Arachidonic acid: a bridge between traumatic brain injury and fracture healing

Brain-Bone Crosstalk in a Murine Polytrauma Model Promotes Bone Remodeling but Impairs Neuromotor Recovery and Anxiety-Related Behavior

Traumatic brain injury (TBI) and long bone fractures are a common injury pattern in polytrauma patients and modulate each other's healing process. As only a limited number of studies have investigated both traumatic sites, we tested the hypothesis that brain-bone polytrauma mutually impacts neuro- and osteopathological outcomes. Adult female C57BL/6N mice were subjected to controlled cortical impact (CCI), and/or osteosynthetic stabilized femoral fracture (FF), or sham surgery. Neuromotor and behavioral impairments were assessed by neurological severity score, open field test, rotarod test, and elevated plus maze test. Brain and bone tissues were processed 42 days after trauma. CCI+FF polytrauma mice had increased bone formation as compared to FF mice and increased mRNA expression of bone sialoprotein (BSP). Bone fractures did not aggravate neuropathology or neuroinflammation assessed by cerebral lesion size, hippocampal integrity, astrocyte and microglia activation, and gene expression. Behavioral assessments demonstrated an overall impaired recovery of neuromotor function and persistent abnormalities in anxiety-related behavior in polytrauma mice. This study shows enhanced bone healing, impaired neuromotor recovery and anxiety-like behavior in a brain-bone polytrauma model. However, bone fractures did not aggravate TBI-evoked neuropathology, suggesting the existence of outcome-relevant mechanisms independent of the extent of brain structural damage and neuroinflammation.

Metabolomics provides insights into acceleration of bone healing in fractured patients with traumatic brain injuries

While clinical surveys have frequently reported that patients with traumatic brain injuries (TBIs) and comorbidities experience faster healing, the underlying mechanisms have been investigated but remain unclear. As a comprehensive comparison and analysis of the metabolic characteristics of these two pathologies have not been undertaken, we developed a rat model of fracture and TBI and collected serum samples for metabolomic analysis using ultra-high performance liquid chromatography-quadrupole time-of-flight MS (UHPLC-Q-TOF/MS). In total, we identified 40 differential metabolites and uncovered related pathways and potential mechanisms, including aminoacyl-transfer RNA biosynthesis; differential amino acids such as leucine, cholylhistidine, aspartyl-lysine; and related lipid metabolism, and discussed their impacts on bone formation in detail. This study highlights that the UHPLC-Q-TOF/MS-based metabolomics approach offers a better understanding of the metabolic links between TBI and accelerated bone recovery.

Neuroprotective Effects and Metabolomics Study of Protopanaxatriol (PPT) on Cerebral Ischemia/Reperfusion Injury In Vitro and In Vivo

Stroke, one of the leading causes of disability and death worldwide, is a severe neurological disease that threatens human life. Protopanaxatriol (PPT), panaxatriol-type saponin aglycone, is a rare saponin that exists in Panax ginseng and Panax Noto-ginseng. In this study, we established an oxygen-glucose deprivation (OGD)-PC12 cell model and middle cerebral artery occlusion/reperfusion (MCAO/R) model to evaluate the neuroprotective effects of PPT in vitro and in vivo. In addition, metabolomics analysis was performed on rat plasma and brain tissue samples to find relevant biomarkers and metabolic pathways. The results showed that PPT could significantly regulate the levels of LDH, MDA, SOD, TNF-α and IL-6 factors in OGD-PC12 cells in vitro. PPT can reduce the neurological deficit score and infarct volume of brain tissue in rats, restore the integrity of the blood-brain barrier, reduce pathological damage, and regulate TNF-α, IL-1β, IL-6, MDA, and SOD factors. In addition, the results of metabolomics found that PPT can regulate 19 biomarkers involving five metabolic pathways, including amino acid metabolism, arachidonic acid metabolism, sphingolipid metabolism, and glycerophospholipid metabolism. Thus, it could be inferred that PPT might serve as a novel natural agent for MCAO/R treatment.

Age related effects of selective and non-selective COX-2 inhibitors on bone healing

INTRODUCTION

Fractures are increasing worldwide and with an aging population, are frequent in the elderly. The healing of fractures progresses through various phases including the inflammatory stage. Aging is associated with slower healing and the use of non steroidal anti-inflammatory drugs (NSAIDs) may interrupt bone healing processes. We designed a study to compare the effect of diclofenac and celecoxib on fracture callus histomorphometry in a rat model of different age groups.

