Maria Ruiz-Soto

Giant cell arteritis and polymyalgia rheumatica: Role of cytokines in the pathogenesis and implications for treatment

OBJECTIVE To summarize the contribution of cytokines to pathogenesis, clinical manifestations and prognosis of polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). METHODS MEDLINE database search for studies published between 1980 and April 2008. RESULTS PMR and GCA are characterized by a hyperproduction of IL-6. The role of other circulating cytokines in their pathogenesis remains unclear. Cytokine mRNA in the arterial wall of GCA can distinguish different clinical subgroups of patients. The profile of T cell-derived cytokines in GCA suggests that it is a Th1-driven disease. The scarce number of studies makes difficult to evaluate the exact contribution of cytokine polymorphisms to their pathogenesis. Small studies have suggested the utility of TNF antagonists in patients with refractory PMR and GCA. However, these data have not been confirmed in controlled studies in patients with recent onset disease. CONCLUSION Further studies are needed to evaluate the role of circulating cytokines in PMR and GCA. The study of tissue cytokines has provided important insights into the mechanisms implicated in the local inflammatory response that occurs in GCA. The important advance in the knowledge of the role of cytokines in PMR and GCA will have clear implications for treatment.

Circulating cytokines in active polymyalgia rheumatica

Objective: To characterise the circulating cytokine profile and the cellular source of circulating cytokines in polymyalgia rheumatica (PMR). Methods: The study included 34 patients with active untreated PMR and 17 age-matched healthy controls (HC). Circulating cytokines were measured by cytometric bead array and ELISA. Intracellular cytokines were assessed in CD3+ and CD14+ cells by flow cytometry. Cytokines in cell culture supernatants were also determined after polyclonal stimulation of patients’ peripheral blood mononuclear cells. Results: Circulating levels of interleukin-6 (IL6) were significantly higher in subjects with active PMR than in HC. Corticosteroid (CS) treatment was followed by a decrease in the level of IL6. Intracellular cytokine staining showed that circulating monocytes did not produce higher amounts of proinflammatory cytokines in patients with PMR than in HC. There was a discordance between serum levels and cytokine-producing monocyte and T cells, and it was not possible to demonstrate a Th1 bias in the peripheral compartment. Conclusions: Active PMR is characterised by increased serum levels of IL6, but not of other proinflammatory cytokines, that are rapidly suppressed by CS treatment. As circulating monocytes do not show increased production of proinflammatory cytokines, IL6 may be mainly produced in the inflamed tissue. A study of the circulating cytokine profile and its cellular source may provide a clue to new therapeutic options.

Neuroprotective Effect of Bexarotene in the SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive weakness and muscle atrophy related to the loss of upper and lower motor neurons (MNs) without a curative treatment. There is experimental evidence suggesting that retinoids may be involved in ALS pathogenesis. Bexarotene (Bxt) is a retinoid-X receptor agonist used in the treatment of cutaneous lymphoma with a favorable safety profile whose effects have been recently investigated in other neurodegenerative diseases. In this study, we analyze the potential therapeutic effect of Bxt in the SOD1G93A mouse model of ALS. Mice were treated with Bxt or vehicle five times per week from day 60 onward. Survival, weight, and neuromuscular function studies together with histological and biochemical analyses were performed. Bxt significantly delayed motor function deterioration, ameliorated the loss of body weight, and extended mice survival up to 30% of the symptomatic period. Histological analyses of the lumbosacral spinal cord revealed that Bxt markedly delayed the early motor-neuron degeneration occurring at presymptomatic stages in ALS-transgenic mice. Bxt treatment contributed to preserve the MN homeostasis in the SOD1G93A mice. Particularly, it reduced the neuronal loss and the chromatolytic response, induced nucleolar hypertrophy, decreased the formation of ubiquitylated inclusions, and modulated the lysosomal response. As an agonist of the retinoic-X receptor (RXR) pathway, Bxt notably increased the nuclear expression of the RXRα throughout transcriptionally active euchromatin domains. Bxt also contributed to protect the MN environment by reducing reactive astrogliosis and preserving perisomatic synapsis. Overall, these neuroprotective effects suggest that treatment with Bxt could be useful in ALS, particularly in those cases related to SOD1 mutations.

