Evidence for the role of PI3-kinase-AKT-eNOS signalling pathway in secondary inflammatory process after spinal cord compression injury in mice

Acupuncture attenuates renal interstitial fibrosis via the TGF‑β/Smad pathway

Acupuncture is one of the most useful tools in complimentary medicine, and has demonstrated potential value for treating chronic renal failure (CRF). However, the underlying mechanisms for its therapeutic effect remain unknown. In the present study, the effects of acupuncture on renal interstitial fibrosis (RIF) were explored in a rabbit model of CRF. Rabbits were assigned to the following five groups: sham, model, losartan potassium (Posi), acupuncture (Acup) and acupuncture+inhibitor (Acup+Inhib) groups. The CRF rabbits were administered a drug or/and acupuncture on Shenshu, Mingmen and Pishu. The body weights, urine protein, serum creatinine (SCr) and blood urea nitrogen (BUN) levels of the rabbits were measured. Transforming growth factor β (TGF-β), integrin-linked kinase (ILK) and Smad3 expression were detected by qRT-PCR. Tumor necrosis factor-α (TNF-α) and endothelial nitric oxide synthase (eNOS) expression were analyzed by western blot methods. The concentrations of TGF-β, IL-8, TNF-α and IL-1β in blood serum were detected using ELISA kits. In addition, pathological characteristics of the rabbit tissues were evaluated by H&E and Masson's trichrome staining methods, and TGF-β expression was detected by immunohistochemistry (IHC) assays. Results showing decreased body weights and increased urine protein, SCr and BUN levels confirmed that the CRF model had been successfully constructed. It was also found that acupuncture significantly reduced the levels of TNF-α, Smad3, ILK and TGF-β expression, dramatically decreased the concentrations of TGF-β, IL-8, TNF-α and IL-1β in blood serum, and significantly increased eNOS expression in the CRF model rabbits by affecting the TGF-β/Smad signaling pathway. In addition, it was demonstrated that acupuncture could relieve RIF by affecting the TGF-β/Smad pathway. These observations indicate that acupuncture may be useful for treating CRF, and suggest the TGF-β/Smad pathway as a target for CRF therapy.

LncRNA SNHG5 enhances astrocytes and microglia viability via upregulating KLF4 in spinal cord injury

This study aims to explore the role and mechanism of lncRNA SNHG5 in spinal cord injury (SCI). The interaction between SNHG5 and Krüppel-like factor 4 (KLF4) was verified by RNA pull-down and RNA immunoprecipitation (RIP) assay. Rat neural function was evaluated by BBB and BMS scores. Results showed that GFAP and Iba-1 (specific proteins for astrocytes and microglia respectively) were upregulated in spinal cord of SCI rats. Simultaneously, spinal cord also expressed substantially higher levels of SNHG5, KLF4 and eNOS (endothelial Nitric Oxide Synthase) than sham group. In traumatically injured astrocytes and microglia, SNHG5 overexpression increased cells viability, which was significantly inhibited by SNHG5 knockdown. KLF4 is a directly target for SNHG5 and is positively regulated by SNHG5. The knockdown of KLF4 effectively decreased astrocytes and microglia viability induced by SHNG5 overexpression and attenuated the pcDNA-SNHG5-mediated repression of the apoptosis. In SCI rats, the injection of Lenti-SNHG5 reduced BBB and BMS scores and also enhanced the protein expression of KLF4, eNOS, GFAP and Iba-1. In summary, our data suggested that SNHG5 promotes SCI via increasing the viability of astrocytes and microglia. The mechanism by which SNHG5 works is its directive interaction to KLF4 and contribution to eNOS upregulation.

Effect of TERT on the growth of fibrosarcoma via caspase-3, survivin and PKB

The present study explored the effect of telomerase reverse transcriptase (TERT) on the growth and apoptosis of fibrosarcoma, and investigated the potential molecular signalling pathways underlying its effect. A plasmid was constructed in order to overexpress TERT and siRNA was used to knockdown TERT. The effect of TERT on fibrosarcoma cells in vitro was studied by performing reverse transcription-quantitative PCR and western blotting to determine the expression of p53, survivin, caspase-3, caspase-7 and PKB. Knockdown of TERT suppressed cell growth, decreased fibrosarcoma volume, decreased survivin and PKB expression, and increased caspase-3 expression. The results of the present study suggest that TERT regulates the growth of fibrosarcoma in vitro and in vivo, and that this is associated with the expression of caspase-3 and survivin, in addition to the PKB signalling pathway.