METHODS

Using 5 and 15 month old rats, fractures were induced on the left tibia and the animals allocated to receive one of the drugs. Animals were sacrificed at day 21 and 42 and the fracture callus harvested for processing and histological evaluation. Tissue proportions and histological grades were determined and compared across the groups.

RESULTS

Across all groups, the histological grade increased with time and animals in the young diclofenac group had the highest grade at day 42 (p = 0.004). The proportion of bone increased in all groups and was highest in the young diclofenac group at day 21 and day 42 (p = 0.003). Post hoc analysis showed that the young celecoxib and old celecoxib groups had the least proportion of bone (p = 0.032 and p = 0.003). The proportion of cartilage reduced in all groups at both time points.

CONCLUSION

Celecoxib was associated with lower histological grade and lower proportion of bone in older animals. We urge for caution regarding the use of celecoxib in older people for the management of pain associated with fractures. Diclofenac may be a better option in this group.

Correlation Between Traumatic Brain Injuries and Callus Formation in Long bone Fractures

INTRODUCTION

Orthopaedic aphorism teaches that fractures of long bones when associated with head injuries frequently heal with excessive callus and at a faster rate than normal. However, the evidence on this subject is flimsy and the aphorism remains unsubstantiated. Numerous studies have been conducted evaluating the possible humoral and other factors involved leading to excess callus formation in patients with a head injury. This study was designed to evaluate the effects of a traumatic head injury on bone healing in adults with a diaphyseal fracture of the lower limb.

METHODS

Fiveteen patients with a closed fracture of tibia or femur and associated head injury (cases) and 15 patients with a closed fracture of tibia or femur without an associated head injury (controls) were included in the study. All patients were evaluated in terms of various serum parameters, including IL-6, growth hormone, PTH, LDH, prolactin levels, and ALP. Head injuries were graded as mild, moderate, or severe. Ventilatory support if required was noted. Serum prolactin was repeated at 5 weeks. Patients were followed up with serial radiographs, and the volume of callus formed was calculated and compared.

RESULTS

The mean value of growth hormone, interleukin-6 levels, and prolactin levels at 5 weeks were found to be higher in patients with head injuries, and the difference was highly significant (p = 0.001). The severity of head injury also correlated proportionately with the spike in IL-6 levels. There was more pronounced callus formation in patients with head injury group when compared to the controls. This difference was significant at all intervals.

DISCUSSION

There was higher volume of callus noted at the end of 6 months in patients with severe head injury (GCS < 7) when compared to patients with moderate head injury (GCS > 7). The patients with severe head injury were naturally under ventilator support for a prolonged period compared to those with moderate head injury. It was thus indiscernible if the excess callus observed is due to the humoral cascade or as an effect of prolonged ventilation. Patients with head injuries show elevated parathyroid hormone levels, growth hormone levels at the time of injury, and elevated prolactin levels 5 weeks after the trauma-all of which might contribute to enhanced osteogenesis. Interleukin-6 levels are also elevated and the levels correlate to severity of head injury.

CONCLUSION

Head injury triggers a humoral cascade invloving interleukin-6, parathyroid hormoe, growth hormone, and prolactin that contributes to enhanced fracture healing.

Metabolic Abnormalities in Patients with Chronic Disorders of Consciousness

The vegetative state (VS) and minimally conscious state (MCS) are two major types of chronic disorders of consciousness (DoC). The assessment of these two consciousness states generally relies on the Coma Recovery Scale-Revised (CRS-R) score, but a high misdiagnosis rate limits the generalized use of this score. To identify metabolites in human plasma that can accurately distinguish VS from MCS patients, comprehensive plasma metabolic profiles were obtained with targeted metabolomics analysis and untargeted and targeted lipidomics analysis. Univariate and multivariate analyses were used to assess the significance of differences. Compared with healthy controls (HCs), the DoC groups, Emerged from Minimally Conscious State (EMCS) group and Alzheimer’s disease (AD) group had significantly different metabolic profiles. Purine metabolism pathway differed the most between the DoC (MCS and VS) and HC groups. In this pathway, adenosine, ADP, and AMP, which are the derived products of ATP degradation, were decreased in the MCS and VS groups compared to healthy controls. More importantly, we identified certain lipids for which the levels were enriched in the VS or MCS groups. Specifically, phosphatidylcholine, (38:5)-H (PC(38:5)-H), and arachidonic acid (AA) differed substantially between the VS and MCS groups and may be used to distinguish these two groups of patients. Together, our findings suggest that metabolic profiling is significantly altered in patients with chronic DoC.

