A Novel Highly Sensitive Method for Measuring Inflammatory Neural-Derived APC Activity in Glial Cell Lines, Mouse Brain and Human CSF

Factor VII, EPCR, aPC Modulators: novel treatment for neuroinflammation

Background

Inflammation and coagulation are linked and pathogenic in neuroinflammatory diseases. Protease-activated receptor 1 (PAR1) can be activated both by thrombin, inducing increased inflammation, and activated protein C (aPC), inducing decreased inflammation. Modulation of the aPC-PAR1 pathway may prevent the neuroinflammation associated with PAR1 over-activation.

Methods

We synthesized a group of novel molecules based on the binding site of FVII/aPC to the endothelial protein C receptor (EPCR). These molecules modulate the FVII/aPC-EPCR pathway and are therefore named FEAMs—Factor VII, EPCR, aPC Modulators. We studied the molecular and behavioral effects of a selected FEAM in neuroinflammation models in-vitro and in-vivo.

Results

In a lipopolysaccharide (LPS) induced in-vitro model, neuroinflammation leads to increased thrombin activity compared to control (2.7 ± 0.11 and 2.23 ± 0.13 mU/ml, respectively, p = 0.01) and decreased aPC activity (0.57 ± 0.01 and 1.00 ± 0.02, respectively, p < 0.0001). In addition, increased phosphorylated extracellular regulated kinase (pERK) (0.99 ± 0.13, 1.39 ± 0.14, control and LPS, p < 0.04) and protein kinase B (pAKT) (1.00 ± 0.09, 2.83 ± 0.81, control and LPS, p < 0.0002) levels indicate PAR1 overactivation, which leads to increased tumor necrosis factor-alpha (TNF-α) level (1.00 ± 0.04, 1.35 ± 0.12, control and LPS, p = 0.02). In a minimal traumatic brain injury (mTBI) induced neuroinflammation in-vivo model in mice, increased thrombin activity, PAR1 activation, and TNF-α levels were measured. Additionally, significant memory impairment, as indicated by a lower recognition index in the Novel Object Recognition (NOR) test and Y-maze test (NOR: 0.19 ± 0.06, -0.07 ± 0.09, p = 0.03. Y-Maze: 0.50 ± 0.03, 0.23 ± 0.09, p = 0.02 control and mTBI, respectively), as well as hypersensitivity by hot-plate latency (16.6 ± 0.89, 12.8 ± 0.56 s, control and mTBI, p = 0.01), were seen. FEAM prevented most of the molecular and behavioral negative effects of neuroinflammation in-vitro and in-vivo, most likely through EPCR-PAR1 interactions.

Conclusion

FEAM is a promising tool to study neuroinflammation and a potential treatment for a variety of neuroinflammatory diseases.

Prolonged Systemic Inflammation Alters Muscarinic Long-Term Potentiation (mLTP) in the Hippocampus

The cholinergic system plays a fundamental role in learning and memory. Pharmacological activation of the muscarinic receptor M1R potentiates NMDA receptor activity and induces short-term potentiation at the synapses called muscarinic LTP, mLTP. Dysfunction of cholinergic transmission has been detected in the settings of cognitive impairment and dementia. Systemic inflammation as well as neuroinflammation has been shown to profoundly alter synaptic transmission and LTP. Indeed, intervention which is aimed at reducing neuroinflammatory changes in the brain has been associated with an improvement in cognitive functions. While cognitive impairment caused either by cholinergic dysfunction and/or by systemic inflammation suggests a possible connection between the two, so far whether systemic inflammation affects mLTP has not been extensively studied. In the present work, we explored whether an acute versus persistent systemic inflammation induced by LPS injections would differently affect the ability of hippocampal synapses to undergo mLTP. Interestingly, while a short exposure to LPS resulted in a transient deficit in mLTP expression, a longer exposure persistently impaired mLTP. We believe that these findings may be involved in cognitive dysfunctions following sepsis and possibly neuroinflammatory processes.

Markers for neural degeneration and regeneration: novel highly sensitive methods for the measurement of thrombin and activated protein C in human cerebrospinal fluid

Inflammation and coagulation are tightly interconnected in the pathophysiology of neuronal diseases. Thrombin, a pro-coagulant serine protease is associated with neurodegeneration and its indirect inhibitor, activated protein C (aPC), is considered neuroprotective. While levels of thrombin and aPC activity are readily measured in the blood, similar assays in the cerebrospinal fluid (CSF) have not been described. The aim of this study was to establish a specific and sensitive enzymatic assay to measure both thrombin and aPC activity in the CSF. CSF was collected from 14 patients with suspected normal pressure hydrocephalus served as a control group, while seven patients with central nervous system infections served as an acute neuro-inflammatory study group and one sample of CSF following traumatic lumbar puncture served as a positive control. Thrombin and aPC activities were measured by fluorescence released by specific proteolytic cleavage in the presence of endopeptidase and amino-peptidase inhibitors to ensure specificity. Specificity of the method was verified by thrombin and serine-protease inhibitors N-alpha-((2-naphthylsulfinyl)glycyl)-DL-p-amidinophenylalanylpiperidine and phenylmethanesulfonyl fluoride. Inhibition of thrombin activity by CSF samples and levels of specific thrombin inhibitors were also assessed. Thrombin and aPC activities were reliably measured and were significantly higher in the CSF of patients with central nervous system infections compared to normal pressure hydrocephalus controls, suggesting the involvement of these factors in neuro-inflammation. CSF thrombin activity levels in the presence of known thrombin concentration were high in patients with central nervous system infections, and low in normal pressure hydrocephalus patients. Quantification of endogenous thrombin inhibitors protease nexin 1, amyloid precursor protein and anti-thrombin III in CSF by western blot indicated a significant elevation of amyloid precursor protein in infectious CSF. In conclusion, this study describes a novel and sensitive assay aimed at the detection of thrombin and aPC activity in CSF. This method may be useful for measuring these factors that reflect degenerative and protective influences of coagulation on neurological disorders. The study procedure was approved by the Ethics Committee of the Chaim Sheba Medical Center (approval No. 4245-17-SMC) on October 18, 2018.