the p-Akt/p-eNOS signaling pathway. MCAO-induced motor and cognitive deficits and micturition dysfunction, indicated by reduced pelvic nerve-mediated voiding contractions and increased nonvoiding contractions, were also partially attenuated by exendin-4 treatment.

Conclusions

The above data indicate that treatment with GLP-1 agonists exerts protective effects against oxidative, inflammatory, and apoptotic damage in brain areas that control parasympathetic/pelvic nerve-mediated voiding contractions and cognitive and motor behaviors in a diabetic mouse model.

Blood-Spinal Cord Barrier Alterations in Subacute and Chronic Stages of a Rat Model of Focal Cerebral Ischemia

We previously demonstrated blood-brain barrier impairment in remote contralateral brain areas in rats at 7 and 30 days after transient middle cerebral artery occlusion (tMCAO), indicating ischemic diaschisis. Here, we focused on effects of subacute and chronic focal cerebral ischemia on the blood-spinal cord barrier (BSCB). We observed BSCB damage on both sides of the cervical spinal cord in rats at 7 and 30 days post-tMCAO. Major BSCB ultrastructural changes in spinal cord gray and white matter included vacuolated endothelial cells containing autophagosomes, pericyte degeneration with enlarged mitochondria, astrocyte end-feet degeneration and perivascular edema; damaged motor neurons, swollen axons with unraveled myelin in ascending and descending tracts and astrogliosis were also observed. Evans Blue dye extravasation was maximal at 7 days. There was immunofluorescence evidence of reduction of microvascular expression of tight junction occludin, upregulation of Beclin-1 and LC3B immunoreactivities at 7 days and a reduction of the latter at 30 days post-ischemia. These novel pathological alterations on the cervical spinal cord microvasculature in rats after tMCAO suggest pervasive and long-lasting BSCB damage after focal cerebral ischemia, and that spinal cord ischemic diaschisis should be considered in the pathophysiology and therapeutic approaches in patients with ischemic cerebral infarction.

Research Findings on Overactive Bladder

Several physiopathologic conditions lead to the manifestation of overactive bladder (OAB). These conditions include ageing, diabetes mellitus, bladder outlet obstruction, spinal cord injury, stroke and brain injury, Parkinson's disease, multiple sclerosis, interstitial cystitis, stress and depression. This review has discussed research findings in human and animal studies conducted on the above conditions. Several structural and functional changes under these conditions have not only been observed in the lower urinary tract, but also in the brain and spinal cord. Significant changes were observed in the following areas: neurotransmitters, prostaglandins, nerve growth factor, Rho-kinase, interstitial cells of Cajal, and ion and transient receptor potential channels. Interestingly, alterations in these areas showed great variation in each of the conditions of the OAB, suggesting that the pathophysiology of the OAB might be different in each condition of the disease. It is anticipated that this review will be helpful for further research on new and specific drug development against OAB.

Alterations in the time course of expression of the Nox family in the brain in a rat experimental cerebral ischemia and reperfusion model: effects of melatonin

Ischemia-reperfusion (I/R) injury induces the generation of reactive oxygen species (ROS), which results in a poor prognosis for ischemic stroke patients. This study was designed to evaluate the time course of expression of the Nox family, a major source of ROS, and whether melatonin, a potent scavenger of ROS, influences these parameters in a rat model of cerebral I/R caused by middle cerebral artery occlusion (MCAO). After 2-hr occlusion, the filament was withdrawn to allow reperfusion. At 0, 3, 6, 12, 24, and 48 hr after reperfusion, brain tissue samples were obtained for assays. Among the Nox family, the mRNA and protein levels of Nox2 and Nox4 were increased both in the ischemic hemisphere and contralateral counterpart in the experimental I/R rats at 0 hr after reperfusion, peaked at 3 hr, and then returned to the basal level at 24 hr. Double-immunofluorescence staining further confirmed the expressions of Nox2 and Nox4 in three major types of brain cells, including neurons, astrocytes, and endothelial cells. In addition, melatonin (5 mg/kg) or its vehicle was injected intraperitoneally at 0.5 hr before MCAO. Compared with I/R + vehicle group, melatonin pretreatment diminished the increased expression of Nox2 and Nox4, reduced ROS levels, and inhibited cell apoptosis. Our findings suggested that the inhibition of Nox2 and Nox4 expressions by melatonin may essentially contribute to its antioxidant and anti-apoptotic effects during brain I/R.