Integrated metabolomics and network pharmacology to reveal the mechanisms of hydroxysafflor yellow A against acute traumatic brain injury

Traumatic brain injury (TBI) has become a leading cause of mortality, morbidity and disability worldwide. Hydroxysafflor yellow A (HSYA) is effective in treating TBI, but the potential mechanisms require further exploration. We aimed to reveal the mechanisms of HSYA against acute TBI by an integrated strategy combining metabolomics with network pharmacology. A controlled cortical impact (CCI) rat model was established, and neurological functions were evaluated. Metabolomics of brain tissues was used to identify differential metabolites, and the metabolic pathways were enriched by MetaboAnalyst. Then, network pharmacology was applied to dig out the potential targets against TBI induced by HSYA. The integrated network of metabolomics and network pharmacology was constructed based on Cytoscape. Finally, the obtained key targets were verified by molecular docking. HSYA alleviated the neurological deficits of TBI. Fifteen potentially significant metabolites were found to be involved in the therapeutic effects of HSYA against acute TBI. Most of these metabolites were regulated to recover after HSYA treatment. We found 10 hub genes according to network pharmacology, which was partly consistent with the metabolomics findings. Further integrated analysis focused on 4 key targets, including NOS1, ACHE, PTGS2 and XDH, as well as their related core metabolites and pathways. Molecular docking showed high affinities between key targets and HSYA. Region-specific metabolic alterations in the cortex and hippocampus were illuminated. This study reveals the complicated mechanisms of HSYA against acute TBI. Our work provides a novel paradigm to identify the potential mechanisms of pharmacological effects derived from a natural compound.

Crosstalk of Brain and Bone-Clinical Observations and Their Molecular Bases

As brain and bone disorders represent major health issues worldwide, substantial clinical investigations demonstrated a bidirectional crosstalk on several levels, mechanistically linking both apparently unrelated organs. While multiple stress, mood and neurodegenerative brain disorders are associated with osteoporosis, rare genetic skeletal diseases display impaired brain development and function. Along with brain and bone pathologies, particularly trauma events highlight the strong interaction of both organs. This review summarizes clinical and experimental observations reported for the crosstalk of brain and bone, followed by a detailed overview of their molecular bases. While brain-derived molecules affecting bone include central regulators, transmitters of the sympathetic, parasympathetic and sensory nervous system, bone-derived mediators altering brain function are released from bone cells and the bone marrow. Although the main pathways of the brain-bone crosstalk remain ‘efferent’, signaling from brain to bone, this review emphasizes the emergence of bone as a crucial ‘afferent’ regulator of cerebral development, function and pathophysiology. Therefore, unraveling the physiological and pathological bases of brain-bone interactions revealed promising pharmacologic targets and novel treatment strategies promoting concurrent brain and bone recovery.

M2 macrophages are closely associated with accelerated clavicle fracture healing in patients with traumatic brain injury: a retrospective cohort study

Background

Mounting evidence indicate patients with traumatic brain injury (TBI) have an accelerated fracture healing. The healing process of bone fractures is greatly dependent on infiltrated macrophages. The macrophages are categorized into M1 or M2 phenotypes with different functions. This study is aimed to address the potential role of subtypes of macrophages in the process of fracture healing in patients with TBI.

Methods

Twenty-five cases of clavicle fracture alone (CF group) and 22 cases of clavicle fracture concomitant with TBI (CFT group) were retrospectively analyzed in this study. Callus tissues were harvested during operations. The expressions of COX-2, CD206, and CD68 were measured with immunohistochemistry.

Results

The percentages of M2 macrophages in total macrophages increased after bone fracture in both groups, while the percentages of M1-type macrophages are decreased. Interestingly, the increased percentages of M2 macrophages are significantly higher in CFT group than in CF group. Compared to CF group, the fracture callus volume was much larger (21.9 vs 8.5 cm³) and the fracture healing time was much shorter (82.2 vs 127.0 days) in CFT group. The percentage of M2 macrophages was negatively correlated with fracture healing time in patients (r = − 0.575, p < 0.01).