Neurotrophic factor and Trk signaling mechanisms underlying the promotion of motor recovery after acute spinal cord injury in rats

Neurotrophic factor (NF) and Trk signaling mechanisms underlying the promotion of motor recovery following acute spinal cord injury (SCI) in rats were investigated. Thirty-six adult Sprague-Dawley rats of both genders were randomly divided into three groups: Sham-operated, model, and NF/Trk. Each group consisted of 12 rats, with four subgroups in each group: 1, 3, 5 and 7 days. Sham-operated rats received a laminectomy without SCI, while in model group rats, SCI was induced using an improved version of the Allen's method. After analepsia, sham-operated and model group rats were given normal saline via gavage, while the NF/Trk group received NFs and Trk. Lower limb function was measured using the Basso, Beattie and Bresnahan scale 1, 3, 5 and 7 days before and after surgery. Results were analyzed statistically. Six rats from each group were randomly selected for sacrifice at 1, 3, 5 and 7 days after the operation. Morphological changes in motor neurons in the anterior gray column were observed by hematoxylin and eosin, and Nissl staining. Brain-derived expression of NF (BNDF) and neurotrophin-3 (NT-3) was detected by immunofluorescence, and the number of positive cells was counted. Expression of Trk B and Trk protein C receptor was measured by western blotting. In the NF/Trk group, the expression of NF/Trk pathway components remarkably increased. In addition, the morphology of motor neurons in the anterior gray column was improved. Expression of BNDF and NT-3 was significantly increased in motor neurons of the anterior gray column in NF/Trk rats compared with those of sham-operated and model rats (P<0.05). NFs promote motor recovery following acute SCI in rats and may have valuable clinical applications.

MicroRNA-126 suppresses inflammation in endothelial cells under hyperglycemic condition by targeting HMGB1

MicroRNA-126(miR-126) targets involved in inflammation need to be identified. In this study, we aim to investigate whether high-mobility group box 1(HMGB1), an inflammation-related gene, is the target of miR-126 in diabetic vascular endothelium. The diabetic apoE^-/- mice model, a classical diabetic atherosclerosis model, was established. The aorta of diabetic apoE^-/- mice showed decrease of miR-126 and elevation of HMGB1 and inflammation. Next, we employed several in vitro experiments to address the role of miRNA-126 on the regulation of HMGB1 in endothelial cells under hyperglycemic and inflammatory conditions. Manipulation of miRNA levels in human umbilical vein endothelial cells (HUVECs) was achieved by transfecting cells with miR-126 mimic and antagomir. Overexpression of miR-126 could decrease the expression of downstream components of HMGB1 including TNF-α, ROS, and NADPH oxidase activity in HUVECs under hyperglycemic condition. Nevertheless, such phenomenon was completely reversed by miR-126 antagomir. The expression of HMGB1 protein rather than HMGB1 mRNA was down-regulated after transfection with miR-126 mimic, which indicated the modulation of HMGB1 mediated by miR-126 was at the posttranslational level. Luciferase reporter assay confirmed the 3'-UTR of HMGB1 gene was a direct target of miR-126. Western blot analysis also indicated that overexpression of miR-126 contributed to the elevation of p-eNOS, eNOS and p-AKT expressions, respectively. In summary, our findings suggest that miR-126 may suppress inflammation and ROS production in endothelial cells treated by high glucose through modulating the expression of HMGB1. Our study provides a novel pathogenic link between dysregulated miRNA expression and inflammation in diabetic vascular endothelium.

Neuroprotective and Neurorestorative Processes after Spinal Cord Injury: The Case of the Bulbospinal Respiratory Neurons

High cervical spinal cord injuries interrupt the bulbospinal respiratory pathways projecting to the cervical phrenic motoneurons resulting in important respiratory defects. In the case of a lateralized injury that maintains the respiratory drive on the opposite side, a partial recovery of the ipsilateral respiratory function occurs spontaneously over time, as observed in animal models. The rodent respiratory system is therefore a relevant model to investigate the neuroplastic and neuroprotective mechanisms that will trigger such phrenic motoneurons reactivation by supraspinal pathways. Since part of this recovery is dependent on the damaged side of the spinal cord, the present review highlights our current understanding of the anatomical neuroplasticity processes that are developed by the surviving damaged bulbospinal neurons, notably axonal sprouting and rerouting. Such anatomical neuroplasticity relies also on coordinated molecular mechanisms at the level of the axotomized bulbospinal neurons that will promote both neuroprotection and axon growth.

