Anti-inflammatory strategies to prevent axonal injury in multiple sclerosis

Differential expression of STAT3 gene and its regulatory long non-coding RNAs, namely lnc-DC and THRIL, in two eastern Iranian ethnicities with multiple sclerosis

OBJECTIVE

Genome-wide association studies (GWASs) revealed that variants of STAT3 are associated with multiple sclerosis (MS) risk. There are several studies showing the effect of ethnicity and genetic background on the characteristics of MS. Here, we aimed to investigate STAT3 gene expression status along with its two regulatory long non-coding RNAs, lnc-DC and THRIL, in order to compare the expression of these target genes among two different ethnicities in the east of Iran.

METHODS

A case-control study was performed between two groups of MS populations in east of Iran. We recruited individuals with Kurdish ethnicity from North Khorasan and Sistani ethnicity from southeast of Iran. The peripheral blood mononuclear cells were obtained from all participants, and total RNA was extracted. The gene expression of the selected genes was evaluated by qPCR.

RESULTS

The expression of THRIL in North Khorasan MS patients was significantly higher than controls (P = 0.03). The results of simultaneous analysis of expression of the target genes (STAT3, THRIL, and lnc-DC) in both ethnic groups failed to show any significant difference between the MS patients and controls (P > 0.05). In addition, the expression of STAT3 and THRIL genes in Sistani MS patients was statistically meaningful lower than healthy controls (P < 0.05).

CONCLUSION

To our knowledge, this is the first study that compared the expression of the STAT3 gene and its regulatory molecules between two ethnic groups of Iranian MS patients. We suggested that STAT3 and its associated molecules might be differentially expressed and regulated in MS patients with different genetic background.

Inhibition of Drp1 hyper-activation is protective in animal models of experimental multiple sclerosis

Multiple Sclerosis (MS), a leading neurological disorder of young adults, is characterized by the loss of oligodendrocytes (OLs), demyelination, inflammation and neuronal degeneration. Here we show that dynamin-related protein 1 (Drp1), a mitochondrial fission protein, is activated in primary OL cells exposed to TNF-α induced inflammation or oxidative stress, as well as in EAE-immunized and cuprizone toxicity-induced demyelinating mouse models. Inhibition of Drp1 hyper-activation by the selective inhibitor P110 abolishes Drp1 translocation to the mitochondria, reduces mitochondrial fragmentation and stems necrosis in primary OLs exposed to TNF-α and H₂O₂. Notably, in both types of mouse models, treatment with P110 significantly reduces the loss of mature OLs and demyelination, attenuates the number of active microglial cells and astrocytes, yet has no effect on the differentiation of oligodendrocyte precursor cells. Drp1 activation appears to be mediated through the RIPK1/RIPK3/MLKL/PGAM5 pathway during TNF-α-induced oligodendroglia necroptosis. Our results demonstrate a critical role of Drp1 hyper-activation in OL cell death and suggest that an inhibitor of Drp1 hyper-activation such as P110 is worth exploring for its ability to halt or slow the progression of MS.

Neurodegeneration in multiple sclerosis involves multiple pathogenic mechanisms

Multiple sclerosis (MS) is a complex autoimmune disease that impairs the central nervous system (CNS). The neurological disability and clinical course of the disease is highly variable and unpredictable from one patient to another. The cause of MS is still unknown, but it is thought to occur in genetically susceptible individuals who develop disease due to a nongenetic trigger, such as altered metabolism, a virus, or other environmental factors. MS patients develop progressive, irreversible, neurological disability associated with neuronal and axonal damage, collectively known as neurodegeneration. Neurodegeneration was traditionally considered as a secondary phenomenon to inflammation and demyelination. However, recent data indicate that neurodegeneration develops along with inflammation and demyelination. Thus, MS is increasingly recognized as a neurodegenerative disease triggered by an inflammatory attack of the CNS. While both inflammation and demyelination are well described and understood cellular processes, neurodegeneration might be defined by a diverse pool of any of the following: neuronal cell death, apoptosis, necrosis, and virtual hypoxia. In this review, we present multiple theories and supporting evidence that identify common biological processes that contribute to neurodegeneration in MS.