Conclusions

The findings suggest that the percentages of M2 macrophages in callus tissues increased dramatically during the repairing stage in both CF and CFT group. Percentages of M2 macrophages are associated with accelerated fracture healing in patients with TBI. M2 macrophage polarization during the stage of bone regeneration may play a vital role in promoting bone fracture healing.

20-HETE Inhibition by HET0016 Decreases the Blood-Brain Barrier Permeability and Brain Edema After Traumatic Brain Injury

Recent studies have implicated 20-HETE as a vasoconstrictive mediator in trauma, the purpose of this study was to determine whether administration of HET0016, the 20-HETE inhibitor, could protect neurons from trauma and the effect of HET0016 on the blood–brain barrier (BBB) and brain edema in experimental traumatic brain injury (TBI). Rat models with TBI were established. Brain edema was measured according to the wet and dry weight method at 3, 24, and 72 h after injury. The BBB permeability was quantified by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Superoxide production, the activity of superoxide dismutase (SOD) and total antioxidative capability (T-AOC) in traumatic brain tissues were also measured. Western blot analysis was used to analyze the expression of the occludin, ZO-1, Matrix metalloproteinase-9 (MMP-9), and c-Jun N-terminal protein kinase (JNK) pathways. At 24 and 72 h after administration of HET0016 following TBI, the BBB permeability and brain edema decreased. The decrease in superoxide production and the increase in the activity of SOD and T-AOC were measured in this study. Western blot analysis showed that the expression of MMP-9 and JNK pathways was suppressed, but the expression of ZO-1 and occludin was increased. These results suggest that the administration of HET0016 could protect the BBB function and decrease brain edema after experimental traumatic injury by suppressing the expression of MMP-9 and activating the expression of tight junction proteins via suppressing the JNK pathway and oxidative stress.

Discovery of Lipidome Alterations Following Traumatic Brain Injury via High-Resolution Metabolomics

Traumatic brain injury (TBI) can occur across wide segments of the population, presenting in a heterogeneous manner that makes diagnosis inconsistent and management challenging. Biomarkers offer the potential to objectively identify injury status, severity, and phenotype by measuring the relative concentrations of endogenous molecules in readily accessible biofluids. Through a data-driven, discovery approach, novel biomarker candidates for TBI were identified in the serum lipidome of adult male Sprague-Dawley rats in the first week following moderate controlled cortical impact (CCI). Serum samples were analyzed in positive and negative modes by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). A predictive panel for the classification of injured and uninjured sera samples, consisting of 26 dysregulated species belonging to a variety of lipid classes, was developed with a cross-validated accuracy of 85.3% using omniClassifier software to optimize feature selection. Polyunsaturated fatty acids (PUFAs) and PUFA-containing diacylglycerols were found to be upregulated in sera from injured rats, while changes in sphingolipids and other membrane phospholipids were also observed, many of which map to known secondary injury pathways. Overall, the identified biomarker panel offers viable molecular candidates representing lipids that may readily cross the blood-brain barrier (BBB) and aid in the understanding of TBI pathophysiology.

Roles of elevated 20‑HETE in the breakdown of blood brain barrier and the severity of brain edema in experimental traumatic brain injury

