Translation of paclitaxel-induced peripheral neurotoxicity from mice to patients: the importance of model selection

Astrocytes in the rostral ventromedial medulla mediate the analgesic effect of electroacupuncture in a rodent model of chemotherapy-induced peripheral neuropathic pain

ABSTRACT

Chemotherapy-induced peripheral neuropathic pain aggravates cancer survivors' life burden. Electroacupuncture (EA) has exhibited promising analgesic effects on neuropathic pain in previous studies. We investigated whether EA was effective in a paclitaxel-induced neuropathic pain mouse model. We further explored the functional role of astrocytes in the rostral ventromedial medulla (RVM), a well-established pain modulation center, in the process of neuropathic pain as well as the analgesic effect of EA. We found that paclitaxel induced mechanical allodynia, astrocytic calcium signaling, and neuronal activation in the RVM and spinal cord, which could be suppressed by EA treatment. Electroacupuncture effectively alleviated paclitaxel-induced mechanical allodynia, and the effect was attenuated by the chemogenetic activation of astrocytes in the RVM. In addition, inhibiting astrocytic calcium activity by using either IP 3 R2 knockout (IP 3 R2 KO) mice or microinjection of AAV-mediated hPMCA2 w/b into the RVM to reduce non-IP 3 R2-dependent Ca 2+ signaling in astrocytes exhibited an analgesic effect on neuropathic pain, which mimicked the EA effect. The current study revealed the pivotal role of the RVM astrocytes in mediating the analgesic effects of EA on chemotherapy-induced peripheral neuropathic pain.

Electrophysiological characteristics of neuropathic pain model in mice and a technique to evaluate peripheral nerve damage in the sciatic nerve

Background

Experimental neuropathic pain (NP) models were developed from peripheral injuries and are widely used for pain research. However, previously published methods and outcomes in the evaluation of sciatic nerve dysfunction vary widely across each report. In this study, we established the electrophysiological analysis of sensory nerve action potentials (SNAPs) and compound motor action potentials (CMAPs) as objective methods for evaluating sciatic nerve dysfunction and revealed the electrophysiological characteristics of NP mice models.

Methods

We used male C57BL/6 J mice, C57BLKS/J lar- + Leprdb/+Leprdb (db/db) mice, and mouse models of paclitaxel-induced NP and spared nerve injury (SNI) surgery (10 mice in each group). For nerve conduction studies, we used evoked potential/electromyography apparatuses and bipolar electrodes as stimulating and recording electrodes for SNAPs and CMAPs. SNAPs were recorded from the sciatic nerve. For the distal motor latency and CMAPs amplitude measurements, we placed the cathode of the recording electrode on the gastrocnemius muscle.

Results

In electrophysiological assessments, the SNI model showed the most severe sensory disturbance in SNAP with allodynia in the sciatic nerve. The db/db model showed moderate sensory disturbance with allodynia, whereas the paclitaxel model showed slight sensory disturbance but also with allodynia. Only the SNI model showed significantly lower amplitudes of CMAPs than those of normal mice, whereas the paclitaxel and db/db models showed sensory disturbance but no loss of motor function.

Conclusions

We focused on the detailed methodology of electrophysiological assessment in experimental NP models. Our method of electrophysiological analysis of SNAPs and CMAPs of the sciatic nerve was well reflected in the pain withdrawal tests performed in each NP model and may be useful for future research of NP in experimental NP models.

Ameliorative Potential of Carvedilol Versus Platelet-Rich Plasma Against Paclitaxel-Induced Femoral Neuropathy in Wistar Rats: A Light and Electron Microscopic Study

Paclitaxel, a chemotherapeutic drug, induces sensorimotor peripheral neuropathy. Carvedilol, a nonselective β-adrenoreceptor blocker, has been shown to exert antioxidant activity. Platelet-rich plasma (PRP) has supra-physiological levels of growth factors (GFs), enhances biosynthesis of antioxidant enzymes, and suppresses oxidative stress. This study compared the ameliorative effects of carvedilol and PRP on paclitaxel-induced femoral neuropathy. Eighty-eight adult male albino rats were equally randomized into four groups: group I served as the control; group II received paclitaxel (16 mg/kg intraperitoneally, weekly); group III received carvedilol (10 mg/kg daily, orally) concomitant with paclitaxel; and group IV received PRP (0.5 mL/kg subcutaneously, twice weekly) concomitant with paclitaxel. After 5 weeks, femoral nerve conduction velocity was measured, and blood samples were collected to assess catalase and superoxide dismutase levels. All animals were sacrificed, and gene expression of miR-21 was quantified. Tissue sections were stained with hematoxylin and eosin and toluidine blue. Then, the ultrathin sections were examined by transmission electron microscopy. Both carvedilol and PRP reversed paclitaxel-induced changes in the peripheral nerve, but PRP demonstrated a stronger antioxidant effect and a more pronounced presence of GFs, as evidenced by electron microscopy. PRP may represent a promising therapeutic approach for paclitaxel-induced neuropathy.

Ion Channel and Transporter Involvement in Chemotherapy-Induced Peripheral Neurotoxicity

The peripheral nervous system can encounter alterations due to exposure to some of the most commonly used anticancer drugs (platinum drugs, taxanes, vinca alkaloids, proteasome inhibitors, thalidomide), the so-called chemotherapy-induced peripheral neurotoxicity (CIPN). CIPN can be long-lasting or even permanent, and it is detrimental for the quality of life of cancer survivors, being associated with persistent disturbances such as sensory loss and neuropathic pain at limb extremities due to a mostly sensory axonal polyneuropathy/neuronopathy. In the state of the art, there is no efficacious preventive/curative treatment for this condition. Among the reasons for this unmet clinical and scientific need, there is an uncomplete knowledge of the pathogenetic mechanisms. Ion channels and transporters are pivotal elements in both the central and peripheral nervous system, and there is a growing body of literature suggesting that they might play a role in CIPN development. In this review, we first describe the biophysical properties of these targets and then report existing data for the involvement of ion channels and transporters in CIPN, thus paving the way for new approaches/druggable targets to cure and/or prevent CIPN.