Peripheral Administration of the Selective Inhibitor of Soluble Tumor Necrosis Factor (TNF) XPro®1595 Attenuates Nigral Cell Loss and Glial Activation in 6-OHDA Hemiparkinsonian Rats

Abstract

Background: Parkinson's disease (PD) is a complex multi-system age-related neurodegenerative disorder. Targeting the ongoing neuroinflammation in PD patients is one strategy postulated to slow down or halt disease progression. Proof-of-concept studies from our group demonstrated that selective inhibition of soluble Tumor Necrosis Factor (solTNF) by intranigral delivery of dominant negative TNF (DN-TNF) inhibitors reduced neuroinflammation and nigral dopamine (DA) neuron loss in endotoxin and neurotoxin rat models of nigral degeneration. Objective: As a next step toward human clinical trials, we aimed to determine the extent to which peripherally administered DN-TNF inhibitor XPro ® 1595 could: i) cross the blood-brain-barrier in therapeutically relevant concentrations, ii) attenuate neuroinflammation (microglia and astrocyte), and iii) mitigate loss of nigral DA neurons in rats receiving a unilateral 6-hydroxydopamine (6-OHDA) striatal lesion. Methods: Rats received unilateral 6-OHDA (20 g into the right striatum). Three or 14 days after lesion, rats were dosed with XPro ® 1595 (10 mg/kg in saline, subcutaneous) every third day for 35 days. Forelimb asymmetry was used to assess motor deficits after the lesion; brains were harvested 35 days after the lesion for analysis of XPro ® 1595 levels, glial activation and nigral DA neuron number. Results: Peripheral subcutaneous dosing of XPro ® 1595 achieved plasma levels of 1-8 microgram/mL and CSF levels of 1-6 ng/mL depending on the time the rats were killed after final XPro ® 1595 injection. Irrespective of start date, XPro ® 1595 significantly reduced microglia and astrocyte number in SNpc whereas loss of nigral DA neurons was attenuated when drug was started 3, but not 14 days after the 6-OHDA lesion. Conclusions: Our data suggest that systemically administered XPro ® 1595 may have disease-modifying potential in PD patients where inflammation is part of their pathology.

Hippocampal TNFα Signaling Contributes to Seizure Generation in an Infection-Induced Mouse Model of Limbic Epilepsy

“…In previous studies, the concentration of XPro1595 in CSF and plasma were found to be 1–6 ng/ml and 1–8 µg/ml, respectively, after subcutaneous treatment of rats with 10 mg/kg XPro1595 (Barnum et al, 2014). A 10-fold higher level of XPro1595, as used here, would be expected to exchange 99% of endogenous sTNFα (Steed et al, 2003).…”

“…The concentration of XPro1595 in the CSF (1–6 ng/ml) has been found to be 1000-fold reduced compared with that in the plasma (1–8 µg/ml) from rats after 2–3 d of treatment with XPro1595 (10 mg/kg s.c.; Barnum et al, 2014). Furthermore, as in the model of SCI, in which acute inflammatory response occurs rapidly in the CNS, the protein levels of TNFα and other inflammatory cytokines increase rapidly in the hippocampus after TMEV infection.…”

Peripheral administration of the soluble TNF inhibitor XPro1595 modifies brain immune cell profiles, decreases beta-amyloid plaque load, and rescues impaired long-term potentiation in 5xFAD mice

“…Further investigation may reveal that modulating these multiple mechanisms of sTNF may be contributing to the overall effects on LTP and immune cell trafficking. Our group has shown that peripherally administered XPro1595 gets across the BBB and is able to sequester the picomolar levels of sTNF within the brain (Barnum et al, 2014); however, a recent clinical study with a non-BBB crossing TNF inhibitor (etanercept), implicates a TNF-dependent peripheral mechanisms in the cognitive decline associated with AD pathogenesis (Butchart et al, 2015). Together, these data suggest that TNF can have both direct effects on synaptic physiology as well as indirect effects on peripheral cytokines and immune cell traffic to the CNS and brain resident immune cells and thus, targeting sTNF centrally and peripherally may afford added advantage to improve functional outcomes in patients with AD.…”

“…XPro1595 is a PEG-ylated human TNF variant devoid of TNF receptor-binding activity that forms heterotrimers with native sTNF (but not membrane-bound TNF), thereby sequestering sTNF away from TNF receptors (Steed et al, 2003; Barnum et al, 2014). To assess the role of sTNF in AD-like pathology and immune cell trafficking to the CNS, Tg female mice were divide into two cohorts each with two treatment groups.…”

“…Mice received either subcutaneous (s.c.) saline vehicle control or s.c. XPro1595 (10 mg/kg) twice weekly for two months. This dose was selected on the basis of PK/PD studies and its efficacy in reducing dopaminergic neuron loss and glial activation in a rat model of nigral degeneration (Barnum et al, 2014). When administered peripherally, XPro1595 is detectable in the brain (1 and 6 ng/mL of is detectable in the brain (Supp Fig.…”