Mechanisms of neuronal dysfunction and degeneration in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system. Due to its high prevalence, MS is the leading cause of non-traumatic neurological disability in young adults in the United States and Europe. The clinical disease course is variable and starts with reversible episodes of neurological disability in the third or fourth decade of life. This transforms into a disease of continuous and irreversible neurological decline by the sixth or seventh decade. Available therapies for MS patients have little benefit for patients who enter this irreversible phase of the disease. It is well established that irreversible loss of axons and neurons are the major cause of the irreversible and progressive neurological decline that most MS patients endure. This review discusses the etiology, mechanisms and progress made in determining the cause of axonal and neuronal loss in MS.

Prospects of repair in multiple sclerosis

In multiple sclerosis, physiological repair mechanisms can help the nervous system to recover from tissue injury. Enhancing such repair mechanisms is an important, and increasingly realistic, therapeutic goal in multiple sclerosis. With respect to remyelination, several promising therapeutic avenues are currently being explored, including stem cell transplantation, LINGO-1, prolactin and glatiramer acetate. Glatiramer acetate is believed to act by the induction of specific populations of anti-inflammatory Th2 cells or Type 2 monocytes which infiltrate sites of injury in the nervous system where they release anti-inflammatory cytokines leading to bystander suppression of inflammation. In addition, these cells can release neurotrophic factors such as BDNF and IGF-1 which have been shown to stimulate the differentiation of oligodendrocyte precursor cells and thus enhance remyelination. In addition, neurotrophic factors released in response to glatiramer acetate may stimulate the differentiation of neuronal progenitor cells into mature neurones that can replace neurones lost through the disease process. This repair capacity of glatiramer acetate may contribute to the long-term well-being of patients with multiple sclerosis treated with glatiramer acetate.

Immunological aspects of axon injury in multiple sclerosis

The role of immune-mediated axonal injury in the induction of nonremitting functional deficits associated with multiple sclerosis is an area of active research that promises to substantially alter our understanding of the pathogenesis of this disease and modify or change our therapeutic focus. This review summarizes the current state of research regarding changes in axonal function during demyelination, provides evidence of axonal dysmorphia and degeneration associated with demyelination, and identifies the cellular and molecular effectors of immune-mediated axonal injury. Finally, a unifying hypothesis that links neuronal stress associated with demyelination-induced axonal dysfunction to immune recognition and immunopathology is provided in an effort to shape future experimentation.

Fortschritte im Verständnis von Pathogenese und Immuntherapie der Multiplen Sklerose

In this article recent advances in research on the pathogenesis of multiple sclerosis (MS) are summarized. New evidence from molecular histopathology is discussed focussing on neurodegenerative aspects. In addition findings with a direct effect on therapeutic decisions are presented which have contributed to improved immunotherapy. During the last decade important advances in immunotherapy have proven especially useful for patients with relapsing-remitting MS. Escalating algorithms are available for both relapses and long-term immunotherapy. Novel therapeutic approaches with monoclonal antibodies have increasing importance, yet side effects are not completely understood. The pathogenetic insights presented here may open new avenues for novel immunotherapies and lead to individualized MS therapy in the future. Limitations are given for primary progressive MS due to the lack of suitable tissue specimens and experimental models. Neuroprotective treatment strategies aiming at the protection of glial and neuronal cells are still in early stages of development.

Poly(ADP-ribose) polymerase-1 activation in a primate model of multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated disabling neurological disorder involving inflammation, demyelination, axonal damage, and neurodegeneration. Poly(ADP-ribose)polymerase-1 (PARP-1), a nuclear enzyme linked to DNA repair, has been shown to regulate the cellular inflammatory response through interactions with nuclear factor-kappaB. Extensive PARP-1 activation can, by separate mechanisms, also cause cell death. PARP-1 activation in brain occurs in several settings associated with oxidative stress and DNA damage, and PARP-1 inhibition has been shown to attenuate inflammation and improve neuronal survival in these settings. Here we studied the pattern of PARP-1 activation in a nonhuman primate model of MS, marmoset (Callithrix jacchus) experimental allergic encephalomyelitis (EAE). Characteristic of this model is relapsing and remitting focal demyelination typical of human MS. Immunostaining for poly(ADP-ribose), the enzymatic product of PARP-1, showed PARP-1 activation specifically in plaque areas of EAE brains. Robust immunostaining was found in astrocytes surrounding demyelinated EAE plaques and in scattered nearby microglia, oligodendrocytes, and neurons. The immunostaining also suggested PARP-1 activation in occasional endothelial cells surrounded by microglia or infiltrating peripheral blood cells. Given the importance of PARP-1 in both inflammation and cell death processes, these findings suggest that PARP-1 activation may be a significant factor in the pathogenesis of MS.

