Systemic microcirculation after complete high and low thoracic spinal cord section in rats

Longitudinal Impact of Acute Spinal Cord Injury on Clinical Pharmacokinetics of Riluzole, a Potential Neuroprotective Agent

Riluzole, a benzothiazole sodium channel blocker that received US Food and Drug Administration approval to attenuate neurodegeneration in amyotrophic lateral sclerosis in 1995, was found to be safe and potentially efficacious in a spinal cord injury (SCI) population, as evident in a phase I clinical trial. The acute and progressive nature of traumatic SCI and the complexity of secondary injury processes can alter the pharmacokinetics of therapeutics. A 1-compartment with first-order elimination population pharmacokinetic model for riluzole incorporating time-dependent clearance and volume of distribution was developed from combined data of the phase 1 and the ongoing phase 2/3 trials. This change in therapeutic exposure may lead to a biased estimate of the exposure-response relationship when evaluating therapeutic effects. With the developed model, a rational, optimal dosing scheme can be designed with time-dependent modification that preserves the required therapeutic exposure of riluzole.

Thoracic sympathetic nuclei ischemia: Effects on lower heart rates following experimentally induced spinal subarachnoid hemorrhage

BACKGROUND

The neuropathological mechanism of heart rhythm disorders, following spinal cord pathologies, to our knowledge, has not yet been adequately investigated. In this study, the effect of the ischemic neurodegeneration of the thoracic sympathetic nuclei (TSN) on the heart rate (HR) was examined following a spinal subarachnoid hemorrhage (SSAH).

METHODS

This study was conducted on 22 rabbits. Five rabbits were used as a control group, five as SHAM, and twelve as a study group. The animals' HRs were recorded via monitoring devices on the first day, and those results were accepted as baseline values. The HRs were remeasured after injecting 0.5 cc of isotonic saline for SHAM and 0.5 cc of autolog arterial blood into the thoracic spinal subarachnoid space at T4-T5 for the study group. After a three-week follow-up with continuous monitoring of their HRs, the rabbit's thoracic spinal cords and stellate ganglia were extracted. The specimens were evaluated by histopathological methods. The densities of degenerated neurons in the TSN and stellate ganglia were compared with the HRs.

RESULTS

The mean HRs and mean degenerated neuron density of the TSN and stellate ganglia in control group were 251±18/min, 5±2/mm³, and 3±1/mm³, respectively. The mean HRs and the mean degenerated neuron density of the TSN and stellate ganglia were detected as 242±13/min, 6±2/mm³, and 4±2/mm³ in SHAM (P>0.05 vs. control); 176±19/min, 94±12/mm³, and 28±6/mm³ in the study group (P<0.0001 vs. control and P<0.005 vs. SHAM), respectively.

CONCLUSIONS

SAH induced TSN neurodegeneration may have been responsible for low HRs following SSAH. To date this has not been mentioned in the literature.

Pharmacokinetics and anti-inflammatory effect of naproxen in rats with acute and subacute spinal cord injury

Previous reports have warned about the influence of spinal cord injury (SCI) on the pharmacokinetics of various drugs. However, the role of SCI in the efficacy and safety of pharmacotherapy remains unknown. Thereby, our aim was to explore the role of SCI on pharmacokinetics and anti-inflammatory effect of naproxen in response to a local inflammatory challenge. Rats received a severe contusive SCI at T9 or sham injury. Pharmacokinetics of a single intravenous dose of naproxen (10 mg kg^-1) was studied at days 1 and 15 post-surgery. For the anti-inflammatory assessment, carrageenan was subcutaneously injected in forelimb and hindlimb paws at the same post-surgery periods, and naproxen efficacy was evaluated measuring paw swelling. Plasma protein concentrations and body weight changes were also determined. Plasma naproxen levels and pharmacokinetic parameters were unchanged by acute injury, but subacute injury generated alterations in volume of distribution, clearance, and bioavailability, resulting in significantly reduced plasma naproxen concentrations, in the absence of changes in plasma proteins. Assessment of naproxen anti-inflammatory activity during the acute stage of injury could not be determined because of carrageenan failure to elicit swelling. During the subacute stage, naproxen anti-inflammatory effect on forelimbs (above injury) was similar to that observed in sham-injured animals, while it was almost absent in paralyzed hindlimbs. Under conditions of SCI and peripheral inflammation, pharmacokinetics and anti-inflammatory activity of naproxen vary according to post-injury timing and neurological status of the assessed region.

