Variation in experimental autoimmune encephalomyelitis scores in a mouse model of multiple sclerosis

Neuropathic Pain in Multiple Sclerosis and Its Animal Models: Focus on Mechanisms, Knowledge Gaps and Future Directions

Multiple sclerosis (MS) is a multifaceted, complex and chronic neurological disease that leads to motor, sensory and cognitive deficits. MS symptoms are unpredictable and exceedingly variable. Pain is a frequent symptom of MS and manifests as nociceptive or neuropathic pain, even at early disease stages. Neuropathic pain is one of the most debilitating symptoms that reduces quality of life and interferes with daily activities, particularly because conventional pharmacotherapies do not adequately alleviate neuropathic pain. Despite advances, the mechanisms underlying neuropathic pain in MS remain elusive. The majority of the studies investigating the pathophysiology of MS-associated neuropathic pain have been performed in animal models that replicate some of the clinical and neuropathological features of MS. Experimental autoimmune encephalomyelitis (EAE) is one of the best-characterized and most commonly used animal models of MS. As in the case of individuals with MS, rodents affected by EAE manifest increased sensitivity to pain which can be assessed by well-established assays. Investigations on EAE provided valuable insights into the pathophysiology of neuropathic pain. Nevertheless, additional investigations are warranted to better understand the events that lead to the onset and maintenance of neuropathic pain in order to identify targets that can facilitate the development of more effective therapeutic interventions. The goal of the present review is to provide an overview of several mechanisms implicated in neuropathic pain in EAE by summarizing published reports. We discuss current knowledge gaps and future research directions, especially based on information obtained by use of other animal models of neuropathic pain such as nerve injury.

Human placental extract attenuates neurological symptoms in the experimental autoimmune encephalomyelitis model of multiple sclerosis-a putative approach in MS disease?

BACKGROUND

Different studies have demonstrated the anti-inflammatory effects of human placental extract both in vivo and in vitro. Considering the chronic inflammatory nature of multiple sclerosis (MS) disease, we examined whether or not the administration of human placental extract is able to attenuate the neurological symptoms detected in experimental autoimmune encephalomyelitis (EAE) model of MS.

METHODS

The injected myelin oligodendrocyte glycoprotein (MOG) induced EAE in mice, and treatment began from day 4 post-injection by intraperitoneal administration of 0.2 mg/kg human placental extract, repeated every other day up to day 31 post-injection. At the end of the treatment, luxol fast blue (LBS) staining and hematoxylin and eosin (H&E) staining were performed to evaluate the demyelination of neurons and inflammatory responses, respectively. Further assessed were the serum concentrations of IL-23 and IL-27.

RESULTS

The administration of human placental extract was able to significantly reduce the mean clinical score in EAE mice, decrease the pro-inflammatory process and attenuate neural demyelination. Moreover, while the serum concentration of IL-23 was significantly diminished in the EAE mice receiving human placental extract compared to the non-treated EAE group, IL-27 concentration was significantly increased.

CONCLUSIONS

Our findings demonstrated the administration of human placental extract could significantly attenuate the neurological symptoms in the EAE model of MS in part through modulating the serum levels of IL-23 and IL-27 and enhancing neuroprotection and myelin repair.

Protective effects of pharmacological therapies in animal models of multiple sclerosis: a review of studies 2014-2019

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. The disability caused by inflammatory demyelination clinically dominates the early stages of relapsing-remitting MS and is reversible. Once there is considerable loss of axons, MS patients enter a secondary progressive stage. Disease-modifying drugs currently in use for MS suppress the immune system and reduce relapse rates but are not effective in the progressive stage. Various animal models of MS (mostly mouse and rat) have been established and proved useful in studying the disease process and response to therapy. The experimental autoimmune encephalomyelitis animal studies reviewed here showed that a chronic progressive disease can be induced by immunization with appropriate amounts of myelin oligodendrocyte glycoprotein together with mycobacterium tuberculosis and pertussis toxin in Freund's adjuvant. The clinical manifestations of autoimmune encephalomyelitis disease were prevented or reduced by treatment with certain pharmacological agents given prior to, at, or after peak disease, and the agents had protective effects as shown by inhibiting demyelination and damage to neurons, axons and oligodendrocytes. In the cuprizone-induced toxicity animal studies, the pharmacological agents tested were able to promote remyelination and increase the number of oligodendrocytes when administered therapeutically or prophylactically. A monoclonal IgM antibody protected axons in the spinal cord and preserved motor function in animals inoculated with Theiler's murine encephalomyelitis virus. In all these studies the pharmacological agents were administered singly. A combination therapy may be more effective, especially using agents that target neuroinflammation and neurodegeneration, as they may exert synergistic actions.