A substance P antagonist improves outcome when administered 4 h after onset of ischaemic stroke

Previous studies have suggested that substance P (SP) plays a critical role in the development of brain oedema and functional deficits following traumatic brain injury and that SP receptor antagonism may improve outcome. No studies have described such a role in ischemic stroke. The present study characterized the effects of the NK1 tachykinin receptor antagonist, n-acetyl-L-tryptophan (NAT), on blood-brain barrier (BBB) breakdown, oedema formation, infarct volume and functional outcome following reversible ischemic stroke in rats. Ischemia was induced using a reversible thread model of middle cerebral artery occlusion where occlusion was maintained for 2 h before reperfusion. Animals received either NAT or equal volume saline vehicle intravenously at 2 h post-reperfusion. Ischaemic stroke resulted in increased perivascular SP immunoreactivity at 24 h. Administration of NAT significantly reduced oedema formation and BBB permeability at 24 h post-ischemia and significantly improved functional outcome as assessed over 7 days. There was no effect on infarct volume. We conclude that inhibition of SP activity with a NK1 tachykinin receptor antagonist is effective in reducing cerebral oedema, BBB permeability and functional deficits following reversible ischemia and may therefore represent a novel therapeutic approach to the treatment of ischaemic stroke.

Immunomodulatory effect of Hawthorn extract in an experimental stroke model

BACKGROUND

Recently, we reported a neuroprotective effect for Hawthorn (Crataegus oxyacantha) ethanolic extract in middle cerebral artery occlusion-(MCAO) induced stroke in rats. The present study sheds more light on the extract's mechanism of neuroprotection, especially its immunomodulatory effect.

METHODS

After 15 days of treatment with Hawthorn extract [100 mg/kg, pretreatment (oral)], male Sprague Dawley rats underwent transient MCAO for 75 mins followed by reperfusion (either 3 or 24 hrs). We measured pro-inflammatory cytokines (IL-1β, TNF-α, IL-6), ICAM-1, IL-10 and pSTAT-3 expression in the brain by appropriate methods. We also looked at the cytotoxic T cell sub-population among leukocytes (FACS) and inflammatory cell activation and recruitment in brain (using a myeloperoxidase activity assay) after ischemia and reperfusion (I/R). Apoptosis (TUNEL), and Bcl-xL- and Foxp3- (T(reg) marker) positive cells in the ipsilateral hemisphere of the brain were analyzed separately using immunofluorescence.

RESULTS

Our results indicate that occlusion followed by 3 hrs of reperfusion increased pro-inflammatory cytokine and ICAM-1 gene expressions in the ipsilateral hemisphere, and that Hawthorn pre-treatment significantly (p ≤ 0.01) lowered these levels. Furthermore, such pre-treatment was able to increase IL-10 levels and Foxp3-positive cells in brain after 24 hrs of reperfusion. The increase in cytotoxic T cell population in vehicle rats after 24 hrs of reperfusion was decreased by at least 40% with Hawthorn pretreatment. In addition, there was a decrease in inflammatory cell activation and infiltration in pretreated brain. Hawthorn pretreatment elevated pSTAT-3 levels in brain after I/R. We also observed an increase in Bcl-xL-positive cells, which in turn may have influenced the reduction in TUNEL-positive cells compared to vehicle-treated brain.

CONCLUSIONS

In summary, Hawthorn extract helped alleviate pro-inflammatory immune responses associated with I/R-induced injury, boosted IL-10 levels, and increased Foxp3-positive T(regs) in the brain, which may have aided in suppression of activated inflammatory cells. Such treatment also minimizes apoptotic cell death by influencing STAT-3 phosphorylation and Bcl-xL expression in the brain. Taken together, the immunomodulatory effect of Hawthorn extract may play a critical role in the neuroprotection observed in this MCAO-induced stroke model.

