Drug-induced dysimmune demyelinating neuropathies

Lysosomal dysfunction in Schwann cells is involved in bortezomib-induced peripheral neurotoxicity

Bortezomib (BTZ) is a proteasome inhibitor serves as a first-line drug for multiple myeloma treatment. BTZ-induced peripheral neuropathy (BIPN) is the most common adverse effect of BTZ with an incidence as high as 40-60%. However, the pathological mechanisms underlying BIPN remain largely unclear. BTZ leads to dramatic Schwann cell demyelination in sciatic nerves. Previous studies implied that myelin debris was predominantly degraded via autophagy-lysosome pathway in Schwann cells. However, the association of autophagy with BIPN has not been made. Mice were treated with BTZ (2 mg/kg, i.v.) on Day1 and Day4 each week for continuous 4 weeks. BTZ-treated mice showed enhanced mechanical hyperalgesia, decreased tail nerve conduction and sciatic nerve demyelination. Unexpectedly, BTZ led to the accumulation of autophagic vesicles, LC3-II and p62 in the sciatic nerve. Moreover, BTZ blocked autophagic flux in RSC96 Schwann cells as determined by mcherry-GFP-LC3 assay, suggesting BTZ may impair lysosomal function rather than inducing autophagy in Schwann cells. BTZ significantly reduced the lysosomal activity in Schwann cells as determined by reduced LysoTracker Red and DQ-Red-BSA staining and increased the level of immature Cathepsin B (CTSB). Remarkably, lysosomal activators PP242 and Torin1, significantly reversed the blockage of autophagic flux by BTZ. We further verified that Torin1 rescued the demyelination, nerve conduction and reduced the mechanical hyperalgesia in BIPN mice. Additionally, Torin1 did not compromise the efficacy of BTZ in suppressing multiple myeloma RPMI8226 cell. Taken together, we identified that lysosomal dysfunction in Schwann cells caused by BTZ is involved in the BIPN pathology. Improved lysosomal function in Schwann cells can be a promising strategy for BIPN treatment.

Medikamentös-induzierte Polyneuropathien jenseits von Chemotherapeutika und Antiinfektiva

Zahlreiche in der klinischen Routine eingesetzte Wirkstoffe jenseits von Chemotherapeutika und Antiinfektiva können eine Polyneuropathie verstärken oder hervorrufen. Kenntnis darüber, welche Medikamente mit Polyneuropathien assoziiert sind sowie über Risikofaktoren seitens der Patienten können die Häufigkeit reduzieren. Bei entsprechendem Risiko sollten alternative Präparate eingesetzt oder die Indikation zur Therapie generell überdacht werden.

Medikamentös-induzierte Polyneuropathien durch Chemotherapeutika und Antiinfektiva

Polyneuropathien können durch zahlreiche Wirkstoffe hervorgerufen oder aggraviert werden. Insbesondere die Chemotherapeutika-induzierte Polyneuropathie (CIPN) ist im Alltag von hoher Relevanz. Jedoch kann auch der Einsatz von Antiinfektiva zu neuropathischen Beschwerden führen. Im Folgenden soll ein Überblick über die wichtigsten mit Polyneuropathien assoziierten Wirkstoffe der Substanzklassen sowie die klinischen Charakteristika gegeben werden.

Grundlagen medikamentös-induzierter Polyneuropathien

Zahlreiche Wirkstoffe können mit dem erstmaligen Auftreten oder dem Fortschreiten neuropathischer Symptome in Verbindung gebracht werden. Insbesondere im Kontext der modernen Polypharmazie kommt medikamentös-induzierten Polyneuropathien eine besondere Bedeutung zu. Die Schädigungsmechanismen und individuellen Risikofaktoren sind vielfältig. In den meisten Fällen resultiert eine längenabhängige, axonale Polyneuropathie mit vorwiegend sensiblen Symptomen. Grundlegende Kenntnisse darüber, welche Arzneimittel mit dem Auftreten einer Polyneuropathie assoziiert sind, können dazu beitragen, das Auftreten dieser Nebenwirkung frühzeitig zu erkennen. Die Verordnung entsprechender Medikamente sollte vermieden werden, wenn das Risiko für den einzelnen Patienten als zu hoch eingeschätzt wird. Unter Therapie sind regelmäßige Kontrolluntersuchungen nötig, um bei neuauftretenden oder zunehmenden Symptomen die Therapie so früh wie möglich anpassen oder absetzen zu können. Die Prognose ist dann meist gut.