Role of orexin-A in experimental autoimmune encephalomyelitis

The aim of this study was to evaluate the effects of orexin-A (OX-A) on behavioral and pathological parameters and on gene expression of some multiple sclerosis-related peptides in a model of experimental autoimmune encephalomyelitis (EAE). EAE was induced by subcutaneous administration of MOG 35-55. Following immunization, the treatment was initiated by using SB.334867 (orexin-1 receptor antagonist) and/or OX-A. Locomotor activity and exploratory behaviors were monitored using open field and T-maze continuous alternation task (T-CAT) respectively. Pain sensitivity was assessed by hot-plate test. Histopathological assessments were performed by H&E staining. The expression of TGF-β, MBP, MMP-9, IL-12, iNOS and MCP-1 were measured using real-time PCR method in lumbar spinal cord. OX-A administration in EAE mice remarkably attenuated the clinical symptoms, increased latency response in hot plate test, inhibited infiltration of inflammatory cells, up-regulated mRNA expression of TGF-β as well as MBP and down-regulated mRNA expression of iNOS, MMP-9 and IL-12. In contrast SB.334867 administration in EAE mice deteriorated the clinical symptoms, decreased the alternation in T-CAT, increased infiltration of inflammatory cells, down-regulated mRNA expression of TGF-β and MBP and up-regulated mRNA expression of iNOS. Results of this study suggest that the orexinergic system might be involved in pathological development of EAE. These findings suggest orexinergic system as a potential target for treatment of multiple sclerosis.

Ginger extracts influence the expression of IL-27 and IL-33 in the central nervous system in experimental autoimmune encephalomyelitis and ameliorates the clinical symptoms of disease

The immunomodulatory effects of the IL-27 and IL-33 and the anti-inflammatory effects of ginger have been reported in some studies. The aim was to evaluate the effects of the ginger extract on the expression of IL-27 and IL-33 in a model of experimental autoimmune encephalomyelitis (EAE). In PBS-treated EAE mice the expression of IL-27 P28 was significantly lower whereas the expression of IL-33 was significantly higher than unimmunized control mice. In 200 and 300 mg/kg ginger-treated EAE groups the expression of IL-27 P28 and IL-27 EBI3 was significantly higher whereas the expression of IL-33 was significantly lower than PBS-treated EAE mice. The EAE clinical symptoms and the pathological scores were significantly lower in ginger-treated EAE groups. These results showed that the ginger extract modulates the expression of the IL-27 and IL-33 in the spinal cord of EAE mice and ameliorates the clinical symptoms of disease.

Targeting S1P receptors in experimental autoimmune encephalomyelitis in mice improves early deficits in locomotor activity and increases ultrasonic vocalisations

Fingolimod (FTY720) is an oral therapy for relapsing remitting multiple sclerosis (MS) and targets sphingosine 1-phosphate receptors (S1PRs). FTY720 also rescues animals from experimental autoimmune encephalomyelitis (EAE), an animal model of MS. The protective effects of FTY720 in EAE are primarily scored manually by examining weight loss and limb paralysis that begins around 10-12 days after immunisation. To our knowledge, pre-clinical effects of FTY720 on animal behaviour early in EAE have not been explored. Here, we developed an automated behaviour monitoring system to examine the early effects of FTY720 on subtle pre-symptomatic behaviour of mice induced with EAE. Our automated home-cage monitoring system (AHC-MS) enabled non-contact detection of movement and ultrasonic vocalisations (USVs) of mice induced with EAE, thus allowing detection of subtle changes in mouse behaviour before paralysis occurs. Mice receiving FTY720 emit longer USVs and display higher levels of motor activity than vehicle-treated EAE mice before clinical symptoms become apparent. Importantly, this study promotes the 3Rs ethics (replacement, reduction and refinement) in the EAE animal model and may also improve pre-screening of potentially novel MS therapies. In addition, this is the first report showing the early effects of FTY720 in EAE which underscores its protective effects.