Inhibition of MALT1 paracaspase activity improves lesion recovery following spinal cord injury

Spinal cord injury (SCI) is a devastating traumatic injury that causes persistent, severe motor and sensory dysfunction. Immune responses are involved in functional recovery after SCI. Mucosa-associated lymphoid tissue lymphoma translocation 1 (MALT1) has been shown to regulate the survival and differentiation of immune cells and to play a critical role in many diseases, but its function in lesion recovery after SCI remains unclear. In this paper, we generated KI (knock in) mice with a point mutation (C472G) in the active center of MALT1 and found that the KI mice exhibited improved functional recovery after SCI. Fewer macrophages were recruited to the injury site in KI mice and these macrophages differentiated into anti-inflammatory macrophages. Moreover, macrophages from KI mice exhibited reduced phosphorylation of p65, which in turn resulted in decreased SOCS3 expression and increased pSTAT6 levels. Similar results were obtained upon inhibition of MALT1 paracaspase with the small molecule inhibitor "MI-2" or the more specific inhibitor "MLT-827". In patients with SCI, peripheral blood mononuclear cells (PBMC) displayed increased MALT1 paracaspase. Human macrophages showed reduced pro-inflammatory and increased anti-inflammatory characteristics following the inhibition of MALT1 paracaspase. These findings suggest that inhibition of MALT1 paracaspase activity in the clinic may improve lesion recovery in subjects with SCI.

Salidroside promotes rat spinal cord injury recovery by inhibiting inflammatory cytokine expression and NF-κB and MAPK signaling pathways

Spinal cord injury (SCI) is a public health problem in the world. The SCI usually triggers an excessive inflammatory response that brings about a secondary tissue wreck leading to further cellular and organ dysfunction. Hence, there is great potential of reducing inflammation for therapeutic strategies of SCI. In this study, we aim to investigate if Salidroside (SAD) exerts an anti-inflammatory effect and promotes recovery of motor function on SCI through suppressing nuclear factor-κB (NF-κB) and the mitogen-activated protein kinase (MAPK) pathways. In vitro, real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) were used to examine the inhibitory effect of SAD on the expression and release of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) activated by lipopolysaccharide (LPS) in astrocytes. In addition, SAD was found to inhibit NF-κB, p38 and extracellular-regulated protein kinases (ERK) signaling pathways by western blot analysis. Further, in vivo study showed that SAD was able to improve hind limb motor function and reduce tissue damage accompanied by the suppressed expression of inflammatory cytokines IL-1β, IL-6, and TNF-α. Overall, SAD could reduce the inflammatory response and promote motor function recovery in rats after SCI by inhibiting NF-κB, p38, and ERK signaling pathways.

Early Systemic Alterations in Severe Spinal Cord Injury: An Experimental Study on the Impact of Injury Level on Renal Function

STUDY DESIGN

An experimental model of spinal cord injury (SCI) intended to characterize changes in renal function.

OBJECTIVE

The aim of this study was to evaluate the possible influence of SCI level on renal function during spinal shock.

SUMMARY OF BACKGROUND DATA

SCI triggers multiple systemic and metabolic alterations. Among them, renal dysfunction stands out. Although several variables have been related to its extent, the impact of the cord injury level on renal function has not been clearly stated, particularly during the spinal shock.

METHODS

Anesthetized adult Sprague-Dawley rats were subjected to severe spinal cord contusion at low (T8) and high (T1) thoracic levels using the weight-drop method. Glomerular filtration rate (GFR) and tubular secretion (TS) were estimated 24 hours after injury, using a validated method based on the determination of plasma concentrations of iopamidol and p-aminohippuric acid by high-performance liquid chromatography.

RESULTS

GFR, fell to 33% (95% CI [24%, 43%]) and 10% (8%, 13%) of the sham-injured controls, whereas TS, decreased to 59% (95% CI [47%, 71%]), and 25% (18%, 32%) of the sham-injured controls, in T8 and T1 injury levels, respectively. Comparisons between cords injured and control rats, as well as between low and high-injured levels, were statistically significant (P < 0.01).

CONCLUSION

Renal dysfunction occurs early after severe SCI. The damage is greater in high compared to low injuries. These findings could have important implications in the acute management of patients with high thoracic and cervical injuries, especially in pharmacotherapy using drugs eliminated by the kidney.

LEVEL OF EVIDENCE

N/A.

Time-dependent changes in paw carrageenan-induced inflammation above and below the level of low thoracic spinal cord injury in rats

STUDY DESIGN

This was an animal study.

OBJECTIVES

Local inflammation is attenuated below high thoracic SCI, where innervation of major lymphoid organs is involved. However, whether inflammatory responses are affected after low thoracic SCI, remains undetermined. The aim of this study was to characterize the influence of low thoracic SCI on carrageenan-induced paw swelling in intact and paralyzed limbs, at acute and subacute stages.

SETTING

University and hospital-based research center, Mexico City, Mexico.

METHODS

Rats received a severe contusive SCI at T9 spinal level or sham injury. Then, 1 and 15 days after lesion, carrageenan or vehicle was subcutaneously injected in forelimb and hindlimb paws. Paw swelling was measured over a 6-h period using a plethysmometer.

