Assessment of hepatic inflammation after spinal cord injury using intravital microscopy

Consequences of spinal cord injury on the sympathetic nervous system

Spinal cord injury (SCI) damages multiple structures at the lesion site, including ascending, descending, and propriospinal axons; interrupting the conduction of information up and down the spinal cord. Additionally, axons associated with the autonomic nervous system that control involuntary physiological functions course through the spinal cord. Moreover, sympathetic, and parasympathetic preganglionic neurons reside in the spinal cord. Thus, depending on the level of an SCI, autonomic function can be greatly impacted by the trauma resulting in dysfunction of various organs. For example, SCI can lead to dysregulation of a variety of organs, such as the pineal gland, the heart and vasculature, lungs, spleen, kidneys, and bladder. Indeed, it is becoming more apparent that many disorders that negatively affect quality-of-life for SCI individuals have a basis in dysregulation of the sympathetic nervous system. Here, we will review how SCI impacts the sympathetic nervous system and how that negatively impacts target organs that receive sympathetic innervation. A deeper understanding of this may offer potential therapeutic insight into how to improve health and quality-of-life for those living with SCI.

Baseline predictors of in-hospital mortality after acute traumatic spinal cord injury: data from a level I trauma center

Comorbidity scores are important predictors of in-hospital mortality after traumatic spinal cord injury (tSCI), but the impact of specific pre-existing diseases is unknown. This retrospective cohort study aims at identifying relevant comorbidities and explores the influence of end-of-life decisions. In-hospital mortality of all patients admitted to the study center after acute tSCI from 2011 to 2017 was assessed. A conditional inference tree analysis including baseline data, injury characteristics, and Charlson Comorbidity Index items was used to identify crucial predictors. End-of-life decisions were recorded. Three-hundred-twenty-one patients were consecutively enrolled. The median length of stay was 95.7 days (IQR 56.8-156.0). During inpatient care, 20 patients (6.2%) died. These patients were older (median: 79.0 (IQR 74.7-83.2) vs. 55.5 (IQR 41.4-72.3) years) and had a higher Charlson Comorbidity Index score (median: 4.0 (IQR 1.75-5.50) vs. 0.0 (IQR 0.00-1.00)) compared to survivors. Pre-existing kidney or liver disease were identified as relevant predictors of in-hospital mortality. End-of-life decisions were observed in 14 (70.0%) cases. The identified impairment of kidney and liver, important for drug metabolism and elimination, points to the need of careful decisions on pharmaceutical treatment regimens after tSCI. Appropriate reporting of end-of-life decisions is required for upcoming studies.

Evaluation of the Cardiometabolic Disorders after Spinal Cord Injury in Mice

Changes in cardiometabolic functions contribute to increased morbidity and mortality after chronic spinal cord injury. Despite many advancements in discovering SCI-induced pathologies, the cardiometabolic risks and divergences in severity-related responses have yet to be elucidated. Here, we examined the effects of SCI severity on functional recovery and cardiometabolic functions following moderate (50 kdyn) and severe (75 kdyn) contusions in the thoracic-8 (T8) vertebrae in mice using imaging, morphometric, and molecular analyses. Both severities reduced hindlimbs motor functions, body weight (g), and total body fat (%) at all-time points up to 20 weeks post-injury (PI), while only severe SCI reduced the total body lean (%). Severe SCI increased liver echogenicity starting from 12 weeks PI, with an increase in liver fibrosis in both moderate and severe SCI. Severe SCI mice showed a significant reduction in left ventricular internal diameters and LV volume at 20 weeks PI, associated with increased LV ejection fraction as well as cardiac fibrosis. These cardiometabolic dysfunctions were accompanied by changes in the inflammation profile, varying with the severity of the injury, but not in the lipid profile nor cardiac or hepatic tyrosine hydroxylase innervation changes, suggesting that systemic inflammation may be involved in these SCI-induced health complications.

Hepatic Nervous System in Development, Regeneration, and Disease

The liver is innervated by autonomic and sensory fibers of the sympathetic and parasympathetic nervous systems that regulate liver function, regeneration, and disease. Although the importance of the hepatic nervous system in maintaining and restoring liver homeostasis is increasingly appreciated, much remains unknown about the specific mechanisms by which hepatic nerves both influence and are influenced by liver diseases. While recent work has begun to illuminate the developmental mechanisms underlying recruitment of nerves to the liver, evolutionary differences contributing to species-specific patterns of hepatic innervation remain elusive. In this review, we summarize current knowledge on the development of the hepatic nervous system and its role in liver regeneration and disease. We also highlight areas in which further investigation would greatly enhance our understanding of the evolution and function of liver innervation.

Hepatic dysfunction after spinal cord injury: A vicious cycle of central and peripheral pathology?