Co-Ultramicronized Palmitoylethanolamide/Luteolin Promotes Neuronal Regeneration after Spinal Cord Injury

Spinal cord injury (SCI) stimulates activation of astrocytes and infiltration of immune cells at the lesion site; however, the mechanism that promotes the birth of new neurons is still under debate. Neuronal regeneration is restricted after spinal cord injury, but can be stimulated by experimental intervention. Previously we demonstrated that treatment co-ultramicronized palmitoylethanolamide and luteolin, namely co-ultraPEALut, reduced inflammation. The present study was designed to explore the neuroregenerative properties of co-ultraPEALut in an estabished murine model of SCI. A vascular clip was applied to the spinal cord dura at T5-T8 to provoke injury. Mice were treated with co-ultraPEALut (1 mg/kg, intraperitoneally) daily for 72 h after SCI. Co-ultraPEALut increased the numbers of both bromodeoxyuridine-positive nuclei and doublecortin-immunoreactive cells in the spinal cord of injured mice. To correlate neuronal development with synaptic plasticity a Golgi method was employed to analyze dendritic spine density. Co-ultraPEALut administration stimulated expression of the neurotrophic factors brain-derived neurotrophic factor, glial cell-derived neurotrophic factor, nerve growth factor, and neurotrophin-3. These findings show a prominent effect of co-ultraPEALut administration in the management of survival and differentiation of new neurons and spine maturation, and may represent a therapeutic treatment for spinal cord and other traumatic diseases.

The Incremental Induction of Neuroprotective Properties by Multiple Therapeutic Strategies for Primary and Secondary Neural Injury

Neural diseases including injury by endogenous factors, traumatic brain injury, and degenerative neural injury are eventually due to reactive oxygen species (ROS). Thus ROS generation in neural tissues is a hallmark feature of numerous forms of neural diseases. Neural degeneration and the neural damage process is complex, involving a vast array of tissue structure, transcriptional/translational, electrochemical, metabolic, and functional events within the intact neighbors surrounding injured neural tissues. During aging, multiple changes involving physical, chemical, and biochemical processes occur from the molecular to the morphological levels in neural tissues. Among many recommended therapeutic candidates, melatonin also plays a role in protecting the nervous system from anti-inflammation and efficiently safeguards neuronal cells via antioxidants and other endogenous/exogenous beneficial factors. Therefore, given the wide range of mechanisms responsible for neuronal damage, multi-action drugs or therapies for the treatment of neural injury that make use of two or more agents and target several pathways may have greater efficacy in promoting functional recovery than a single therapy alone.

Transforming growth factor β-induced expression of chondroitin sulfate proteoglycans is mediated through non-Smad signaling pathways

The expression of chondroitin sulfate proteoglycans (CSPGs) by reactive astrocytes is a major factor contributing to glial scarring and regenerative failure after spinal cord injury, but the molecular mechanisms underlying CSPG expression remain largely undefined. One contributing factor is transforming growth factor β (TGFβ), which is upregulated after injury and has been shown to induce expression of CSPGs in vitro. TGFβ typically mediates its effects through the Smad2/3 signaling pathway, and it has been suggested that this pathway is responsible for CSPG expression. However, there is evidence that TGFβ can also activate non-Smad signaling pathways. In this study, we report that TGFβ-induced expression of three different CSPGs--neurocan, brevican, and aggrecan--is mediated through non-Smad signaling pathways. We observed significant increases in TGFβ-induced expression of neurocan, brevican, and aggrecan following siRNA knockdown of Smad2 or Smad4, which indicates that Smad signaling is not required for the expression of these CSPGs. In addition, we show that neurocan, aggrecan, and brevican levels are significantly reduced when TGFβ is administered in the presence of either the PI3K inhibitor LY294002 or the mTOR inhibitor rapamycin, but not the MEK1/2 inhibitor U0126. This suggests that TGFβ mediates this effect through non-Smad-dependent activation of the PI3K-Akt-mTOR signaling pathway, and targeting this pathway may therefore be an effective means of reducing CSPG expression in the injured CNS.