RESULTS

Swelling increased progressively reaching the maximum 6 h post-carrageenan injection. Swelling increase in sham-injured rats was approximately 130% and 70% compared with baseline values of forelimbs and hindlimbs, respectively. Paws injected with saline exhibited no measurable swelling. Carrageenan-induced paw swelling 1-day post-SCI was suppressed in both intact and paralyzed limbs. Fifteen days post-injury, the swelling response to carrageenan was completely reestablished in forelimbs, whereas in hindlimbs it remained significantly attenuated compared with sham-injured rats.

CONCLUSIONS

SCI at low spinal level affects the induced swelling response in a different way depending on both, the neurological status of challenged regions and the stage of injury. These findings suggest that neurological compromise of the main immunological organs is not a prerequisite for the local swelling response to be affected after injury.

Biomaterials for revascularization and immunomodulation after spinal cord injury

Spinal cord injury (SCI) causes immediate damage to the nervous tissue accompanied by loss of motor and sensory function. The limited self-repair competence of injured nervous tissue underscores the need for reparative interventions to recover function after SCI. The vasculature of the spinal cord plays a crucial role in SCI and repair. Ruptured and sheared blood vessels in the injury epicenter and blood vessels with a breached blood-spinal cord barrier (BSCB) in the surrounding tissue cause bleeding and inflammation, which contribute to the overall tissue damage. The insufficient formation of new functional vasculature in and near the injury impedes endogenous tissue repair and limits the prospect of repair approaches. Limiting the loss of blood vessels, stabilizing the BSCB, and promoting the formation of new blood vessels are therapeutic targets for spinal cord repair. Inflammation is an integral part of injury-mediated vascular damage, which has deleterious and reparative consequences. Inflammation and the formation of new blood vessels are intricately interwoven. Biomaterials can be effectively used for promoting and guiding blood vessel formation or modulating the inflammatory response after SCI, thereby governing the extent of damage and the success of reparative interventions. This review deals with the vasculature after SCI, the reciprocal interactions between inflammation and blood vessel formation, and the potential of biomaterials to support revascularization and immunomodulation in damaged spinal cord nervous tissue.

An Agonist of the Protective Factor SIRT1 Improves Functional Recovery and Promotes Neuronal Survival by Attenuating Inflammation after Spinal Cord Injury

Targeting posttraumatic inflammation is crucial for improving locomotor function. SIRT1 has been shown to play a critical role in disease processes such as hepatic inflammation, rheumatoid arthritis, and acute lung inflammation by regulating inflammation. However, the role of SIRT1 in spinal cord injury (SCI) is unknown. We hypothesized that SIRT1 plays an important role in improving locomotor function after SCI by regulating neuroinflammation. In this study, we investigate the effect of SIRT1 in SCI using pharmacological intervention (SRT1720) and the Mx1-Cre/loxP recombination system to knock out target genes. First, we found that SIRT1 expression at the injured lesion site of wild-type (WT) mice (C57BL/6) decreased 4 h after SCI and lasted for 3 d. Moreover, administration of SRT1720, an agonist of SIRT1, to WT mice significantly improved functional recovery for up to 28 d after injury by reducing the levels of proinflammatory cytokines, the number of M1 macrophages, the number of macrophages/microglia, and the accumulation of perivascular macrophages. In contrast, administration of SRT1720 to SIRT1 knock-out (KO) mice did not improve locomotor recovery or attenuate inflammation. Furthermore, SIRT1 KO mice exhibited worse locomotor recovery, increased levels of inflammatory cytokines, and more M1 macrophages and perivascular macrophages than those of WT mice after SCI. Together, these findings indicate that SRT1720, an SIRT1 agonist, can improve functional recovery by attenuating inflammation after SCI. Therefore, SIRT1 is not only a protective factor but also an anti-inflammatory molecule that exerts beneficial effects on locomotor function after SCI.SIGNIFICANCE STATEMENT Posttraumatic inflammation plays a central role in regulating the pathogenesis of spinal cord injury (SCI). Here, new data show that administration of SRT1720, an SIRT1 agonist, to wild-type (WT) mice significantly improved outcomes after SCI, most likely by reducing the levels of inflammatory cytokines, the number of macrophages/microglia, perivascular macrophages, and M1 macrophages. In contrast, SIRT1 KO mice exhibited worse locomotor recovery than that of WT mice due to aggravated inflammation. Taken together, the results of this study expand upon the previous understanding of the functions and mechanisms of SIRT1 in neuroinflammation following injury to the CNS, suggesting that SIRT1 plays a critical role in regulating neuroinflammation following CNS injury and may be a novel therapeutic target for post-SCI intervention.

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.

