α1‐Antitrypsin derived SP16 peptide demonstrates efficacy in rodent models of acute and neuropathic pain

Abstract

SP16 is an innovative peptide derived from the carboxyl‐terminus of α1‐Antitrypsin (AAT), corresponding to residues 364‐380, and contains recognition sequences for the low‐density lipoprotein receptor‐related protein‐1 (LRP1). LRP1 is an endocytic and cell‐signaling receptor that regulates inflammation. Deletion of Lrp1 in Schwann cells increases neuropathic pain; however, the role of LRP1 activation in nociceptive and neuropathic pain regulation remains unknown. Herein, we show that SP16 is bioactive in sensory neurons in vitro. Neurite length and regenerative gene expression were increased by SP16. In PC12 cells, SP16 activated Akt and ERK1/2 cell‐signaling in an LRP1‐dependent manner. When formalin was injected into mouse hind paws, to model inflammatory pain, SP16 dose‐dependently attenuated nociceptive pain behaviors in the early and late phases. In a second model of acute pain using capsaicin, SP16 significantly reduced paw licking in both male and female mice (p < .01) similarly to enzymatically inactive tissue plasminogen activator, a known LRP1 interactor. SP16 also prevented development of tactile allodynia after partial nerve ligation and this response was sustained for nine days (p < .01). Immunoblot analysis of the injured nerve revealed decreased CD11b (p < .01) and Toll‐like receptor‐4 (p < .005). In injured dorsal root ganglia SP16 reduced CD11b+ cells (p < .05) and GFAP (p < .005), indicating that inflammatory cell recruitment and satellite cell activation were inhibited. In conclusion, administration of SP16 blocked pain‐related responses in three distinct pain models, suggesting efficacy against acute nociceptive, inflammatory, and neuropathic pain. SP16 also attenuated innate immunity in the PNS. These studies identify SP16 as a potentially effective treatment for pain.

Binding and Activation of LRP1-Dependent Cell Signaling in Schwann Cells Using a Peptide Derived from the Hemopexin Domain of MMP-9

“…Of the four selected peptides, only peptide 2 activated Akt and ERK1/2 signaling in primary hSCs and bound to the LRP1 binding domains, CCR II and CCR IV, suggesting that this peptide is a true human LRP1 binder. Among these 4 peptides, only peptide 2 contains two somewhat proximal lysine residues that is consistent with critical lysine residues identified in the binding region of other LRP1 ligands , such as coagulation factor VIII, PAI-1, and more recently, SP16 . When lysine 111 was converted to an alanine, the level of binding to CCRII was reduced.…”

“…Only GST-PEX and peptide 2 pulled down the LRP1 CCR II and IV domains (Figure A). When we added RAP, a competitive antagonist to LRP1 routinely used to block binding of ligands to LRP1, , binding of GST-PEX was substantially inhibited (Figure B) but not peptide 2 . We attribute this finding to the small size of peptide 2 compared to GST-PEX, which may not be inhibited sterically by RAP for binding to LRP1 as previously observed with other protein LRP1 ligands.…”

Safety, Tolerability, and Effects of a Single Subcutaneous Administration of SP16 – a SERPIN-like, Small Peptide Agonist of the Low-Density Lipoprotein–like Receptor 1– on the Acute Inflammatory Response in Patients With ST-Segment Elevation Myocardial Infarction

“…11,12 Of note, SP16 is different from other antiinflammatory strategies being studied in STEMI (ie, anakinra) 16 because it is the first to exploit a natural signaling process that is anti-inflammatory as a receptor agonist for LRP1 9 and exhibits cellular and tissue repair as was shown in numerous disease models. 9,21 In a first-in-human phase 1 study of SP16 given to healthy volunteers, a single subcutaneous injection of SP16 up to 0.2 mg/kg (max dose of 12 mg) was well-tolerated and lacked any cardiac (or noncardiac) toxicities or biochemical effects on coagulation, platelet function, and liver enzymes. In line with these findings, the administration of SP16 was safe, well-tolerated, and not associated with any drug-related adverse events in the current phase 1B/2A study.…”

“…11,12 Of note, SP16 is different from other anti-inflammatory strategies being studied in STEMI (ie, anakinra) 16 because it is the first to exploit a natural signaling process that is anti-inflammatory as a receptor agonist for LRP1 9 and exhibits cellular and tissue repair as was shown in numerous disease models. 9,21…”

Axon‐derived PACSIN1 binds to the Schwann cell survival receptor, LRP1, and transactivates TrkC to promote gliatrophic activities

“…L3, L4, and L5 DRGs were then collected. DRGs and sciatic nerves were embedded in paraffin, and IHC studies were performed as previously described (Wang et al, 2022). Briefly, 1–5 μm thick DRG or nerve tissue sections were immunostained for PACSIN1.…”