Secondary damage in the spinal cord after motor cortex injury in rats

When neurons within the motor cortex are fatally injured, their axons, many of which project into the spinal cord, undergo wallerian degeneration. Pathological processes occurring downstream of the cortical damage have not been extensively studied. We created a focal forelimb motor cortex injury in rats and found that axons from cell bodies located in the hindlimb motor cortex (spared by the cortical injury) become secondarily damaged in the spinal cord. To assess axonal degeneration in the spinal cord, we quantified silver staining in the corticospinal tract (CST) at 1 week and 4 weeks after the injury. We found a significant increase in silver deposition at the thoracic spinal cord level at 4 weeks compared to 1 week post-injury. At both time points, no degenerating neurons could be found in the hindlimb motor cortex. In a separate experiment, we showed that direct injury of neurons within the hindlimb motor cortex caused marked silver deposition in the thoracic CST at 1 week post-injury, and declined thereafter. Therefore, delayed axonal degeneration in the thoracic spinal cord after a focal forelimb motor cortex injury is indicative of secondary damage at the spinal cord level. Furthermore, immunolabeling of spinal cord sections showed that a local inflammatory response dominated by partially activated Iba-1-positive microglia is mounted in the CST, a viable mechanism to cause the observed secondary degeneration of fibers. In conclusion, we demonstrate that following motor cortex injury, wallerian degeneration of axons in the spinal cord leads to secondary damage, which is likely mediated by inflammatory processes.

EGb761 protects motoneurons against avulsion-induced oxidative stress in rats

BACKGROUND

Root avulsion of the brachial plexus causes an oxidative stress reaction in the spinal cord and induces dramatic spinal motoneuron death, while EGb761 is a natural free radical cleaning agent. This study was designed to investigate the protective effects of intraperitoneally injected EGb761 against neural damage following brachial root avulsion.

METHODS

The effect of EGb761 on avulsion-induced motoneuron injury was studied in 26 total groups of (n) rats, treated as follows. Animals in singular number groups received EGb761(50 mg/kg.d) and those in complex number groups received normal saline solution (i.p.), serving as controls. Groups 1-8 were used for the determination of nitric oxide (NO) levels in the serum and injured spinal cord at the 5 d, 2 w, 4 w, and 6 w time points. Groups 9-16 were used for determination of constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) levels in injured spinal cord at the 5 d, 2 w, 4 w, and 6 w time points. Groups 17-26 were used for determination of the number of neuronal nitric oxide synthase (nNOS)-positive and surviving motoneurons in injured C7 ventral horn at the 5 d, 2 w, 4 w, 6 w and 8 w time points.

RESULTS

Compared to control groups, the EGb761 treatment group not only had significant decreased levels of NO in serum at 2 w and 6 w after avulsion, but also had reduced levels of NO specifically in the spinal cord at 2 w, 4 w and 6 w. The cNOS activity in the spinal cord was also significant decreased at 2 w and 4 w, while the iNOS activity in injured C6-T1 spinal segments was reduced at 2 w, 4 w and 6 w. All together, the percentages of NADPH-d positive motoneurons in an injured C7 segment were down-regulated and the number of surviving motoneurons in injured C7 ventral horn was increased at 2 w, 4 w, 6 w and 8 w in treated versus untreated animals.

CONCLUSIONS

Intraperitoneal administration of EGb761 after root avulsion of the brachial plexus exerted protective effects by decreasing the level of NO in spinal cord and serum and the activity of cNOS and iNOS, easing the delayed motoneurons death. EGb761 should be considered in the treatment of brachial plexus nerve injuries.

Transient middle cerebral artery occlusion induces microglial priming in the lumbar spinal cord: a novel model of neuroinflammation

Background

Middle cerebral artery occlusion (MCAo) in mice results in a brain infarct, the volume of which depends on the length of occlusion. Following permanent occlusion, neuropathological changes – including a robust glial inflammatory response – also occur downstream of the infarct in the spinal cord.

Methods

We have performed short, transient MCAo in mice to induce penumbral damage spanning the motor cortex. A 30 minute MCAo using a poly-L-lysine-coated intraluminal suture introduced through a common carotid artery incision was performed in 17 female C57BL/6 mice. Five sham-operated mice received common carotid artery ligation without insertion of the suture. Neurobehavioural assessments were performed during occlusion, immediately following reperfusion, and at 24 and 72 hours post-reperfusion. Routine histological and immunohistochemical studies were performed at 24 and 72 hours.

Results

In 11 of the surviving 16 mice subjected to MCAo, we observed a focal, subcortical necrotic lesion and a reproducible, diffuse cortical lesion with accompanying upper motor neuron involvement. This was associated with contralateral ventral spinal cord microglial priming without significant reactive astrocytosis or lower motor neuron degeneration.