Changes in renal function during acute spinal cord injury: implications for pharmacotherapy

STUDY DESIGN

Laboratory investigation in rats submitted to experimental spinal cord injury (SCI).

OBJECTIVE

To characterize changes in renal function during acute SCI.

METHODS

Sprague Dawley rats were subjected to severe spinal cord contusion at T8 level or to laminectomy as control. Twenty-four hours after spine surgery, clearance assessments of a single dose of iohexol (120 mg kg(-1)) or of p-aminohippuric acid (PAH, 100 mg kg(-1)) were used to evaluate glomerular filtration rate (GFR) and tubular secretion (TS), respectively. Blood sampling was used to determine concentrations of both compounds by high-performance liquid chromatography for pharmacokinetic measurements.

RESULTS

Iohexol clearance decreased significantly after injury, which resulted in increased concentrations and half-life of iohexol in blood; PAH clearance remained unchanged.

CONCLUSION

GFR but not TS is altered during spinal shock. These observations should be of interest to professionals caring for early cord-injured patients, in order to prevent toxicity and therapeutic failure when administering drugs eliminated by the kidney.

Pharmacology of riluzole in acute spinal cord injury

OBJECT

The aim of this paper was to characterize individual and population pharmacokinetics of enterally administered riluzole in a Phase 1 clinical trial of riluzole as a neuroprotective agent in adults 18-70 years old with acute spinal cord injury (SCI).

METHODS

Thirty-five individuals with acute SCI, American Spinal Injury Association Impairment Scale Grades A-C, neurological levels from C-4 to T-12, who were enrolled in the Phase 1 clinical trial sponsored by the North American Clinical Trials Network for Treatment of Spinal Cord Injury, received 50 mg riluzole twice daily for 28 doses. The first dose was administered at a mean of 8.7 ± 2.2 hours postinjury. Trough plasma samples were collected within 1 hour predose, and peak plasma samples were collected 2 hours postdose on Days 3 and 14 of treatment. Riluzole concentrations were quantified by high-performance liquid chromatography assay. The data were analyzed for individual and population pharmacokinetics using basic structural and covariate models. The pharmacokinetic measures studied were the peak concentration (C(max)), trough concentration (C(min)), systemic exposure (AUC(0-12)), clearance (CL/F), and volume of distribution (V_F) normalized by the bioavailability (F).

RESULTS

The C(max) and AUC(0-12) achieved in SCI patients were lower than those in ALS patients on the same dose basis, due to a higher CL and larger V. The pharmacokinetics of riluzole (C(max), C(min), AUC(0-12), CL, and V) changed during the acute and subacute phases of SCI during the 14 days of therapy. It was consistently observed in patients at all clinical sites that C(max), C(min), and AUC(0-12) (128.9 ng/ml, 45.6 ng/ml, and 982.0 ng × hr/ml, respectively) were significantly higher on Day 3 than on Day 14 (76.5 ng/ml, 19.1 ng/ml, and 521.0 ng × hr/ml, respectively). These changes resulted from lower CL (49.5 vs 106.2 L/hour) and smaller V (557.1 vs 1297.9/L) on Day 3. No fluid imbalance or cytochrome P 1A2 induction due to concomitant medications was identified during the treatment course to account for such increases in V and CL, respectively. Possible mechanisms underlying these changes are discussed.

CONCLUSIONS

This is the first report of clinical pharmacokinetics of riluzole in patients with SCI. The C(max) and AUC(0-12) achieved in SCI patients were lower than those in ALS patients on the same dose basis, due to a higher clearance and larger volume of distribution in SCI patients. The finding in SCI patients of an increase in the clearance and distribution of riluzole between the 3rd and 14th days after SCI, with a lower plasma concentration of riluzole on the 14th day, stresses the importance of monitoring changes in drug metabolism after SCI in interpreting the safety and efficacy of therapeutic drugs that are used in clinical trials in SCI. Clinical trial registration no.: NCT00876889.

Acute spinal cord injury induces genetic damage in multiple organs of rats

Spinal cord injury (SCI) is a devastating condition with important functional and psychological consequences. However, the underlying mechanisms by which these alterations occur are still not fully understood. The aim of this study was to analyze genomic instability in multiple organs in the acute phase of SCI by means of single cell gel (comet) assay. Rats were randomly distributed into two groups (n = 5): a SHAM and a SCI group killed 24 h after cord transection surgery. The results pointed out genetic damage in blood cells as depicted by the tail moment results. DNA breakage was also detected in liver and kidney cells after SCI. Taken together, our results suggest that SCI induces genomic damage in multiple organs of Wistar rats.