Notch1 cardioprotection in myocardial ischemia/reperfusion involves reduction of oxidative/nitrative stress

Oxidative/nitrative stress plays an important role in myocardial ischemia/reperfusion (MI/R) injury. Notch1 participates in the regulation of cardiogenesis and cardiac response to hypertrophic stress, but the function of Notch1 signaling in MI/R has not been explored. This study aims to determine the role of Notch1 in MI/R, and investigate whether Notch1 confers cardioprotection. Notch1 specific small interfering RNA (siRNA, 20 μg) or Jagged1 (a Notch ligand, 12 μg) was delivered through intramyocardial injection. 48 h after injection, mice were subjected to 30 min of myocardial ischemia followed by 3 h (for cell apoptosis and oxidative/nitrative stress), 24 h (for infarct size and cardiac function), or 2 weeks (for cardiac fibrosis and function) of reperfusion. Cardiac-specific Notch1 knockdown resulted in significantly aggravated I/R injury, as evidenced by enlarged infarct size, depressed cardiac function, increased myocardial apoptosis and cardiac fibrosis. Downregulation of Notch1 increased expression of inducible NO synthase (iNOS) and gp(91phox), enhanced the production of NO metabolites and superoxide, as well as their cytotoxic reaction product peroxynitrite. Moreover, Notch1 blockade also reduced phosphorylation of endothelial NO synthase (eNOS) and Akt, and increased expression of PTEN, a key phosphatase involved in the regulation of Akt phosphorylation. In addition, activation of Notch1 by Jagged1 or administration of peroxynitrite scavenger reduced production of peroxynitrite and attenuated MI/R injury. These data indicate that Notch1 signaling protects against MI/R injury partly though PTEN/Akt mediated anti-oxidative and anti-nitrative effects.

A new co-ultramicronized composite including palmitoylethanolamide and luteolin to prevent neuroinflammation in spinal cord injury

Background

It has recently been demonstrated that palmitoylethanolamide (PEA), an endogenous lipid amide belonging to the N-acylethanolamine family, exerts neuroprotection in central nervous system (CNS) pathologies. In recent studies, we have demonstrated that treatment with PEA significantly reduced inflammatory secondary events associated with spinal cord injury (SCI). Since oxidative stress is considered to play an important role in neuroinflammatory disorders, in the present work we studied a new composite, a formulation including PEA and the antioxidant compound luteolin (Lut), subjected to an ultramicronization process, co-ultraPEALut. We investigated the effect of co-ultraPEALut (in the respective fixed doses of 10:1 in mass) in both an ex vivo organotypic spinal cord culture model and an in vivo model of SCI.

Methods

For the organotypic cultures, spinal cords were prepared from mice at postnatal day 6 and were cut into transverse slices of 400 μm thickness to generate the lumbar organotypic slice cultures. After 7 days of culturing, the slices were mechanically injured onto the center of the slice and the co-ultraPEALut was applied at different concentrations (0.00009, 0.0009 and 0.009 g/l) 1 hour before damage. For in vivo studies, SCI was induced in mice through spinal cord compression by the application of vascular clips (force of 24 g) to the dura via a four-level T5 to T8 laminectomy, and co-ultraPEALut (1 mg/kg ip) was administered at 1 and 6 hours after SCI. At 24 hours after SCI, mice were sacrificed and the spinal cords were collected for further evaluation. Additional animals were treated similarly and sacrificed 10 days after SCI.

Results

Pretreatment with co-ultraPEALut significantly reduced cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression in a concentration-dependent manner, restored neuronal nitric oxide synthase (nNOS) expression at all three tested concentrations, and protected cells by cell death (MTT assay) in spinal cord organotypic cultures. Moreover, we demonstrated in vivo that co-ultraPEALut 1 mg/kg reduced the severity of trauma induced by compression and improved the motor activity evaluated at 10 days post-injury.

Conclusion

The present study demonstrates that the protective effect of PEA on SCI-associated neuroinflammation could be improved by co-ultramicronization with Lut possibly due to its antioxidant properties.

