SARS-CoV-2 Exacerbates COVID-19 Pathology Through Activation of the Complement and Kinin Systems.

Infection with SARS-CoV-2 triggers the simultaneous activation of innate inflammatory pathways including the complement system and the kallikrein-kinin system (KKS) generating in the process potent vasoactive peptides that contribute to severe acute respiratory syndrome (SARS) and multi-organ failure. The genome of SARS-CoV-2 encodes four major structural proteins - the spike (S) protein, nucleocapsid (N) protein, membrane (M) protein, and the envelope (E) protein. However, the role of these proteins in either binding to or activation of the complement system and/or the KKS is still incompletely understood. In these studies, we used: solid phase ELISA, hemolytic assay and surface plasmon resonance (SPR) techniques to examine if recombinant proteins corresponding to S1, N, M and E: (a) bind to C1q, gC1qR, FXII and high molecular weight kininogen (HK), and (b) activate complement and/or the KKS. Our data show that the viral proteins: (a) bind C1q and activate the classical pathway of complement, (b) bind FXII and HK, and activate the KKS in normal human plasma to generate bradykinin and (c) bind to gC1qR, the receptor for the globular heads of C1q (gC1q) which in turn could serve as a platform for the activation of both the complement system and KKS. Collectively, our data indicate that the SARS-CoV-2 viral particle can independently activate major innate inflammatory pathways for maximal damage and efficiency. Therefore, if efficient therapeutic modalities for the treatment of COVID-19 are to be designed, a strategy that includes blockade of the four major structural proteins may provide the best option.

A novel, minimally invasive technique to establish the animal model of spinal cord injury.

BACKGROUND: Spinal cord injury (SCI) is a traumatic disease that is associated with high morbidity, disability, and mortality worldwide. The animal spinal cord contusion model is similar to clinical SCI; therefore, this model is often used to study the pathophysiological changes and treatment strategies for humans after SCI. The present study aimed to introduce a novel, minimally invasive technique to establish an SCI model, and to evaluate its advantages compared with conventional methods. METHODS: Incision length, blood loss, length of time, and model success rate during the operation were recorded. Postoperative hematuria, incision hematoma, scoliosis [detected by micro computed tomography (Micro-CT)] and mortality were analyzed to evaluate surgical complications. The visual observation of the tissue was used to compare the effect of laminectomy by 2 methods on the scar hyperplasia at the injured site. Basso-Beattie-Bresnahan (BBB) score and catwalk automated quantitative gait analysis were conducted to measure behavioral function recovery. To evaluate the nerve function recovery of rats postoperatively, somatosensory evoked potential (SEP) and motor evoked potential (MEP) were studied by electrophysiological analyses. RESULTS: The results of operation-related parameters of the two models (conventional surgery group vs. minimally invasive surgery group) were as follows: surgical incision length: 23.58±1.58 versus 12.67±1.50 mm (P<0.05), blood loss: 3.96±1.05 versus 1.34±0.87 mL (P<0.05), and total operative time: 12.67±1.78 versus 10.33±1.92 min (P<0.05). In addition, the success rate of the 2 models was 100%. Surgical complications (conventional surgery group vs. minimally invasive surgery group) were as follows: hematuria: 25% versus 8.3%, kyphosis: 25% versus 0%, incision hematoma: 30% versus 9%, and mortality: 25% versus 8.3%. Micro-CT indicated severe scoliosis in the conventional surgery group. Gross tissue results showed that the conventional surgery group had more severe fibrous scar hyperplasia. The results of the BBB scores, catwalk automated quantitative gait analysis, and electrophysiology showed that the difference between the two groups was statistically significant in terms of behavioral recovery and neuroelectrophysiology. CONCLUSIONS: The minimally invasive technique has the advantages of small incision and reduced tissue damage and surgical complications, and may be used as an alternative spinal cord contusion method.

Neurotropin exerts neuroprotective effects after spinal cord injury by inhibiting apoptosis and modulating cytokines.