Molecular and cellular mechanisms underlying the role of blood vessels in spinal cord injury and repair

Spinal cord injury causes immediate damage of nervous tissue accompanied by the loss of motor and sensory function. The limited self-repair ability of damaged nervous tissue underlies the need for reparative interventions to restore function after spinal cord injury. Blood vessels play a crucial role in spinal cord injury and repair. Injury-induced loss of local blood vessels and a compromised blood-brain barrier contribute to inflammation and ischemia and thus to the overall damage to the nervous tissue of the spinal cord. Lack of vasculature and leaking blood vessels impede endogenous tissue repair and limit prospective repair approaches. A reduction of blood vessel loss and the restoration of blood vessels so that they no longer leak might support recovery from spinal cord injury. The promotion of new blood vessel formation (i.e., angio- and vasculogenesis) might aid repair but also incorporates the danger of exacerbating tissue loss and thus functional impairment. The delicate interplay between cells and molecules that govern blood vessel repair and formation determines the extent of damage and the success of reparative interventions. This review deals with the cellular and molecular mechanisms underlying the role of blood vessels in spinal cord injury and repair.

Severity of locomotor and cardiovascular derangements after experimental high-thoracic spinal cord injury is anesthesia dependent in rats

Anesthetics affect outcomes from central nervous system (CNS) injuries differently. This is the first study to show how two commonly used anesthetics affect continuously recorded hemodynamic parameters and locomotor recovery during a 2-week period after two levels of contusion spinal cord injury (SCI) in rats. We hypothesized that the level of cardiovascular depression and recovery of locomotor function would be dependent upon the anesthetic used during SCI. Thirty-two adult female rats were subjected to a sham, 25-mm or 50-mm SCI at T3-4 under pentobarbital or isoflurane anesthesia. Mean arterial pressure (MAP) and heart rate (HR) were telemetrically recorded before, during, and after SCI. Locomotor function recovered best in the 25-mm-injured isoflurane-anesthetized animals. There was no significant difference in locomotor recovery between the 25-mm-injured pentobarbital-anesthetized animals and the 50-mm-injured isoflurane-anesthetized animals. White matter sparing and extent of intermediolateral cell column loss appeared larger in animals anesthetized with pentobarbital, but this was not significant. There were no differential effects of anesthetics on HR and MAP before SCI, but recovery from anesthesia was significantly slower in pentobarbital-anesthetized animals. At the time of SCI, MAP was acutely elevated in the pentobarbital-anesthetized animals, whereas MAP decreased in the isoflurane-anesthetized animals. Hypotension occurred in the pentobarbital-anesthetized groups and in the 50-mm-injured isoflurane-anesthetized group. In pentobarbital-anesthetized animals, SCI resulted in acute elevation of HR, although HR remained low. Return of HR to baseline was much slower in the pentobarbital-anesthetized animals. Severe SCI at T3 produced significant chronic tachycardia that was injury severity dependent. Although some laboratories monitor blood pressure, HR, and other physiological variables during surgery for SCI, inherently few have monitored cardiovascular function during recovery. This study shows that anesthetics affect hemodynamic parameters differently, which in turn can affect functional outcome measures. This supports the need for a careful evaluation of cardiovascular and other physiological measures in experimental models of SCI. Choice of anesthetic should be an important consideration in experimental designs and data analyses.

Assessment of hepatic inflammation after spinal cord injury using intravital microscopy

OBJECTIVES

The liver has been shown to play a particularly important role in the initiation and progression of the early systemic inflammatory response (SIR) to spinal cord injury (SCI). The purpose of this study was to determine the time course of leucocyte recruitment to the liver, and to determine the effect of injury severity on the magnitude of leucocyte recruitment and hepatic injury.

METHODS

Rats were randomly assigned to one of the following groups: uninjured, sham-injured (laminectomy and no cord injury), cord compressed or cord transected. At 30 min and 90 min after SCI rats had the left lobe of their livers externalised and visualised using intravital video microscopy.

RESULTS

Thirty minutes after injury the total number of leucocytes per post-sinusoidal venule was significantly increased after cord transection compared to that in uninjured and sham-injured rats (P<0.05). Of these leucocytes, significantly more were adherent to venule walls (P<0.05). At 90 min the total number of leucocytes per post-sinusoidal venule and the number of adherent and rolling leucocytes was significantly increased after cord transection and cord compression (P<0.05).

DISCUSSION

This is the first study to use intravital microscopy to visualise systemic inflammation in the liver following SCI. We have demonstrated immediate leucocyte recruitment to the liver within 30 min after injury and have shown that systemic inflammation increases with time after injury and with severity of injury.

Spinal cord injury sequelae alter drug pharmacokinetics: an overview

STUDY DESIGN

Literature review.

OBJECTIVES

Critical review of the literature published on the physiological alterations caused by spinal cord injury (SCI) and their effect on the pharmacokinetic parameters of commonly employed drugs. The review introduces the most recent treatment protocols of a variety of drugs, enabling the modern clinician to apply efficacious and cost-effective solutions to the pharmacological treatment of SCI patients.