Breakdown of the blood brain barrier (BBB) is a secondary injury following traumatic brain injury (TBI) and can lead to the development of brain edema. However, the factors that contribute to the disruption of the BBB and increase the severity of brain edema in TBI remain to be elucidated. 20‑hydroxyeicosatetraenoic acid (20‑HETE) is a metabolite of arachidonic acid. The inhibition of 20‑HETEsynthesis by HET0016 has been suggested as a strategy to decrease brain edema. The present study aimed to investigate whether the elevated production of 20‑HETE in cerebral tissue may contribute to BBB breakdown and increase the severity of brain edema in rats with TBI. BBB permeability was quantified using dynamic contrast‑enhanced magnetic resonance imaging and brain edema was measured according to brain water content. Superoxide production in injured tissue was also assessed. Liquid chromatography‑mass spectrometry was used to evaluate 20‑HETE production in injured tissue. Western blot analysis was used to assess the expression of occludin, zonula occludens (ZO)‑1, matrix metalloproteinase (MMP)‑9, and proteins of the c‑Jun N‑terminal kinase (JNK) pathway. A total of 3, 24 and 72 h following the induction of TBI, 20‑HETE levels, BBB permeability and brain edema were identified to be increased, accompanied by an increase in superoxide production. Conversely, superoxide dismutase levels, in addition to the total antioxidative capability were decreased. In addition, the expression of MMP‑9 and proteins of the JNK pathway was upregulated, whereas the expression of occludin and ZO‑1 was observed to be suppressed. These results suggested that 20‑HETE may aggravate BBB disruption following TBI, via enhancing the expression of MMP‑9 and tight junction proteins. Furthermore, oxidative stress and the JNK signaling pathway may be involved in BBB dysregulation. In conclusion, the results of the present demonstrated that the production of 20‑HETE was increased in cerebral tissue following traumatic injury, thus suggesting that it may contribute to the compromise of BBB integrity and the development of brain edema.

Clinical and Basic Evaluation of the Prognostic Value of Uric Acid in Traumatic Brain Injury

Background: As a major antioxidant in serum, uric acid (UA) was once considered only as the leading cause of gout; however, recent studies have validated its neuroprotective role in ischemic stroke. Because the potential protective effects of UA in traumatic brain injury (TBI) remain largely unknown, this study investigated the role of UA in TBI in both clinical patients and experimental animals. Methods: In TBI patients, serum UA concentrations were measured within 3 days after injury. Clinical outcomes at discharge were classified according to the Glasgow Outcome Scale: good outcome (4-5) and poor outcome (1-3). Risk factors for good outcome were identified via backward logistic regression analysis. For the animal study, a controlled cortical impact (CCI) injury model was established in mice. These mice were given UA at different doses intraperitoneally, and subsequent UA concentrations in mouse serum and brain tissue were determined. Neurological function, oxidative stress, inflammatory response, neuronal maintenance, cerebral blood flow, and lesion size were also assessed. Results: The serum UA level was significantly lower in TBI patients who had a good outcome (P<0.01), and low serum UA was an independent predictor of good outcome after TBI (P<0.01; odds ratio, 0.023; 95% confidence interval, 0.006-0.082). Consistently, decreased levels of serum UA were observed in both TBI patients and CCI animals (P<0.05), whereas the UA concentration was increased in CCI brain tissue (P<0.05). Administration of UA further increased the UA level in brain tissue as compared to that in control animals (P<0.05). Among the different doses administered, 16 mg/kg UA improved sensorimotor functional recovery, spatial learning, and memory in CCI mice (P<0.05). Moreover, oxidative stress and the inflammatory response were inhibited by UA treatment (P<0.05). UA treatment also improved neuronal maintenance and cortical blood flow (P<0.05) but not lesion size (P>0.05). Conclusions: UA acted to attenuate neuronal loss, cerebral perfusion impairment and neurological deficits in TBI mice through suppression of neuronal and vascular oxidative stress. Following TBI, active antioxidant defense in the brain may result in consumption of UA in the serum, and thus, a decreased serum UA level could be predictive of good clinical recovery.

Cytochrome P450 eicosanoids in cerebrovascular function and disease

Cytochrome P450 eicosanoids play important roles in brain function and disease through their complementary actions on cell-cell communications within the neurovascular unit (NVU) and mechanisms of brain injury. Epoxy- and hydroxyeicosanoids, respectively formed by cytochrome P450 epoxygenases and ω-hydroxylases, play opposing roles in cerebrovascular function and in pathological processes underlying neural injury, including ischemia, neuroinflammation and oxidative injury. P450 eicosanoids also contribute to cerebrovascular disease risk factors, including hypertension and diabetes. We summarize studies investigating the roles P450 eicosanoids in cerebrovascular physiology and disease to highlight the existing balance between these important lipid signaling molecules, as well as their roles in maintaining neurovascular homeostasis and in acute and chronic neurovascular and neurodegenerative disorders.