BACKGROUND/OBJECTIVE: Spinal cord injury (SCI) severely and irreversibly damages the central nervous system. Neurotropin (NTP), a nonprotein extract obtained from inflamed rabbit skin inoculated with vaccinia virus, is a drug that has been used for more than sixty years to alleviate neuropathic pain. It also reportedly exerts a neuroprotective role in peripheral nerves and in response to various central nervous system diseases, such as brain injury and Alzheimer disease. However, whether NTP promotes SCI recovery remains unknown. This study evaluated NTP's effects after SCI and explored its underlying mechanisms in a rat contusion model of SCI. METHOD: NTP was intraperitoneally administered to adult female Wistar rats subjected to contusion-induced SCI. Functional recovery was evaluated with behavioural scores and electrophysiological examinations. Tissue recovery was assessed with magnetic resonance imaging as well as histological staining with haematoxylin and eosin and Luxol Fast Blue. Neuronal survival and gliosis were observed after NeuN and glial fibrillary acidic protein immunofluorescence. Levels of apoptosis were demonstrated with TdT-mediated dUTP nick-end labeling (TUNEL) staining, Caspase-3 and B-cell lymphoma-2 (Bcl-2) Western blot, and Annexin V/propidium iodide flow cytometry. A protein antibody chip analysis was performed to evaluate the expression levels of 67 rat cytokines. RESULTS: NTP treatment improved the hindlimb locomotor recovery of the injured animals as well as their electrophysiological outcomes after SCI. A dosage of 50 NTP units/kg was found to optimize the efficacy of NTP. Magnetic resonance imaging revealed that lesion sizes decreased after NTP treatment. The haematoxylin and eosin and Luxol Fast Blue staining showed significant increases in the amount of spared tissue. The NeuN and glial fibrillary acidic protein immunofluorescence revealed that NTP treatment increased neuronal survival and reduced gliosis in tissue samples obtained from the lesion's epicentre. That NTP inhibited apoptosis was confirmed by the decreased number of TUNEL-positive cells, level of Caspase-3 expression, and number of Annexin V/propidium iodide-positive cells, as well as the increased level of Bcl-2 expression. The protein array analysis identified 28 differentially expressed proteins in the NTP group, and the gene ontology (GO) analysis showed that the enriched differentially expressed proteins implicate janus kinase-signal transducer and activator of transcription (JAK-STAT) signalling pathways. The expression levels of proinflammatory cytokines such as interleukin 6, thymus chemokine-1(TCK-1), and lipopolysaccharide-induced CXC chemokine (LIX) decreased after NTP treatment, whereas the levels of prorepair cytokine hepatocyte growth factor and adiponectin increased. CONCLUSION: Our research provides evidence that NTP can improve functional outcomes and alleviate secondary injury after SCI by inhibiting apoptosis and modulating cytokines. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The multicomponent NTP might have broad target spectra in SCI pathophysiology and halt the secondary injury cascade. As a safe drug that features sixty years of clinical use as an analgesic, translating this demonstrated efficacy of NTP to addressing SCI in human patients may potentially be accelerated.

Circular RNA derived from TIMP2 functions as a competitive endogenous RNA and regulates intervertebral disc degeneration by targeting miR­185­5p and matrix metalloproteinase 2.

Intervertebral disc degeneration (IDD) is an important cause of lower back pain, although the underlying mechanisms remain poorly understood. The present study aimed to examine the role of a circular RNA derived from tissue inhibitor of metallopeptidases 2 (circ­TIMP2) in degenerative nucleus pulposus (NP) tissues, and to validate its function in cultured human NP cells. Overexpression of miR­185­5p in NP cells markedly inhibited the enhanced extracellular matrix (ECM) catabolism induced by tumor necrosis factor­α (TNF­α) and interleukin­1ß (IL­1ß) treatment. Bioinformatics analysis demonstrated that matrix metalloproteinase 2 (MMP2) was a potential target of miR­185­5p. MMP2 protein expression levels were increased following treatment with TNF­α and IL­1ß in NP cells compared with those in untreated cells, and this effect was attenuated by transfection with miR­185­5p. Compared with normal NP tissues, IDD samples exhibited higher circ­TIMP2 expression levels. In addition, overexpression of circ­TIMP2 promoted ECM catabolism and suppressed ECM anabolism. Furthermore, circ­TIMP2 sequestered miR­185­5p, which may potentially upregulate the target genes associated with ECM degradation. In conclusion, the results of the present study revealed that circ­TIMP2 promoted TNF­α­ and IL­1ß­induced NP cell imbalance between ECM anabolism and catabolism via miR­185­5p­MMP2 signaling. These findings provide a potential therapeutic option for the treatment of IDD.