METHODS

Studies published in international indexed journals up to January 2011 were selected from the PubMed database.

RESULTS

The review evaluated the sequelae of SCI and their effect on pharmacological processes. The results demonstrated that these alterations affected the pharmacokinetics of drugs commonly administered to SCI patients, such as antibiotics, muscle relaxants, immunosuppressants and analgesics.

CONCLUSION

There are multiple etiologies to SCI and patients present with varying degrees of impairment. Factors such as level of injury and completeness of the injury create a very heterogeneous population within the SCI community. The heterogeneity of this population creates a problem when trying to standardize pharmacokinetic (PK) parameters. It is because of this that specific physiological alterations must be linked to changes in PK and be identified within the clinical setting. This relationship between physiology and PK enables the clinician to be alert for possible pharmacological complications in individual patients based on their clinical manifestations. Future research should aim to develop rigorous therapeutic guidelines tailored to the diverse manifestations of SCI so as to provide effective, affordable and safe pharmacotherapy.

Potential adverse effects of cyclosporin A on kidneys after spinal cord injury

STUDY DESIGN

Cell transplantation strategies are gaining increasing interest for spinal cord injury (SCI) with the objective of promoting spinal cord repair. To avoid allogenic graft rejection, an adequate immune suppression is required, and one of the most potent and commonly used immunosuppressives is cyclosporin A (CsA). In SCI, permanent sensory motor loss is combined with modifications of drug absorption, distribution and elimination.

OBJECTIVES

The objectives of this study were to thoroughly explore histological and functional outcomes of CsA treatment in a rat model of spinal cord compression.

SETTING

Experiments were carried out at the Institute for Neurosciences of Montpellier (France), the Integrative Biology of Neurodegeneration Laboratory (Spain) and in the Novartis Institutes for BioMedical Research (Switzerland) for CsA blood concentration determination.

METHODS

We first evaluated histological outcomes of CsA treatment on kidneys and spinal cord after SCI. We then investigated whether SCI modified CsA blood concentration. Finally, using behavioral analysis, we assessed the potential CsA impact on functional recovery.

RESULTS

When spinal-cord-injured rats were treated with a CsA dose of 10 mg kg(-1) per day, we observed deleterious effects on kidneys, associated with modifications of CsA blood concentration. Adding an antibiotic treatment reduced kidney alteration without modifying CsA blood concentration. Finally, we showed that CsA treatment per se modified neither functional recovery nor lesion extension.

CONCLUSION

This study pinpoints the absolute requirement of careful CsA monitoring in the clinical setting for patients with SCI to minimize potential unexpected effects and avoid therapeutic failure.

Infarction of middle third posterior cortex of kidney: a complication of extended pyelolithotomy, intra-operative electrohydraulic lithotripsy and extraction of calyceal stones under vision using stone basket and flexible cystoscope in a spinal cord injury patient - a case report

BACKGROUND

Spinal cord injury produces multiple systemic and metabolic alterations. A decrease in micro vascular blood flow to liver, spleen and muscle has been described following spinal cord injury.

CASE PRESENTATION

We present a 46-year-old male patient with C-4 complete tetraplegia, who developed a large stag horn calculus with branches in upper, middle and lower calyces of left kidney. This patient underwent Gil-Vernet extended pyelolithotomy and required intra-operative electrohydraulic lithotripsy and retrieval of stones from upper, middle and lower calyces using flexible cystoscope and stone basket. Computed tomography, performed eighteen days after surgery, showed multiple areas of non-enhancing cortex posteriorly and in the upper pole, suggestive of focal infarction. Magnetic resonance imaging of left kidney confirmed the presence of an area of infarction in middle third of posterior cortex, but there was no evidence of trauma to posterior division of renal artery. Therefore, we postulate that compression of renal parenchyma by Gil-Vernet retractors during surgery, and firm pressure that was applied over the middle of kidney for prolonged periods while several attempts were being made to retrieve fragments of calculi from renal calyces, led to ischaemia and subsequently, infarction of mid-third posterior cortex of left kidney.

CONCLUSION

This case illustrates importance of gentle handling of kidney during extended pyelolithotomy in order to prevent subtle renal trauma, which may be detected only by advanced imaging studies. Further, spinal cord physicians should take a pragmatic approach to management of stones located inside renal calyces. Both spinal cord injury patients and their physicians should remember that in our enthusiasm to achieve complete clearance of stones embedded deeply within renal calyces, we could produce irreversible injury to kidney, as indeed happened in this patient. Therefore, emphasis should be placed on prevention of struvite renal calculi by discarding indwelling urinary catheters and eliminating Proteus bacteriuria.