The liver is essential for numerous physiological processes, including filtering blood from the intestines, metabolizing fats, proteins, carbohydrates and drugs, and regulating iron storage and release. The liver is also an important immune organ and plays a critical role in response to infection and injury throughout the body. Liver functions are regulated by autonomic parasympathetic innervation from the brainstem and sympathetic innervation from the thoracic spinal cord. Thus, spinal cord injury (SCI) at or above thoracic levels disrupts major regulatory mechanisms for hepatic functions. Work in rodents and humans shows that SCI induces liver pathology, including hepatic inflammation and fat accumulation characteristic of a serious form of non-alcoholic fatty liver disease (NAFLD) called non-alcoholic steatohepatitis (NASH). This hepatic pathology is associated with and likely contributes to indices of metabolic dysfunction often noted in SCI individuals, such as insulin resistance and hyperlipidemia. These occur at greater rates in the SCI population and can negatively impact health and quality of life. In this review, we will: 1) Discuss acute and chronic changes in human and rodent liver pathology and function after SCI; 2) Describe how these hepatic changes affect systemic inflammation, iron regulation and metabolic dysfunction after SCI; 3) Describe how disruption of the hepatic autonomic nervous system may be a key culprit in post-injury chronic liver pathology; and 4) Preview ongoing and future research that aims to elucidate mechanisms driving liver and metabolic dysfunction after SCI.

A Preliminary Cohort Study Assessing Routine Blood Analyte Levels and Neurological Outcome after Spinal Cord Injury

There is increasing interest in the identification of biomarkers that could predict neurological outcome following a spinal cord injury (SCI). Although initial American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade is a good indicator of neurological outcome, for the patient and clinicians, an element of uncertainty remains. This preliminary study aimed to assess the additive potential of routine blood analytes following principal component analysis (PCA) to develop prognostic models for neurological outcome following SCI. Routine blood and clinical data were collected from SCI patients (n = 82) and PCA used to reduce the number of blood analytes into related factors. Outcome neurology was obtained from AIS scores at 3 and 12 months post-injury, with motor (AIS and total including all myotomes) and sensory (AIS, touch and pain) abilities being assessed individually. Multiple regression models were created for all outcome measures. Blood analytes relating to “liver function” and “acute inflammation and liver function” factors were found to significantly increase prediction of neurological outcome at both 3 months (touch, pain, and AIS sensory) and at 1 year (pain, R² increased by 0.025 and total motor, R² increased by 0.016). For some models “liver function” and “acute inflammation and liver function” factors were both significantly predictive, with the greatest combined R² improvement of 0.043 occurring for 3 month pain prediction. These preliminary findings support ongoing research into the use of routine blood analytes in the prediction of neurological outcome in SCI patients.

Activity/exercise-induced changes in the liver transcriptome after chronic spinal cord injury

Multi-organ dysfunction is a major complication after spinal cord injury (SCI). In addition to local injury within the spinal cord, SCI causes major disruption to the peripheral organ innervation and regulation. The liver contains sympathetic, parasympathetic, and small sensory axons. The bi-directional signaling of sensory dorsal root ganglion (DRG) neurons that provide both efferent and afferent information is of key importance as it allows sensory neurons and peripheral organs to affect each other. SCI-induced liver inflammation precedes and may exacerbate intraspinal inflammation and pathology after SCI, which may be modulated by activity and exercise. In this study, we collected comprehensive gene expression data through RNA sequencing of liver tissue from rats with chronic SCI to determine the effects of activity and exercise on those expression patterns. The sequenced data are of high quality and show a high alignment rate to the Rn6 genome. Gene expression is demonstrated for genes associated with known liver pathologies. UCSC Genome Browser expression tracks are provided with the data to facilitate exploration of the samples.

State of the art of management of hepatic myelopathy

Hepatic myelopathy (HM) is characterized by progressive weakness and spasticity of the lower extremities, which is a severe spinal cord involvement rarely occurring in patients with cirrhosis or other chronic liver diseases. The diagnosis is assigned after the exclusion of other clinical entities leading to spastic paraparesis. Liver transplantation represents a potentially treatment for HM in early stage.