The persistent effects of maternal infection on the offspring's cognitive performance and rates of hippocampal neurogenesis

Accumulating evidence indicates that perinatal infection is a major cause of neonatal neurologic morbidity. Here we explored the effects of maternal infection on the offspring's cognitive performance and hippocampal neurogenesis. Pregnant rats were treated with Escherichia coli suspension and allowed to deliver. Proliferating cells in the hippocampus were examined at postnatal (P) 3, 7, 14, and 28 days and neuronal survival/differentiation was assessed at P28. Additionally, we examined the expressions of BDNF, TrkB and Akt. The cognitive performance of the offspring was assessed by the Morris water maze test. We found that maternal infection significantly impaired the offspring's spatial learning ability and spatial memory, thus could delay the cognitive performance development. Maternal infection significantly increased the number of proliferating cells in the offspring's hippocampus at postnatal 3, 7 and 14 days, accompanied by significantly increased expressions of BDNF, TrkB and p-Akt at postnatal 3 and 7 days. On postnatal 28 days, maternal infection did not significantly affect the neuronal and glial differentiation, nor any significant changes in the expression levels of BDNF and TrkB in the hippocampus. Our result suggests that the hippocampal neurogenesis level may increase during early postnatal period after maternal infection. Increase of BDNF/TrkB expression and Akt activity may be the contributing molecular mechanism.

Protective effect of ginkgolide B against acute spinal cord injury in rats and its correlation with the Jak/STAT signaling pathway

This study aimed to investigate the correlation between ginkgolide B (GB) and the JAK/STAT signaling pathway and to explore its regulating effect on secondary cell apoptosis following spinal cord injury (SCI), to elucidate the protective mechanism GB against acute SCI. Sprague-Dawley rats were randomly divided into a sham-operated group, an SCI group, an SCI + GB group, an SCI + methylprednisolone (MP) group, and an SCI + specific JAK inhibitor AG490 group. A rat model of acute SCI was established using the modified Allen's method. At 4 h, 12 h, 1 day, 3 days, 7 days and 14 days after injury, injured T10 spinal cord specimens were harvested. GB significantly increased inclined plane test scores and Basso, Beattie, and Bresnahan scale scores in SCI rats from postoperative day 3 to day 14. The effect was equal to that of the positive control drug, MP. Western blot analysis showed that JAK(2) was significantly phosphorylated from 4 h after SCI, peaked at 12 h and gradually decreased thereafter, accompanied by phosphorylation of STAT(3) with a similar time course. GB was shown to significantly inhibit the phosphorylation of JAK(2) and STAT(3) in rats with SCI. It significantly increased the ratio of B cell CLL/lymphoma-2 (Bcl-2)/Bcl-2-associated X protein (Bax) protein expression at 24 h, led to an obvious down-regulation of caspase-3 gene and protein expression at 3 days, and significantly decreased the cell apoptosis index at each time point after SCI. This effect was similar to that obtained with the JAK-specific inhibitor, AG490. Our experimental findings indicated that GB can protect rats against acute SCI, and that its underlying mechanism may be related to the inhibition of JAK/STAT signaling pathway activation, improvement of the Bcl-2/Bax ratio, decreased caspase-3 gene and protein expression and further inhibition of secondary cell apoptosis following SCI.

p53 controls neuronal death in the CA3 region of the newborn mouse hippocampus

It is important to determine the mechanisms controlling the number of neurons in the nervous system. Previously, we reported that neuronal activity plays a central role in controlling neuron number in the neonatal hippocampus of rodents. Neuronal survival requires sustained activation of the serine-threonine kinase Akt, which is initiated by neurotrophins and continued for several hours by neuronal activity and integrin signaling. Here, we focus on the CA3 region to show that neuronal apoptosis requires p53. As in wild-type animals, neuronal death occurs in the first postnatal week and ends by postnatal day (P)10 in p53(-/-) mice. During this period, the CA3 region of p53(-/-) mice contains significantly lower numbers of apoptotic cells, and at the end of the death period, it contains more neurons than the wild type. At P10, the p53(-/-) CA3 region contains a novel subpopulation of neurons with small soma size. These neurons show normal levels of tropomyosin receptor kinase receptor activation, but lower levels of activated Akt than the neurons with somata of normal size. These results suggest that p53 is the key downstream regulator of the novel survival-signaling pathway that regulates the number of CA3 neurons in the first 10 days of postnatal life.