Metabolomics reveals the effect of Xuefu Zhuyu Decoction on plasma metabolism in rats with acute traumatic brain injury

Xuefu Zhuyu Decoction (XFZY), an important traditional Chinese herbal formula, has been reported effective on traumatic brain injury (TBI) in rats. However, its cerebral protection mechanism has not been clarified at the metabolic level. This work aims to explore the global metabolic characteristics of XFZY in rats during the acute phase of TBI on days 1 and 3. A plasma metabolomics method based on gas chromatography-mass spectrometry coupled with univariate analysis and multivariate statistical analysis was performed in three groups (Sham, Vehicle, XFZY). Then, a pathway analysis using MetaboAnalyst 3.0 was performed to illustrate the pathways of therapeutic action of XFZY in TBI. XFZY treatment attenuates neurological dysfunction and cortical lesion volume post-injury on day 3, and reverses the plasma metabolite abnormalities (glutamic acid, lactic acid, 3-hydroxybutyric acid, and ribitol, etc.). These differential metabolites are mainly involved in D-glutamine and D-glutamate metabolism, alanine, aspartate and glutamate metabolism, and inositol phosphate metabolism. Our study reveals potential biomarkers and metabolic networks of acute TBI and neuroprotection effects of XFZY, and shows this metabolomics approach with MetaboAnalyst would be a feasible way to systematically study therapeutic effects of XFZY on TBI.

Current and Emerging Technologies for Probing Molecular Signatures of Traumatic Brain Injury

Traumatic brain injury (TBI) is understood as an interplay between the initial injury, subsequent secondary injuries, and a complex host response all of which are highly heterogeneous. An understanding of the underlying biology suggests a number of windows where mechanistically inspired interventions could be targeted. Unfortunately, biologically plausible therapies have to-date failed to translate into clinical practice. While a number of stereotypical pathways are now understood to be involved, current clinical characterization is too crude for it to be possible to characterize the biological phenotype in a truly mechanistically meaningful way. In this review, we examine current and emerging technologies for fuller biochemical characterization by the simultaneous measurement of multiple, diverse biomarkers. We describe how clinically available techniques such as cerebral microdialysis can be leveraged to give mechanistic insights into TBI pathobiology and how multiplex proteomic and metabolomic techniques can give a more complete description of the underlying biology. We also describe spatially resolved label-free multiplex techniques capable of probing structural differences in chemical signatures. Finally, we touch on the bioinformatics challenges that result from the acquisition of such large amounts of chemical data in the search for a more mechanistically complete description of the TBI phenotype.

Plasma metabolomics profiles in rats with acute traumatic brain injury

Traumatic brain injury (TBI) is a major cause of mortality and disability worldwide. We validated the utility of plasma metabolomics analysis in the clinical diagnosis of acute TBI in a rat model of controlled cortical impact (CCI) using gas chromatography/mass spectrometry (GC/MS). Thirty Sprague-Dawley rats were randomly divided into two groups of 15 rats each: the CCI group and sham group. Blood samples were obtained from the rats within the first 24 h after TBI injury. GC/MS measurements were performed to evaluate the profile of acute TBI-induced metabolic changes, resulting in the identification of 45 metabolites in plasma. Principal component analysis, partial least squares-discriminant analysis, orthogonal partial least square discriminant analysis using hierarchical clustering and univariate/multivariate analyses revealed clear differences in the plasma metabolome between the acute CCI group and the sham group. CCI induced distinctive changes in metabolites including linoleic acid metabolism, amino acid metabolism, galactose metabolism, and arachidonic acid metabolism. Specifically, the acute CCI group exhibited significant alterations in proline, phosphoric acid, β-hydroxybutyric acid, galactose, creatinine, L-valine, linoleic acid and arachidonic acid. A receiver operating characteristic curve analysis showed that the above 8 metabolites in plasma could be used as the potential biomarkers for the diagnosis of acute TBI. Furthermore, this study is the first time to identify the galactose as a biomarker candidate for acute TBI. This comprehensive metabolic analysis complements target screening for potential diagnostic biomarkers of acute TBI and enhances predictive value for the therapeutic intervention of acute TBI.

[Research progress of correlation between traumatic brain injury and fracture healing]

Objective

To review the current status and advances of the correlation between traumatic brain injury (TBI) and fracture healing.

Methods

The related domestic and abroad literature about the correlation between TBI and fracture healing was extensively reviewed and analyzed.

