Circulating cytotoxic immune components in dominant Charcot-Marie-Tooth syndrome

Alpha-1 Antitrypsin Reduces Disease Progression in a Mouse Model of Charcot-Marie-Tooth Type 1A: A Role for Decreased Inflammation and ADAM-17 Inhibition

Charcot-Marie-Tooth disease type 1 (CMT1A) is a hereditary peripheral neuropathy for which there is no available therapy. Alpha-1 antitrypsin (AAT) is an abundant serine protease inhibitor with anti-inflammatory and immunomodulating properties. Here, we tested whether treatment with human AAT (hAAT) would have a therapeutic effect on CMT1A in a PMP22 transgenic mouse model. Our results show that hAAT significantly improved compound muscle action potential and histopathological features and decreased circulating IL-6 in CMT1A mice. We also investigated some of the possible underlying mechanisms in vitro. We confirmed that hAAT inhibits ADAM-17, a protease that has been implicated in blocking myelination. Furthermore, both hAAT and recombinant human AAT (rhAAT) were able to attenuate the activation of a macrophage/microglia cell line, markedly decreasing the activation of the MHC class II promoter and the expression of pro-inflammatory genes such as IL-1β and the endoplasmic reticulum (ER) stress marker ATF3. Taken together, our results demonstrate for the first time that hAAT is able to reduce the progression of CMT1A, possibly by dampening inflammation and by regulating ADAM-17. Given the already well-established safety profile of hAAT, specifically in AAT deficiency disease (AATD), we suggest that the findings of our study should be promptly investigated in CMT1A patients.

Restless legs syndrome--theoretical roles of inflammatory and immune mechanisms

Theories for restless legs syndrome (RLS) pathogenesis include iron deficiency, dopamine dysregulation and peripheral neuropathy. Increased prevalence of small intestinal bacterial overgrowth (SIBO) in controlled studies in RLS and case reports of post-infectious RLS suggest potential roles for inflammation and immunological alterations. A literature search for all conditions associated with RLS was performed. These included secondary RLS disorders and factors that may exacerbate RLS. All of these conditions were reviewed with respect to potential pathogenesis including reports of iron deficiency, neuropathy, SIBO, inflammation and immune changes. A condition was defined as highly-associated if there was a prevalence study that utilized an appropriate control group. Small case reports were recorded but not included as definite RLS-associated conditions. Fifty four diseases, syndromes and conditions have been reported to cause and/or exacerbate RLS. Of these, 38 have been reported to have a higher prevalence than age-matched controls, 9 have adequate sized reports and have general acceptance as RLS-associated conditions and 7 have been reported in case report form. Overall, 42 of the 47 RLS-associated conditions (89%) have also been associated with inflammatory and/or immune changes. In addition, 43% have been associated with peripheral iron deficiency, 40% with peripheral neuropathy and 32% with SIBO. Most of the remaining conditions have yet to be studied for these factors. The fact that 95% of the 38 highly-associated RLS conditions are also associated with inflammatory/immune changes suggests the possibility that RLS may be mediated or affected through these mechanisms. Inflammation can be responsible for iron deficiency and hypothetically could cause central nervous system iron deficiency-induced RLS. Alternatively, an immune reaction to gastrointestinal bacteria or other antigens may hypothetically cause RLS by a direct immunological attack on the central or peripheral nervous system.

Genetically determined neuropathy (CMT 1A) accompanied by immune dysfunction: a case report

Peripheral Myelin Protein 22 (PMP22) is mostly expressed in Schwann cells where it is essential in the compaction of myelin. The duplication of the PMP22 gene results in a hereditary demyelinating neuropathy of the Charcot-Marie-Tooth type 1A (CMT1A). So far there are only a few case reports suggesting that dysimmune mechanisms may take part in the pathophysiology of this disease. We describe three siblings carrying the duplication of the PMP22 gene, with a significant reduction of serum immunoglobulin G levels in all three cases and sural nerve vasculitis in the two women, which supports the proposition, that immune dysfunction may accompany this disease in some cases.

Study of antibodies to PMP22, IL-6 and TNF-alpha concentrations in serum in a CMTX1 family

To further understand X-linked dominant Charcot-Marie-Tooth disease (CMTX1), we followed a family of 22 members in China, including 8 patients, 2 asymptomatic carriers and 12 normal family members. Twenty-two family members as well as 60 normal controls unrelated to this family were screened for point mutation by denaturing high performance liquid chromatography (DHPLC). All patients and asymptomatic carriers from this family, but none of the normal population controls, showed a T-C transition at position 266 in codon 89 of exon 2 of connexin 32, resulting in a leucine to proline (L89P) exchange. To study whether the immune system is involved in the pathogenesis of CMTX1 patients and asymptomatic carriers, we measured serum concentrations of antibodies to peripheral nerve myelin protein 22 (PMP22), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) by ELISA. Serological results were also compared with those from GBS patients (n=11) and with normal subjects (n=20). Our analysis showed anti-PMP22 sera reactivity in 50.0% of CMTX1 patients, 63.6% of GBS patients and 10% of normal controls. Our results also indicated that anti-PMP22 antibodies in the CMTX1 family varied with sex. Anti-PMP22 antibodies were found in all male patients but not in all females, which may be one of the reasons that male patients usually have more severe clinical symptoms than that of female patients. There was no statistical difference in serum concentrations of IL-6 and TNF-alpha between CMTX1 patients and normal subjects. In conclusion, we identified a L89P mutation for the first time in a CMTX1 family in China and an associated response to PMP22 in males.

Immunological study of hereditary motor and sensory neuropathy type 1a (HMSN1a)

OBJECTIVES

Fifty three patients were studied to investigate whether autoimmune or inflammatory mechanisms could explain the phenotypic heterogeneity of patients with hereditary motor and sensory neuropathy type 1a (HMSN1a).

METHODS

Serum samples were examined for antibodies to peripheral nerve myelin protein 22 (PMP22), ganglioside GM1 and cauda equina homogenate, and interleukin-6 (IL-6) and soluble tumour necrosis factor receptor 1 (sTNF R1) concentrations. Serological results were compared with those from patients with other neuropathies (ONPs, n=30) and with normal subjects (n=51).

RESULTS

In the group as a whole, no relation emerged between clinical severity and any immune parameters. Immunohistochemical examination of four sural nerve biopsies did not show significant inflammatory infiltration. In a subset of 12 patients who experienced stepwise progression of disease, there was a trend towards a higher proportion having anti-PMP22 antibodies (33% v 15% of those with gradual disease progression, 3% ONPs, and no normal controls) and complement fixing antibodies to human cauda equina (25% v 5% with gradual progression, 8.6% ONPs, 3.9% normal controls, p=0.07).

CONCLUSIONS

Patients with HMSN1a and a stepwise disease progression may have an inflammatory, autoimmune component superimposed on the genetic condition.