Bayer School of Natural and Environmental Sciences
Dr. John A. Pollock
Dr. Jelena M. Janjic
Dr. Benedict J. Kolber
Dr. Nicholas F. Fitz
Inflammation, Nanomedicine, Neuropathic pain, Chronic pain, Macrophage, Mast cell
We explored the immune neuropathology underlying multi-day relief from neuropathic pain in a rat model initiated at the sciatic nerve by using a nanoemulsion-based nanomedicine as a biological probe. The nanomedicine is theranostic: both therapeutic (containing celecoxib drug) and diagnostic (containing near-infrared fluorescent (NIRF) dye) and is small enough to be phagocytosed by circulating monocytes. A model of neuropathic pain is initiated by tying four 1mm spaced knots around the sciatic nerve with chromic gut suture, which results in neuroinflammation, and a resultant pain-like behavior manifests. We show that pain-like behavior reaches a plateau of maximum hypersensitivity 8 days post-surgery, and is the rationale for intravenous delivery at this time-point. Pain relief is evident within 24 hours, lasting approximately 6 days. The ipsilateral sciatic nerve and associated L4 and L5 dorsal root ganglia (DRG) tissue of both nanomedicine and control (nanoemulsion without drug) treated animals was investigated by immunofluorescence and confocal microscopy at the peak of pain relief (day 12 post-surgery), and when pain-like hypersensitivity returns (day 18 post-surgery). At day 12, a significant reduction of infiltrating macrophages, mast cells and mast cell degranulation was observed at the sciatic nerve following treatment. In the DRG, there was no effect of treatment at both day 12 and day 18 on the numbers of macrophages and mast cells. Conversely, at the DRG, there is a significant increase in macrophage infiltration and mast cell degranulation at day 18. The treatment effect on immune pathology in the sciatic nerve was investigated further by assessing the expression of macrophage cyclooxygenase-2 (COX-2)—the drug target--and extracellular prostaglandin E2 (PGE2), as well as the proportion of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages. At day 12, there is a significant reduction of COX-2 positive macrophages, extracellular PGE2, and a striking reversal of macrophage polarity. At day 18, these measures revert to levels observed in control-treated animals. Here we present a new paradigm of immune neuropathology research, by employing a nanomedicine to target a mechanism of neuropathic pain—resulting in long-lasting pain relief--whilst revealing novel immune pathology at the injured nerve and associated DRG.
The pathology of pain relief that these studies reveal, highlights a crucial concept: that a single nanomedicine dose targeted to general peripheral neuroinflammation, may not be sufficient—that a treatment plan could be modified to firstly include additional treatment points, and secondly target the associated DRG in order to dampen the inflammation and pain signaling emanating there.
Saleem, M. (2019). Nanomedicine-driven neuropathic pain relief in rat model is associated with macrophage polarity and mast cell activation (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/1854
Saleem, M., Stevens, A. M., Deal, B., Liu, L., Janjic, J., Pollock, J. A. A New Best Practice for Validating Tail Vein Injections in Rat with Near-infrared-Labeled Agents. J. Vis. Exp. (146), e59295, doi:10.3791/59295 (2019).
Janjic, J., Vasudeva, K., Saleem, M. et al. Low-dose NSAIDs reduce pain via macrophage targeted nanoemulsion delivery to neuroinflammation of the sciatic nerve in rat. Journal of Neuroimmunology 318, 72-79 (2018) doi:10.1016/j.jneuroim.2018.02.010
Saleem, M., Deal, B., Nehl, E. et al. Nanomedicine-driven neuropathic pain relief in a rat model is associated with macrophage polarity and mast cell activation. acta neuropathol commun 7, 108 (2019) doi:10.1186/s40478-019-0762-y