Results

There are a variety of studies on the correlation between TBI and fracture healing, which can be divided into two major aspects: revascularization and osteogenesis; the local and systemic changes of the neuropeptide and hormone after TBI.

Conclusion

TBI facilitates callus formation, the further research is needed to clarify the exact mechanism.

Mild TBI Results in a Long-Term Decrease in Circulating Phospholipids in a Mouse Model of Injury

Neurophysiological and neurological dysfunction is usually experienced for a short period of time in patients with mild traumatic brain injury (mTBI). However, around 15 % of patients exhibit symptoms months after TBI. Phospholipid (PL) changes have been observed in plasma from mTBI patients at chronic stages, suggesting a role in TBI pathology. We examined long-term plasma phospholipid profiles in a mouse model of mTBI to determine their translational value in reproducing PL changes observed in mTBI patients. Plasma samples were collected at an acute timepoint (24 h post-injury) and at several chronic stages (3, 6, 12 and 24 months post-injury) from injured mice and sham controls. Phospholipids were identified and quantified using liquid chromatography/mass spectrometry analysis. In accordance with human data, we observed significantly lower levels of several major PL classes in mTBI mice compared to controls at chronic timepoints. Saturated, monounsaturated and polyunsaturated fatty acids (PUFAs) were differently regulated over time. As PUFA levels were decreased at 3 months, we measured levels of malondialdehyde to assess lipid peroxidation, which we found to be elevated at this timepoint. Ether-containing PE species were elevated at 24 h post-injury and decreased relative to controls at chronic stages. Arachidonic acid and docosahexaenoic acid-containing species were significantly decreased within all PL classes at the chronic stages. Our findings are similar to changes in PL levels observed in human mTBI subjects. Chronic TBI biomarkers have received little attention, even though disabilities at this stage can be of major importance. Our study provides information on biochemical abnormalities that persist long after the initial injury; these abnormalities may provide useful insight into the continuing pathogenesis and serve as diagnostic biomarkers.

Serum Metabolic Profiling Reveals Altered Metabolic Pathways in Patients with Post-traumatic Cognitive Impairments

Cognitive impairment, the leading cause of traumatic brain injury (TBI)-related disability, adversely affects the quality of life of TBI patients, and exacts a personal and economic cost that is difficult to quantify. The underlying pathophysiological mechanism is currently unknown, and an effective treatment of the disease has not yet been identified. This study aimed to advance our understanding of the mechanism of disease pathogenesis; thus, metabolomics based on gas chromatography/mass spectrometry (GC-MS), coupled with multivariate and univariate statistical methods were used to identify potential biomarkers and the associated metabolic pathways of post-TBI cognitive impairment. A biomarker panel consisting of nine serum metabolites (serine, pyroglutamic acid, phenylalanine, galactose, palmitic acid, arachidonic acid, linoleic acid, citric acid, and 2,3,4-trihydroxybutyrate) was identified to be able to discriminate between TBI patients with cognitive impairment, TBI patients without cognitive impairment and healthy controls. Furthermore, associations between these metabolite markers and the metabolism of amino acids, lipids and carbohydrates were identified. In conclusion, our study is the first to identify several serum metabolite markers and investigate the altered metabolic pathway that is associated with post-TBI cognitive impairment. These markers appear to be suitable for further investigation of the disease mechanisms of post-TBI cognitive impairment.

Xuefu Zhuyu decoction, a traditional Chinese medicine, provides neuroprotection in a rat model of traumatic brain injury via an anti-inflammatory pathway

Neuroinflammation is central to the pathology of traumatic brain injury (TBI). Xuefu Zhuyu decoction (XFZY) is an effective traditional Chinese medicine to treat TBI. To elucidate its potential molecular mechanism, this study aimed to demonstrate that XFZY functions as an anti-inflammatory agent by inhibiting the PI3K-AKT-mTOR pathway. Sprague-Dawley rats were exposed to controlled cortical impact to produce a neuroinflammatory response. The treatment groups received XFZY (9 g/kg and 18 g/kg), Vehicle group and Sham group were gavaged with equal volumes of saline. The modified neurologic severity score (mNSS) and the Morris water maze test were used to assess neurological deficits. Arachidonic acid (AA) levels in brain tissue were measured using tandem gas chromatography-mass spectrometry. TNF-α and IL-1β levels in injured ipsilateral brain tissue were detected by ELISA. AKT and mTOR expression were measured by western blot analysis. The results indicated that XFZY significantly enhanced spatial memory acquisition. XFZY (especially at a dose of 9 g/kg) markedly reduced the mNSS and levels of AA, TNF-α and IL-1β. Significant downregulation of AKT/mTOR/p70S6K proteins in brain tissues was observed after the administration of XFZY (especially at a dose of 9 g/kg). XFZY may be a promising therapeutic strategy for reducing inflammation in TBI.