Conclusion

The advantages to this method are that it yields a reproducible cortical lesion, the extent of which is predictable using behavioural testing during the period of ischemia, with upper motor neuron involvement and downstream priming, but not full activation, of microglia in the lumbar spinal cord. In addition, survival is excellent following the 30 minutes of occlusion, rendering this a novel and useful model for examining the effects of microglial priming in the spinal motor neuron pool.

Activation of interleukin-1 beta (IL-1 beta) signaling in the spinal cord in the rats with experimental cardiac injury

BACKGROUND

The involvement of central nervous system (CNS) interleukin-1 beta (IL-1 beta) in the pathogenesis of acute cardiac injury is still an unexplored issue. The present study was aimed to investigate whether cardiac injury could induce the activation of IL-1 beta in the spinal cord.

METHODS AND RESULTS

Cardiac injury model in rats was established by intra-myocardial injection of formalin through the diaphragm. Western blot showed that IL-1 beta was upregulated in the upper thoracic spinal cord following cardiac injury. The upregulated IL-1 beta was distributed in the dorsal and ventral horns in the thoracic spinal cord as determined by immunohistochemistry. In situ hybridization demonstrated that IL-1 beta mRNA localized in the neurons was elevated in response to cardiac injury. The DNA binding activities of two IL-1 beta transcription factors, activator protein (AP)-1 and nuclear factor kappa B (NF-kappaB), were enhanced after cardiac injury. In correlated with the upregulation of the spinal IL-1 beta, the circulating IL-1 beta level was also increased following cardiac injury.

CONCLUSIONS

Acute cardiac injury could activate the spinal IL-1 beta signaling, which, in turn, may contribute to disease progression in the acute phase of cardiac injury in clinical practice.

Neurological manifestations in Fabry's disease

Fabry's disease is an X-linked lysosomal storage disorder caused by a defect in the gene that encodes the lysosomal enzyme alpha-galactosidase A. Symptoms arise because of accumulation of globotriaosylceramide in multiple organs, resulting in severely reduced quality of life and premature death. Neurological symptoms, such as burning sensations (occasionally accompanied by acroparesthesia) and stroke, are among the first to appear, and occur in both male and female patients. A delay in establishing the diagnosis of Fabry's disease can cause unnecessary problems, especially now that enzyme replacement treatment is available to prevent irreversible organ damage. Females with Fabry's disease who present with pain have often been ignored and misdiagnosed because of the disorder's X-linked inheritance. This Review will stress the importance of recognizing neurological symptoms for the diagnosis of Fabry's disease. The possible pathophysiological background will also be discussed.

NADPH-oxidase activity is elevated in penumbral and non-ischemic cerebral arteries following stroke

Reactive oxygen species play a role in neuronal damage following cerebral ischemia-reperfusion. We tested whether activity of the superoxide-generating enzyme, NADPH-oxidase, is enhanced in cerebral arteries within, adjacent and distant from the ischemic core. The right middle cerebral artery (MCA) of conscious rats was temporarily occluded by perivascular injection of endothelin-1 to induce stroke (ET-1; n=19). Control rats were injected with saline (n=9). At 24 h or 72 h post-administration of ET-1, the MCA and its branches within the ipsilateral penumbra and infarcted core, corresponding arteries in the contralateral hemisphere, and basilar artery were excised. Anatomically similar arteries were excised from saline-injected rats. At 24 h after stroke, NADPH-stimulated superoxide production by arteries from the infarcted core did not differ from levels generated by arteries from control rats, whereas levels were significantly lower 72 h after stroke. However, at both time points after stroke, superoxide production by arteries from the ischemic penumbra was 8-fold greater than levels generated by arteries from control rats. Surprisingly, even in the non-ischemic arteries from the contralateral hemisphere and in the basilar artery, superoxide production was increased approximately 4- to 6-fold at 24 h, but had returned to normal 72 h after stroke. The NADPH-oxidase inhibitor, diphenyleneiodonium, virtually abolished superoxide production by all arteries. Thus, the activity of NADPH-oxidase is enhanced in cerebral arteries from the ischemic penumbra at 24 h and 72 h following cerebral ischemia. Additionally, NADPH-oxidase activity is temporarily enhanced after cerebral ischemia within arteries from non-ischemic parts of the brain.