Interleukin-1RN gene polymorphisms in elderly patients with rheumatic inflammatory chronic conditions: association of IL-1RN*2/2 genotype with polymyalgia rheumatica.

The objective of this study was to investigate whether there is an association between IL1RN polymorphism and disease susceptibility for three age-related inflammatory conditions: polymyalgia rheumatica (PMR), giant cell arteritis (GCA), and elderly-onset rheumatoid arthritis (EORA). A tandem-repeat polymorphism within IL1RN intron 2 was analyzed in 139 PMR, 69 GCA, and 156 RA patients (75 with EORA) as well as in 437 healthy subjects, together with the in vitro production of IL-1beta. Our results showed that the IL1RN*2/2 genotype was more frequent in PMR patients compared with controls (p = 0.032, odds ratio = 1.785, 95% confidence interval = 1.047-3.044) and GCA patients (p = 0.008, odds ratio = 4.661, 95% confidence interval = 1.352-16.065). We found no difference in the distribution of genotypes between PMR and EORA or between EORA and controls. However, the frequency of the IL-1RN*2/2 genotype had a tendency to be higher in patients with EORA compared with young onset RA. The presence of IL1RN*1 or IL1RN*2 allele was not associated with severity of the disease in PMR and GCA patients and did not influence the production of IL-1beta. In conclusion, the IL1RN*2 polymorphism in a homozygous state was associated with an increased susceptibility to PMR and may give some clues for a differential therapy with GCA.

Compensatory Motor Neuron Response to Chromatolysis in the Murine hSOD1(G93A) Model of Amyotrophic Lateral Sclerosis

We investigated neuronal self-defense mechanisms in a murine model of amyotrophic lateral sclerosis (ALS), the transgenic hSOD1G93A, during both the asymptomatic and symptomatic stages. This is an experimental model of endoplasmic reticulum (ER) stress with severe chromatolysis. As a compensatory response to translation inhibition, chromatolytic neurons tended to reorganize the protein synthesis machinery at the perinuclear region, preferentially at nuclear infolding domains enriched in nuclear pores. This organization could facilitate nucleo-cytoplasmic traffic of RNAs and proteins at translation sites. By electron microscopy analysis, we observed that the active euchromatin pattern and the reticulated nucleolar configuration of control motor neurons were preserved in ALS chromatolytic neurons. Moreover the 5′-fluorouridine (5′-FU) transcription assay, at the ultrastructural level, revealed high incorporation of the RNA precursor 5′-FU into nascent RNA. Immunogold particles of 5′-FU incorporation were distributed throughout the euchromatin and on the dense fibrillar component of the nucleolus in both control and ALS motor neurons. The high rate of rRNA transcription in ALS motor neurons could maintain ribosome biogenesis under conditions of severe dysfunction of proteostasis. Collectively, the perinuclear reorganization of protein synthesis machinery, the predominant euchromatin architecture, and the active nucleolar transcription could represent compensatory mechanisms in ALS motor neurons in response to the disturbance of ER proteostasis. In this scenario, epigenetic activation of chromatin and nucleolar transcription could have important therapeutic implications for neuroprotection in ALS and other neurodegenerative diseases. Although histone deacetylase inhibitors are currently used as therapeutic agents, we raise the untapped potential of the nucleolar transcription of ribosomal genes as an exciting new target for the therapy of some neurodegenerative diseases.

Retinoids and motor neuron disease: Potential role in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons (MN). This fatal disease is characterized by progressive muscular atrophy and unfortunately it does not have an effective treatment. Although a small proportion of ALS cases have a familiar origin, the vast majority of them are thought to have a sporadic origin. Although the pathogenesis of ALS has not been fully elucidated, various disorders in different cellular functions such as gene expression, protein metabolism, axonal transport and glial cell disorders have been linked to MN degeneration. Among them, proteostasis is one of the best studied. Retinoids are vitamin A-derived substances that play a crucial role in embryogenesis, development, programmed cell death and other cellular functions. Retinoid agonists behave as transcription factors throughout the activation of the nuclear retinoid receptors. Several reports in the literature suggest that retinoids are involved in proteostasis regulation, by modulating its two major pathways, the ubiquitin-proteasome system and the autophagy-lysosome response. Additionally, there are some evidences for a role of retinoids themselves, in ALS pathogenesis. In this review, we discuss the importance of proteostasis disruption as a trigger for MN degeneration and the capability of retinoids to modulate it, as well as the potential therapeutic role of retinoids as a new therapy in ALS.