Psychiatric manifestations of autoimmune disorders

Psychiatric symptoms are common to many autoimmune disorders. Patients often will have mood disorders, anxiety, cognitive deficits, delirium, and psychosis. These symptoms may reflect the direct or indirect effect of the autoimmune disorder on the central nervous system, may be related to medications used to treat the disorder, or may be a direct psychologic impact from suffering with the autoimmune disorder. Accurately recognizing the psychiatric component and generating a differential diagnosis is a complex task for the treating physician. Treatment of the psychiatric component to the disorder often will include addressing steroid induced side effects, psychotropic medications, psychotherapy, patient and family education, and a strong physician-patient relationship.

Beneficial effect of erythropoietin on experimental allergic encephalomyelitis

We have known for a long time that erythropoietin signaling plays a key role in bone marrow erythrocyte proliferation. However, recent studies have indicated that erythropoietin also may have protective effects on the nervous system. This unexpected role remains incompletely characterized. To investigate the potential neuroprotective role of erythropoietin in the central nervous system, we assessed its effects on a well-characterized autoimmune demyelinating model of multiple sclerosis-myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) in the mouse. We found that erythropoietin administered intravenously for 14 days after the onset of symptoms reduced both disease severity and duration of maximum impairment at dose levels as low as 50U/kg (p < 0.001). We assessed the neuropathology of diseased spinal cords and found that erythropoietin-treated EAE animals had reduced axonal damage, inflammatory cell infiltration and demyelination, and diminished blood-brain barrier leakage when compared with saline-treated EAE controls. Moreover, the pronounced upregulation of spinal cord major histocompatibility complex (MHC) class II expression found in saline-treated EAE was significantly reduced in erythropoietin-treated animals, a finding we replicated in vitro, using microglial cultures. The notion that short-term erythropoietin therapy might be of clinical benefit in human autoimmune demyelinating diseases needs investigation.

Axonal damage in multiple sclerosis: a complex issue in a complex disease

Multiple sclerosis is no longer considered to simply be an autoimmune demyelinating disease. Axonal destruction is another central pathological feature and a contributor to the accumulating disability of disease progression. The mechanism underlying axonal pathology has not been fully clarified but does not appear to be a simple one. The relationship between axonal damage and other components of the pathological features such as demyelination, inflammation and remyelination are under intense investigation. Experimental data suggest that therapeutic interventions such as the induction of rapid remyelination may lead to the protection of axons. In addition to immunomodulation, future strategies for neuroprotection may be of great importance.

Axonal damage is reduced following glatiramer acetate treatment in C57/bl mice with chronic-induced experimental autoimmune encephalomyelitis

Glatiramer acetate (GA) is efficacious in reducing demyelinating-associated exacerbations in patients with relapsing-remitting multiple sclerosis (RRMS) and in several experimental autoimmune encephalomyelitis (EAE) models. Here we report that GA reduced the clinical and pathological signs of mice in chronic EAE induced by myelin oligodendrocyte glycoprotein (MOG). GA-treated mice demonstrated only mild focal inflammation, and less demyelination, compared with controls. Moreover, we also found minimal axonal disruption, as assessed by silver staining, antibodies against amyloid precursor protein (APP) and non-phosphorylated neurofilaments (SMI-32), in the GA-treated group. In conclusion, our study demonstrated for the first time that axonal damage is reduced following GA treatment in C57/bl mice with chronic MOG-induced EAE.