Glial activation and segmental upregulation of interleukin-1beta (IL-1beta) in the rat spinal cord after surgical incision

The present study investigated the expression patterns of glial cells and interleukin-1beta (IL-1beta) in the rat spinal cord after a surgical incision, which is closely related with clinical postoperative pain. Microglia and astrocytes became activated in the spinal cord following incision. Real-time polymerase chain reaction (PCR) and immunohistochemisty showed that IL-1beta mRNA and protein level in the spinal cord was transiently upregulated after surgical incision. The increased IL-1beta-immunoreactivity (IR) was mainly localized in neurons but not the activated microglia or astrocytes. Although obvious increase in IL-1beta-IR could be observed in the lumbar segments of the spinal cord ipsilateral to a hind paw incision, significant upregulation of IL-1beta was not detected in the lumbar segments following thoracic incision. The present study indicated that surgical incision could induce glial activation and segmental upregulation of IL-1beta in the spinal cord. The activated glial cells and upregulated IL-1beta, in turn, may be involved in the incision-induced pain hypersensitivity.

Experimental stroke induces massive, rapid activation of the peripheral immune system

Clinical experimental stroke induces injurious local brain inflammation. However, effects on the peripheral immune system have not been well characterized. We quantified mRNA and protein levels for cytokines, chemokines, and chemokine receptors (CCR) in brain, spinal cord, peripheral lymphoid organs (spleen, lymph node, blood, and cultured mononuclear cells from these sources), and blood plasma after reversible middle cerebral artery occlusion (MCAO) or sham treatment in male C57BL/6 mice. Middle cerebral artery occlusion induced a complex, but organ specific, pattern of inflammatory factors in the periphery. At both 6 and 22 h after MCAO, activated spleen cells from stroke-injured mice secreted significantly enhanced levels of TNF-alpha, IFN-gamma, IL-6, MCP-1, and IL-2. Unstimulated splenocytes expressed increased chemokines and CCR, including MIP-2 and CCR2, CCR7 and CCR8 at 6 h; and MIP-2, IP-10, and CCR1 and CCR2 at 22 h. Also at 22 h, T cells from blood and lymph nodes secreted increased levels of inflammatory cytokines after activation. As expected, there were striking proinflammatory changes in postischemic brain. In contrast, spinal cord displayed suppression of all mediators, suggesting a compensatory response to intracranial events. These data show for the first time that focal cerebral ischemia results in dynamic and widespread activation of inflammatory cytokines, chemokines, and CCR in the peripheral immune system.

Calcium-dependent expression of TNF-α in neural cells is mediated by the calcineurin/NFAT pathway

We report induction of TNF-alpha via the calcium/calcineurin/NFAT pathway in PC12 neural cells. In PC12, expression of TNF-alpha mRNA, protein and TNF-alpha gene promoter activity was induced by co-stimulation with phorbol ester and either calcium ionophore A23187 or the L-type Voltage Gated Calcium Channel agonist Bay K 8644. Pre-treatment with calcineurin inhibitors CsA or FK506 inhibited the dominant calcium-dependent component of this induction, limiting it to the level achieved with phorbol ester alone. Promoter activation by Bay was abolished by nifedipine, a specific inhibitor of L-type Voltage Gated Calcium Channels. Exogenous NFAT protein transactivated the TNF-alpha promoter, and the peptide VIVIT-a specific inhibitor of calcineurin/NFAT binding-blocked calcium-inducible transactivation of the TNF-alpha promoter. Given proposed functions of TNF-alpha in spatial learning, memory and the pathogenesis of neurodegenerative diseases, the data presented suggest an important role for calcineurin/NFAT signaling in these key neurological processes.

Inflammation of rat dorsal root ganglia below a mid-thoracic spinal transection

Macrophages and T-lymphocytes invade the spinal cord in and around a lesion and spinal microglia are converted into macrophages. After spinal transection at T8 in rats, T-lymphocyte and major histocompatibility complex II+ (MHC II+) macrophage numbers were increased within dorsal root ganglia (DRGs) below the lesion. Inflammation was greater in DRGs closer to the site of transection. After 8 weeks, MHC II+cell density had fallen by 30% but T-lymphocyte numbers were undiminished. In lumbosacral DRGs, inflammation preceded inflammation within the spinal cord. The responses in distant DRGs are hard to reconcile with the limited damage to sensory neurons produced by the lesion. Inflammation of DRGs after spinal injury may contribute to hyper-reflexia and pain.