A case of spinal nerve neurotoxicity with ropivacaine after combined spinal and epidural anesthesia

Background

Neurotoxicity caused by a local anesthetic after regional anesthesia is a rare but serious problem for anesthesiologists. It is difficult to diagnose neurotoxicity from anesthetics because of the large number of possible diagnoses. In this case report, careful monitoring by neurological examinations helped to diagnose local neurotoxicity caused after epidural anesthesia.

Case description

A 41-year-old pregnant woman who underwent emergency cesarean delivery under combined spinal-epidural anesthesia suffered left leg paralysis after surgery. Multiple neurological examinations (e.g., electromyography, nerve conduction study) revealed that the paralysis was induced by the neurotoxicity of ropivacaine. The neurological examinations were also useful to monitor the recovery process.

Conclusions

This is the first clinical case report that describes the diagnosis of and recovery from local anesthesia-induced neurotoxicity monitored by electromyography and nerve conduction study. Neurological disorders caused by regional anesthetics should be carefully examined and diagnosed using these neurological examinations.

The molecular and cellular insight into the toxicology of bortezomib-induced peripheral neuropathy

The proteasome inhibitor bortezomib (BTZ) is a first-line antitumor drug, mainly used for multiple myeloma treatment. However, BTZ shows prominent toxicity in the peripheral nervous system, termed BTZ-induced peripheral neuropathy (BIPN). BIPN is characterized by neuropathic pain, resulting in a dose reduction or even treatment withdrawal. To date, the pathological mechanism of BIPN has not been elucidated. There is still no effective strategy to prevent or treat BIPN. This review summarizes the pathological mechanisms of BIPN, which involves the pathological changes of Schwann cells, neurons, astrocytes and macrophages. A better knowledge of the pathological mechanisms of BIPN would provide new ideas for therapeutic interventions of BIPN patients.

Demyelinating Neuropathy in a Patient Treated With Revusiran for Transthyretin (Thr60Ala) Amyloidosis

Transthyretin amyloidosis patients develop length-dependent peripheral neuropathy, autonomic dysfunction, and restrictive cardiomyopathy associated with deposition of amyloid fibrils in these tissues. Despite advances in management over the past decade, this disorder causes profound debilitation and ultimately proves fatal. In this report, we describe a man with late-onset cardiac amyloidosis due to a transthyretin Thr60Ala mutation who was treated with an investigational RNAi therapeutic, revusiran, which targets hepatic transthyretin production. Sixteen months into treatment, he developed bilateral lower-extremity weakness and numbness, worsening balance, difficulty manipulating objects with his hands, and finger numbness. Nerve conduction studies were consistent with multifocal demyelinating neuropathy. Intravenous immunoglobulin therapy improved sensation in his hands and feet, and improved hand dexterity. A sural nerve biopsy demonstrated demyelination with substantial axonal loss in the absence of histologically detectable endoneurial amyloid deposition. This case expands the clinicopathologic spectrum of transthyretin amyloidosis and may represent complex disease and treatment effects.

Autoimmune Neuromuscular Diseases Induced by Immunomodulating Drugs

Immunomodulating drugs are widely used in autoimmune, transplant, and cancer patients. However, these drugs are associated with various autoimmune neuromuscular diseases such as demyelinating polyneuropathy, myasthenia gravis, and myositis. Early recognition of these complications and immediately terminating these drugs are very essential since some are life-threatening conditions. This review provides a general overview of drug-induced autoimmunity and autoimmune neuromuscular diseases associated with tumor necrosis factor alpha (TNF-α) antagonists, immune checkpoint inhibitors, and interferon (IFN) type 1 (IFN-β and IFN-α).

Toxic and drug-induced peripheral neuropathies: updates on causes, mechanisms and management

PURPOSE OF REVIEW

This review discusses publications highlighting current research on toxic, chemotherapy-induced peripheral neuropathies (CIPNs), and drug-induced peripheral neuropathies (DIPNs).