Circular RNA GRB10 as a competitive endogenous RNA regulating nucleus pulposus cells death in degenerative intervertebral disk.

Intervertebral disc degeneration (IDD) is an important factor leading to low back pain, but the underlying mechanisms remain poorly understood. Compared with normal nucleus pulposus (NP) tissues, the expression of circ-GRB10 was downregulated in IDD. Furthermore, overexpression of circ-GRB10 inhibited NP cell apoptosis. circ-GRB10 could sequester miR-328-5p, which could potentially lead to the upregulation of target genes related to cell proliferation via the ErbB pathway. In conclusion, the present study revealed that circ-GRB10/miR-328-5p/ERBB2 signaling pathway is involved in IDD development, suggesting that circ-GRB10 might be a novel therapeutic target for IDD.

Mechanisms underlying the promotion of functional recovery by deferoxamine after spinal cord injury in rats.

Deferoxamine, a clinically safe drug used for treating iron overload, also repairs spinal cord injury although the mechanism for this action remains unknown. Here, we determined whether deferoxamine was therapeutic in a rat model of spinal cord injury and explored potential mechanisms for this effect. Spinal cord injury was induced by impacting the spinal cord at the thoracic T10 vertebra level. One group of injured rats received deferoxamine, a second injured group received saline, and a third group was sham operated. Both 2 days and 2 weeks after spinal cord injury, total iron ion levels and protein expression levels of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1ß and the pro-apoptotic protein caspase-3 in the spinal cords of the injured deferoxamine-treated rats were significantly lower than those in the injured saline-treated group. The percentage of the area positive for glial fibrillary acidic protein immunoreactivity and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were also significantly decreased both 2 days and 2 weeks post injury, while the number of NeuN-positive cells and the percentage of the area positive for the oligodendrocyte marker CNPase were increased in the injured deferoxamine-treated rats. At 14-56 days post injury, hind limb motor function in the deferoxamine-treated rats was superior to that in the saline-treated rats. These results suggest that deferoxamine decreases total iron ion, tumor necrosis factor-α, interleukin-1ß, and caspase-3 expression levels after spinal cord injury and inhibits apoptosis and glial scar formation to promote motor function recovery.

[Neuroprotective effects and mechanism of saikosaponin A on acute spinal cord injury in rats].

Objective: To investigate the effect of saikosaponin a (SSa) on the levels of immune inflammation in rats with acute spinal cord injury and its possible mechanism. Methods: Seventy-two Sprague Dawley rats (weighing, 220-250 g) were randomly divided into sham operation group (group A), spinal cord injury group (group B), and SSa treatment group (group C) respectively, 24 rats in each group. The spinal cord injury model was induced by using the Allen's method in groups B and C; the spinous process and vertebral plate at both sides were cut off by lamina excision to expose the spinal cord in group A. The rats were given intraperitoneal injection of 10 mg/kg SSa in group C and equal volume of normal saline in group B at immediate after injury. The spinal cord tissue was harvested from 18 rats of each group at 24 hours after operation to measure the levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) by ELISA, to detect the expressions of nuclear factor κB (NF-κB) P65, NF-κB P-P65, and aquaporin 4 (AQP4) by Western blot and to observe the morphology of spinal cord by HE staining. The motor function of the lower limbs was evaluated by BBB score and tiltboard experiment in 6 rats at 1, 3, 7, 14, 21, and 28 days after injury. Results: The BBB score and tiltboard experiment maximum angle were significantly higher in group A than groups B and C at each time point ( P<0.05) and in group C than group B at 14, 21, and 28 days after operation ( P<0.05). ELISA test showed that the concentrations of TNF-α and IL-6 were significantly lower in group A than groups B and C, and in group C than group B ( P<0.05). Western blot results showed that the protein expression levels of NF-κB P65, NF-κB P-P65, and AQP4 were significantly lower in group A than groups B and C, and in group C than group B ( P<0.05). HE staining demonstrated normal neurons of the spinal cord and no obvious lesion in group A; neuronal cells were observed in the injured area of group B, with hemorrhage, neutrophil infiltration, and nerve cell edema in the injured area; the neuronal cells were visible in the spinal cord of group C, with microglia mild hyperplasia, and the pathological changes were improved when compared with group B. Conclusion: SSa has neuroprotective effects on acute spinal cord injury in rats by inhibiting NF-κB signaling pathway and AQP4 protein expression and reducing inflammation response and edema.