Arachidonic acid promotes skin wound healing through induction of human MSC migration by MT3-MMP-mediated fibronectin degradation

Arachidonic acid (AA) is largely released during injury, but it has not been fully studied yet how AA modulates wound repair with stem cells. Therefore, we investigated skin wound-healing effect of AA-stimulated human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in vivo and its molecular mechanism in vitro. We found that transplantation of hUCB-MSCs pre-treated with AA enhanced wound filling, re-epithelization, and angiogenesis in a mouse skin excisional wound model. AA significantly promoted hUCB-MSCs migration after a 24 h incubation, which was inhibited by the knockdown of G-protein-coupled receptor 40 (GPR40). AA activated mammalian target of rapamycin complex 2 (mTORC2) and Akt^ser473 through the GPR40/phosphoinositide 3-kinase (PI3K) signaling, which was responsible for the stimulation of an atypical protein kinase C (PKC) isoform, PKCζ. Subsequently, AA stimulated phosphorylation of p38 MAPK and transcription factor Sp1, and induced membrane type 3-matrix metalloproteinase (MT3-MMP)-dependent fibronectin degradation in promoting hUCB-MSCs motility. Finally, the silencing of MT3-MMP in AA-stimulated hUCB-MSCs failed to promote the repair of skin wounds owing to impaired cell motility. In conclusion, AA enhances skin wound healing through induction of hUCB-MSCs motility by MT3-MMP-mediated fibronectin degradation, which relies on GPR40-dependent mTORC2 signaling pathways.

Improved fracture healing in patients with concomitant traumatic brain injury: proven or not?

Over the last 3 decades, scientific evidence advocates an association between traumatic brain injury (TBI) and accelerated fracture healing. Multiple clinical and preclinical studies have shown an enhanced callus formation and an increased callus volume in patients, respectively, rats with concomitant TBI. Over time, different substances (cytokines, hormones, etc.) were in focus to elucidate the relationship between TBI and fracture healing. Until now, the mechanism behind this relationship is not fully clarified and a consensus on which substance plays the key role could not be attained in the literature. In this review, we will give an overview of current concepts and opinions on this topic published in the last decade and both clinical and pathophysiological theories will be discussed.

Craniocerebral injury promotes the repair of peripheral nerve injury

The increase in neurotrophic factors after craniocerebral injury has been shown to promote fracture healing. Moreover, neurotrophic factors play a key role in the regeneration and repair of peripheral nerve. However, whether craniocerebral injury alters the repair of peripheral nerve injuries remains poorly understood. Rat injury models were established by transecting the left sciatic nerve and using a free-fall device to induce craniocerebral injury. Compared with sciatic nerve injury alone after 6–12 weeks, rats with combined sciatic and craniocerebral injuries showed decreased sciatic functional index, increased recovery of gastrocnemius muscle wet weight, recovery of sciatic nerve ganglia and corresponding spinal cord segment neuron morphologies, and increased numbers of horseradish peroxidase-labeled cells. These results indicate that craniocerebral injury promotes the repair of peripheral nerve injury.

A review of analytical methods for eicosanoids in brain tissue

Eicosanoids are potent lipid mediators of inflammation and are known to play an important role in numerous pathophysiological processes. Furthermore, inflammation has been proven to be a mediator of diseases such as hypertension, atherosclerosis, Alzheimer's disease, cancer and rheumatoid arthritis. Hence, these lipid mediators have gained significant attention in recent years. This review focuses on chromatographic and mass spectrometric methods that have been used to analyze arachidonic acid and its metabolites in brain tissue. Recently published analytical methods such as LC-MS/MS and GC-MS/MS are discussed and compared in terms of limit of quantitation and sample preparation procedures, including solid phase extraction and derivatization. Analytical challenges are also highlighted.