Multiple organ dysfunction and systemic inflammation after spinal cord injury: a complex relationship

Spinal cord injury (SCI) is a devastating event that results in significant physical disabilities for affected individuals. Apart from local injury within the spinal cord, SCI patients develop a variety of complications characterized by multiple organ dysfunction or failure. These disorders, such as neurogenic pain, depression, lung injury, cardiovascular disease, liver damage, kidney dysfunction, urinary tract infection, and increased susceptibility to pathogen infection, are common in injured patients, hinder functional recovery, and can even be life threatening. Multiple lines of evidence point to pathological connections emanating from the injured spinal cord, post-injury systemic inflammation, and immune suppression as important multifactorial mechanisms underlying post-SCI complications. SCI triggers systemic inflammatory responses marked by increased circulation of immune cells and pro-inflammatory mediators, which result in the infiltration of inflammatory cells into secondary organs and persistence of an inflammatory microenvironment that contributes to organ dysfunction. SCI also induces immune deficiency through immune organ dysfunction, resulting in impaired responsiveness to pathogen infection. In this review, we summarize current evidence demonstrating the relevance of inflammatory conditions and immune suppression in several complications frequently seen following SCI. In addition, we highlight the potential pathways by which inflammatory and immune cues contribute to multiple organ failure and dysfunction and discuss current anti-inflammatory approaches used to alleviate post-SCI complications. A comprehensive review of this literature may provide new insights into therapeutic strategies against complications after SCI by targeting systemic inflammation.

The systemic response to CNS injury

Inflammation within the brain or spinal cord has the capacity to damage neurons and is known to contribute to long-term disability in a spectrum of central nervous system (CNS) pathologies. However, there is a more profound increase in the recruitment of potentially damaging populations of leukocytes to the spinal cord than to the brain after equivalent injuries. Increased levels of inflammatory cytokines and chemokines in the spinal cord underpin this dissimilarity after injury, which also appears to be very sensitive to processes that operate within organs distant from the primary injury site such as the liver, lung and spleen. Indeed, CNS injury per se can generate profound changes in gene expression and the cellularity of these organs, which, as a consequence, gives rise to secondary organ damage. Our understanding of the local inflammatory processes that can damage neurons is becoming clearer, but our understanding of how the peripheral immune system coordinates the response to CNS injury and how any concomitant infections or injury might impact on the outcome of CNS injury is not so well developed. It is clear that the orientation of the response to peripheral challenges, be it a pro- or anti-inflammatory effect, appears to be dependent on the nature and timing of events. Here, the importance of the inter-relationship between inflammation in the CNS and the consequent inflammatory response in peripheral tissues is highlighted.

Systemic inflammatory response syndrome in patients with spinal cord injury: does its presence at admission affect patient outcomes? Clinical article

OBJECT

The object in this study was to determine whether the presence of systemic inflammatory response syndrome (SIRS) in patients with traumatic spinal cord injury (SCI) on admission is related to subsequent clinical outcome in terms of length of stay (LOS), complications, and mortality.

METHODS

The authors retrospectively reviewed the charts of 193 patients with acute traumatic SCI who had been hospitalized at their institution between 2006 and 2012. Patients were excluded from analysis if they had insufficient SIRS data, a cauda equina injury, a previous SCI, a preexisting neurological condition, or a condition on admission that prevented appropriate neurological assessment. Complications were counted only once per patient and were considered minor if they were severe enough to warrant treatment and major if they were life threatening. Demographics, injury characteristics, and outcomes were compared between individuals who had 2 or more SIRS criteria (SIRS+) and those who had 0 or 1 SIRS criterion (SIRS-) at admission. Multivariate logistic regression (enter method) was used to determine the relative contribution of SIRS+ at admission in predicting the outcomes of mortality, LOS in the intensive care unit (ICU), hospital LOS, and at least one major complication during the acute hospitalization. The American Spinal Injury Association Impairment Scale grade and patient age were included as covariates.

RESULTS

Ninety-three patients were eligible for analysis. At admission 47.3% of patients had 2 or more SIRS criteria. The SIRS+ patients had higher Injury Severity Scores (24.3 ±10.6 vs. 30.2 ±11.3) and a higher frequency of both at least one major complication during acute hospitalization (26.5% vs. 50.0%) and a fracture-dislocation pattern of injury (26.5% vs. 59.1%) than the SIRS- patients (p < 0.05 for each comparison). The SIRS+ patients had a longer median hospital stay (14 vs 18 days) and longer median ICU stay (0 vs. 5 days). However, mortality was not different between the groups. Having SIRS on admission predicted an ICU LOS > 10 days, hospital LOS > 25 days, and at least one complication during the acute hospitalization.

CONCLUSIONS

A protocol to identify SCI patients with SIRS at admission may be beneficial with respect to preventing adverse outcomes and decreasing hospital costs.

Remote inflammatory response in liver is dependent on the segmental level of spinal cord injury

BACKGROUND

Traumatic spinal cord injury (SCI) triggers a systemic inflammatory response (SIR) that contributes to a high incidence of secondary organ complications, particularly after a cervical or high-level thoracic injury. Because liver plays a key role in initiating and propagating the SIR, the aim of this study was to assess the effects that SCI at differing segmental levels has on the intensity of the inflammatory response in the liver.