Acute, subacute and chronic effect of cyclosporin-A on mean arterial pressure of rats with severe spinal cord contusion

Cyclosporin-A (CsA) protects and regenerates the neural tissue after spinal cord (SC) injury. These beneficial effects are achieved when CsA is administered at a dose of 2.5mg/kg/12h during the first 2 days after lesion. In view of these observations, it is realistic to envision that, CsA could be tested in SC-clinical trials. Since CsA is a drug strongly related to hypertension, results imperative to evaluate experimentally the effect of the above CsA-dose regimen on blood pressure. For this purpose, one hundred and twenty adult rats were subjected (10 groups) or not (10 groups) to SC-injury. Five injured and five Sham-operated groups received CsA. The remaining groups received only vehicle. Mean arterial pressure (MAP) was recorded from these animals at acute (6 and 24h post surgery; p.s.), subacute (96h), or chronic (30 days) stages of injury. In the latter, the therapy (CsA or vehicle) was administered only during the first 2 days p.s. or daily during 30 days of follow-up. The results of this study showed that SC-injury by itself induces a significant decrease of MAP during the acute and subacute phases of injury. CsA therapy was able to reestablish MAP parameters to control values in these phases. Regardless the therapy, a reestablishment of MAP was observed in chronic stages. Only the daily administration of CsA induced a significant increase in MAP, however; such variation remained into the normal ranges of MAP for rats. The potential benefits offered by CsA support its usefulness after SC-injury.

L-arginine reverses alterations in drug disposition induced by spinal cord injury by increasing hepatic blood flow

High hepatic extraction drugs--such as phenacetin, methylprednisolone, and cyclosporine--exhibit an increased bioavailability after acute spinal cord injury (SCI) due to an impaired clearance. For these drugs, metabolic clearance depends on hepatic blood flow. Thus, it is possible that pharmacokinetic alterations can be reversed by increasing liver perfusion. Therefore, we evaluated the effect of L-arginine, a nitric oxide precursor, on the pharmacokinetics of a prototype drug with high hepatic extraction, and on hepatic microvascular blood flow (MVBF) after acute SCI. Pharmacokinetics of i.v. phenacetin was studied in rats 24 h after a severe T-5 spinal cord contusion; animals being pretreated with L-arginine 100 mg/kg i.v. or vehicle. MVBF was assessed under similar experimental conditions using laser Doppler flowmetry. SCI significantly altered phenacetin pharmacokinetics. Clearance was significantly reduced, resulting in a prolonged half-life and an increase in bioavailability, while volume of distribution was decreased. Pharmacokinetic alterations were reversed when injured rats were pretreated with L -arginine. It was also observed that L-arginine significantly increased hepatic MVBF in injured rats, notwithstanding it exhibited a limited effect on sham-injured animals. Our data hence suggest that L-arginine is able to reverse SCI-induced alterations in phenacetin pharmacokinetics due to an impaired hepatic MVBF, likely by increased nitric oxide synthesis leading to vasodilation. Further studies are warranted to examine the potential usefulness of nitric oxide supplementation in a clinical setting.

Hormonal and immunological changes in mice after spinal cord injury

Spinal cord injury (SCI) is associated with immune deficiencies and life-threatening infections. However, the specific mechanisms underlying this pathological condition remain unclear. In recent years, increasing evidence has suggested that anabolic hormones may be involved in immunological complications. Here, we monitored candidate hormone concentrations and immune cell counts, in CD1 mice, for 4 weeks after low-thoracic transection of the spinal cord (Tx). Serum dihydroepiandrosterone (DHEA), insulin, and parathyroid hormone (PTH) levels decreased throughout the time period studied compared with control, non-Tx mice. In turn, testosterone and growth hormone (GH) levels were only transiently changed, with a decrease of testosterone during the first 2 weeks and an increase of GH at 1 week post-Tx. A complete blood count revealed either unchanged or moderately decreased erythrocyte, platelet, hemoglobin and hematocrit levels. Total leukocyte, lymphocyte, and eosinophil counts also decreased, whereas neutrophils and monocytes did not change significantly. In the bone marrow, lymphocyte numbers decreased and neutrophils increased, whereas monocytes, eosinophils, and megakariocytes did not change significantly. These results revealed significant changes occurring rapidly (<1-2 weeks) after Tx in both hormonal and immunological systems, providing compelling evidence of a role for anabolic hormones in SCI-related immune deficiencies.

Restoring function after spinal cord injury: promoting spontaneous regeneration with stem cells and activity-based therapies

Although neural regeneration is an active research field today, no current treatments can aid regeneration after spinal cord injury. This article reviews the feasibility of spinal cord repair and provides an overview of the range of strategies scientists are taking toward regeneration. The major focus of this article is the future role of stem cell transplantation and similar rehabilitative restorative approaches designed to optimize spontaneous regeneration by mobilizing endogenous stem cells and facilitating other cellular mechanisms of regeneration, such as axonal growth and myelination.