RECENT FINDINGS

The emphasis in clinical studies is on the early detection and grading of peripheral neuropathies, whereas recent studies in animal models have given insights into molecular mechanisms, with the discovery of novel neuronal, axonal, and Schwann cell targets. Some substances trigger inflammatory changes in the peripheral nerves. Pharmacogenetic techniques are underway to identify genes that may help to predict individuals at higher risk of developing DIPNs. Several papers have been published on chemoprotectants; however, to date, this approach has not been shown effective in clinical trials.

SUMMARY

Both length and nonlength-dependent neuropathies are encountered, including small-fiber involvement. The introduction of new diagnostic techniques, such as excitability studies, skin laser Doppler flowmetry, and pharmacogenetics, holds promise for early detection and to elucidate underlying mechanisms. New approaches to improve functions and quality of life in CIPN patients are discussed. Apart from developing less neurotoxic anticancer therapies, there is still hope to identify chemoprotective agents (erythropoietin and substances involved in the endocannabinoid system are promising) able to prevent or correct painful CIPNs.

Neurologic complications of chemotherapy and other newer and experimental approaches

Neurologic complications of conventional cytototxic agents as well as those from monoclonal antibodies and targeted therapies are increasingly observed in patients with cancer. The major categories are represented by alkylating agents (platinum compounds, ifosfamide, procarbazine, thiotepa), mitotic spindle inhibitors (vinca alkaloids, taxanes, etoposide, teniposide), proteasome inhibitors (bortezomib), antibiotics, antimetabolites, thalidomide, lenalidomide, topoisomerase inhibitors, interferon-α, hormones, bevacizumab, trastuzumab, and small tyrosine kinase inhibitors. Peripheral neuropathy is a common adverse effect of a number of chemotherapeutic drugs and often represents a critical factor limiting an adequate dose-intensity of chemotherapy. Regarding the central nervous system (CNS), it is vulnerable to many forms of toxicity from chemotherapeutic agents, including encephalopathy syndromes and confusional states, seizures, headache, cerebrovascular complications, visual loss, cerebellar syndromes, and myelopathy. For a given drug, the occurrence of CNS toxicity depends on several factors, including the total dose, route of administration, presence of structural brain lesions, exposure to prior or concurrent irradiation, and interactions with other drugs. However, many of the neurotoxic reactions are rare and idiosyncratic, and remain unpredictable. Several forms of neuroprotection and rehabilitation are being investigated. Last, the so-called "chemobrain" is an emerging issue, as it is a model of a subtle of and long-lasting damage to neuronal structures from some antineoplastic agents.

A review of the use of biological agents for chronic inflammatory demyelinating polyradiculoneuropathy

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a group of idiopathic, acquired, immune-mediated inflammatory demyelinating diseases of the peripheral nervous system. A majority of patients with CIDP respond to "first-line" treatment with IVIG, plasmapheresis and/or corticosteroids. There exists insufficient evidence to ascertain the benefit of treatment with "conventional" immunosuppressive drugs. The inconsistent efficacy, long-term financial burden and health risks of non-specific immune altering therapy have drawn recurrent attention to the possible usefulness of a variety of biological agents that target key aspects in the CIDP immunopathogenic pathways. This review aims to give an updated account of the scientific rationale and potential use of biological therapeutics in patients with CIDP. No specific treatment recommendations are given. The discovery, development and application of biological markers by modern molecular diagnostic techniques may help identify drug-naïve or treatment-resistant CIDP patients most likely to respond to targeted immunotherapy.

[2011: What's new in dysimmune neuropathies]

There are strong research activities in the field of dysimmune neuropathies. In Guillain-Barré syndrome, new pathophysiological mechanisms have been demonstrated with the potential development of new therapies, a clinical prediction model is applicable early in the course of disease, and under investigation are new treatment strategies with adapted intravenous Ig dosages. In chronic inflammatory demyelinating polyneuropathies, current diagnostic tests are discussed but biomarkers are needed, such as histological changes or differential gene expression in nerve or skin biopsies. The exploration of novel therapeutic approaches including monoclonal antibodies and oral immunosuppressants, known from multiple sclerosis studies, suggests new approaches to treatment. Changes of the peripheral nerves on MR imaging are better known and the usefulness of serum antibodies is reviewed.