METHODS

Using male Wistar rats, clip compression SCI was performed at the 4th thoracic (T4 SCI; high-level SCI) or the 12th thoracic (T12 SCI; low-level SCI) spinal cord segment. Sham-injured rats had a partial laminectomy, but no SCI. Leukocyte recruitment to the liver, hepatic blood flow, and hepatocellular injury/death were assessed using intravital microscopy and histology. Chemokine and cytokine concentrations were assessed in the liver. Outcomes were measured at 1.5 hours, 12 hours, and 24 hours after SCI.

RESULTS

At 12 hours after injury, T4 SCI caused a threefold increase in hepatic leukocyte recruitment compared with T12 SCI (p < 0.05). T4 SCI induced 50% more hepatocyte injury than T12 SCI at 12 hours (p < 0.05). Hepatic blood flow decreased after SCI, but not after sham injury, and stayed decreased only after T4 SCI at 24 hours after injury. The T4 SCI-induced changes were accompanied by increases in the hepatic concentrations of interleukin-1β, leptin, interleukin 10, and cytokine-induced neutrophil chemoattractant-1 at 1.5 hours.

CONCLUSIONS

Our findings indicate that traumatic SCI triggers an acute SIR that contributes to hepatocellular injury. SCI-induced remote injury/dysfunction to the liver appears to be transient and is more robust after an upper thoracic SCI compared with a lower thoracic SCI.

The systemic inflammatory response after spinal cord injury in the rat is decreased by α4β1 integrin blockade

Abstract The systemic inflammatory response syndrome (SIRS) follows spinal cord injury (SCI) and causes damage to the lungs, kidney, and liver due to an influx of inflammatory cells from the circulation. After SCI in rats, the SIRS develops within 12 h and is sustained for at least 3 days. We have previously shown that blockade of CD11d/CD18 integrin reduces inflammation-driven secondary damage to the spinal cord. This treatment reduces the SIRS after SCI. In another study we found that blockade of α4β1 integrin limited secondary cord damage more effectively than blockade of CD11d/CD18. Therefore we considered it important to assess the effects of anti-α4β1 treatment on the SIRS in the lung, kidney, and liver after SCI. An anti-α4 antibody was given IV at 2 h after SCI at the fourth thoracic segment and the effects on the organs were evaluated at 24 h post-injury. The migration of neutrophils into the lungs and liver was markedly reduced and all three organs contained fewer macrophages. In the lungs and liver, the activation of the oxidative enzymes myeloperoxidase (MPO), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and gp91(phox), the production of free radicals, lipid peroxidation, and cell death were substantially and similarly reduced. Treatment effects were less robust in the kidney. Overall, the efficacy of the anti-α4β1 treatment did not differ greatly from that of the anti-CD11d antibody, although details of the results differed. The SIRS after SCI impedes recovery, and attenuation of the SIRS with an anti-integrin treatment is an important, clinically-relevant finding.

CD11d integrin blockade reduces the systemic inflammatory response syndrome after spinal cord injury

Traumatic injury to the spinal cord triggers a systemic inflammatory response syndrome (SIRS), in which inflammatory cells from the circulation invade organs such as the liver, lung and kidney, leading to damage of these organs. Our previous study (Gris, et al, Exp. Neurol, 2008) demonstrated that spinal cord injury (SCI) activates circulating neutrophils that then invade the lung and kidney from 2 to 24 h after injury, increasing myeloperoxidase activity, cyclooxygenase-2 and matrix metalloproteinase-9 expression and lipid peroxidation in these organs. The present study was designed to ascertain whether a treatment that limits the influx of leukocytes into the injured spinal cord would also be effective in reducing the SIRS after SCI. This treatment is intravenous delivery of a monoclonal antibody (mAb) against the CD11d subunit of the CD11d/CD18 integrin expressed by neutrophils and monocytes. We delivered the anti-CD11d mAb at 2 h post moderate clip compression SCI at the 4th or 12th thoracic segments and assessed inflammation, oxidative activity and cellular damage within the lung, kidney and liver at 12 h post-injury. In some analyses we compared high and low thoracic injuries to evaluate the importance of injury level on the intensity of the SIRS. After T4 injury, treatment with the anti-integrin mAb reduced the presence of neutrophils and macrophages in the lung, with associated decreases in expression of NF-κB and oxidative enzymes and in the concentration of free radicals in this organ. The treatment also reduced lipid peroxidation, protein nitration and cell death in the lung. The anti-CD11d treatment also reduced the inflammatory cells within the kidney after T4 injury, as well as the free radical concentration and amount of lipid peroxidation. In the liver, the mAb treatment reduced the influx of neutrophils but most of the other measures examined were unaffected by SCI. The inflammatory responses within the lung and kidney were often greater after T4 than T12 injury. Clinical studies show that SIRS, with its associated organ failure, contributes significantly to the morbidity and mortality of SCI patients. This anti-integrin treatment may block the onset of SIRS after SCI.