Why do motor neurons degenerate? Actualization in the pathogenesis of amyotrophic lateral sclerosis.

Abstract Introduction Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons. Although a small proportion of ALS cases are familial in origin and linked to mutations in specific genes, most cases are sporadic and have a multifactorial aetiology. Some recent studies have increased our knowledge of ALS pathogenesis and raised the question of whether this disorder is a proteinopathy, a ribonucleopathy, an axonopathy, or a disease related to the neuronal microenvironment. Development This article presents a review of ALS pathogenesis. To this end, we have reviewed published articles describing either ALS patients or ALS animal models and we discuss how the main cellular pathways (gene processing, protein metabolism, oxidative stress, axonal transport, relationship with neuronal microenvironment) may be involved in motor neurons degeneration. Conclusions ALS pathogenesis has not been fully elucidated. Recent studies suggest that although initial triggers may differ among patients, the final motor neurons degeneration mechanisms are similar in most patients once the disease is fully established.

¿Por qué degeneran las motoneuronas? Actualización en la patogenia de la esclerosis lateral amiotrófica

INTRODUCTION Amyotrophic lateral sclerosis (ALS) is the most common neurodegenerative disease affecting motor neurons. Although a small proportion of ALS cases are familial in origin and linked to mutations in specific genes, most cases are sporadic and have a multifactorial aetiology. Some recent studies have increased our knowledge of ALS pathogenesis and raised the question of whether this disorder is a proteinopathy, a ribonucleopathy, an axonopathy, or a disease related to the neuronal microenvironment. DEVELOPMENT This article presents a review of ALS pathogenesis. To this end, we have reviewed published articles describing either ALS patients or ALS animal models and we discuss how the main cellular pathways (gene processing, protein metabolism, oxidative stress, axonal transport, relationship with neuronal microenvironment) may be involved in motor neurons degeneration. CONCLUSIONS ALS pathogenesis has not been fully elucidated. Recent studies suggest that although initial triggers may differ among patients, the final motor neurons degeneration mechanisms are similar in most patients once the disease is fully established.

Nerve ultrasonography in early Guillain-Barré syndrome: a need for large prospective studies

Dear Editor, We read with interest the article by Grimm et al. (2014) describing the role of nerve ultrasonography in the acute phase of Guillain-Barré syndrome (GBS). We wish to call attention to the paper by Gallardo et al. (2014), published online on August 21, 2014, describing clinico-electrophysiological, ultrasonographic, and pathological studies in six consecutive early GBS patients. As in the Grimm et al. (2014) report, our study revealed ultrasonographic changes in cervical nerves (fifth to seventh) in four patients, which included significant increase of cross-sectional area, blurred boundaries of the corresponding ventral rami, or both. Autopsy study in one case showed widespread endoneurial inflammatory changes in cervical and lumbar nerves extending to epi-perineurium, this feature accounting for the observed loss of physiologic hyper-echoic epineurial rim. Such spinal nerve features corroborate the description by Haymaker and Kernohan (1949): “As a whole, the observed pathological changes were usually more prominent in the region where the motor and sensory roots join to form the spinal nerve. They occurred to a diminishing degree in the adjacent parts of the spinal roots, especially the anterior roots, and seldom reached the most proximal portion of the root.” Grimm et al. (2014) found that on ultrasonography there was significant increase of cross-sectional area in all scanned nerves excepting for ulnar nerve in upper limbs and sural nerve in lower limbs. Contrariwise, in our series upperand lower-limb nerve ultrasonography showed abnormal cross-sectional area (over mean+ 2SD) in just 8.8% of scanned nerves (Gallardo et al., 2014). Clearly, we need large and prospective ultrasonographic studies in GBS so that we can understand this better. Such studies should be done on a multinational, multicenter basis.