Acute spinal cord injury changes the disposition of some, but not all drugs given intravenously

STUDY DESIGN

Experimental laboratory investigations in paraplegic rats.

OBJECTIVE

In order to understand why acute spinal cord injury (SCI) changes the disposition of some, but not all drugs given intravenously (i.v.), pharmacokinetic parameters of drugs with different pharmacological properties were evaluated to determine the influence of SCI on physiological processes such as distribution, metabolism and excretion.

SETTING

Mexico City, Mexico.

METHODS

Rats were subjected to severe SCI (contusion) at T-9 level; pharmacokinetic studies of phenacetin, naproxen or gentamicin were performed 24 h after. These drugs were not chosen as markers because of their therapeutic properties, but because of their pharmacokinetic characteristics. Additional studies including plasma proteins, liver and renal function tests, and micro-vascular hepatic blood flow, were also performed at the same time after injury.

RESULTS

Acute SCI significantly reduced distribution of drugs with intermediate and low binding to plasma proteins (phenacetin 30% and gentamicin 10%, respectively), but distribution did not change when naproxen - a drug highly bound to plasma proteins (99%) - was used, in absence of changes in plasma proteins. Metabolism was significantly altered only for a drug with liver blood flow - limited clearance (phenacetin) and not for a drug with liver capacity-limited clearance (naproxen). The liver function test did not change, whereas the hepatic micro-vascular blood flow significantly decreased after SCI. Renal excretion, evaluated by gentamicin clearance, was significantly reduced as a consequence of SCI, without significant changes in serum creatinine.

CONCLUSIONS

Changes in drug disposition associated to acute SCI are complex and generalization is not possible. They are highly dependent on each drug properties as well as on the altered physiological processes. Results motivate the quest for strategies to improve disposition of selective i.v. drugs during spinal shock, in an effort to avoid therapeutic failure.

Degenerative and spontaneous regenerative processes after spinal cord injury

Spinal cord injury results in acute as well as progressive secondary destruction of local and distant nervous tissue through a number of degenerative mechanisms. Spinal cord injury also initiates a number of endogenous neuroprotective and regenerative responses. Understanding of these mechanisms might identify potential targets for treatments after spinal cord injury in humans. Here, we first discuss recent developments in our understanding of the immediate traumatic and subsequent secondary degeneration of local tissue and long projecting pathways in animal models. These include the inflammatory and vascular responses during the acute phase, as well as cell death, demyelination and scar formation in the subacute and chronic phases. Secondly, we discuss the spontaneous axonal regeneration of injured and plasticity of uninjured systems, and other repair-related responses in animals, including the upregulation of regeneration-associated genes in some neurons, increases in neurotrophic factors in the spinal cord and remyelination by oligodendrocyte precursors and invading Schwann cells. Lastly, we comment on the still limited understanding of the neuropathology in humans, which is largely similar to that in rodents. However, there also are potentially important differences, including the reduced glial scarring, inflammation and demyelination, the increased Schwannosis and the protracted Wallerian degeneration in humans. The validity of current rodent models for human spinal cord injury is also discussed. The emphasis of this review is on the literature from 2002 to early 2005.

Understanding Drug Disposition Alterations Induced by Acute Spinal Cord Injury: Role of Injury Level and Route of Administration for Agents Submitted to Extensive Liver Metabolism

It is known that acute spinal cord injury (SCI) produces hemodynamic alterations, including a reduction in liver blood flow that is more pronounced after high-thoracic than after low-thoracic injury. To determine if these changes have an impact in the pharmacokinetics of high extraction drugs (i.e., those drugs which clearance mainly depends on liver blood flow), we studied the pharmacokinetics of a model compound, phenacetin, and of its main metabolite, acetaminophen, in rats 24 h after a high (T1) or a low (T8) SCI, as well as in sham-lesioned controls. After intravenous administration to animals with SCI, reductions in drug clearance and distribution led to an increase in blood concentrations. These alterations were more pronounced after high than after low SCI, as expected from hemodynamic changes. After oral administration, phenacetin blood levels were similar in sham-lesioned and T1-injured animals, but decreased by injury at T8. This is likely due to a reduction in drug absorption which compensates the changes in distribution and elimination induced by injury at T1, whereas it prevails in T8-lesioned animals. Acetaminophen blood concentrations observed after intravenous or oral phenacetin, or after the oral administration of acetaminophen by itself, were increased or reduced, depending on the overall effect of the alterations on absorption, first pass metabolism, distribution and elimination induced by high and low SCI. Results demonstrate that acute SCI significantly alters the pharmacokinetics of high extraction drugs. The outcome of such alterations depends on the level of SCI and on the route of administration.