Jacopo C. DiFrancesco

Anti–amyloid β autoantibodies in cerebral amyloid angiopathy–related inflammation: Implications for amyloid-modifying therapies

Cerebral amyloid angiopathy–related inflammation (CAA‐ri) is characterized by vasogenic edema and multiple cortical/subcortical microbleeds, sharing several aspects with the recently defined amyloid‐related imaging abnormalities (ARIA) reported in Alzheimers disease (AD) passive immunization therapies. Herein, we investigated the role of anti–amyloid β (Aβ) autoantibodies in the acute and remission phases of CAA‐ri.

Recessive Loss-of-Function Mutation in the Pacemaker HCN2 Channel Causing Increased Neuronal Excitability in a Patient with Idiopathic Generalized Epilepsy

The hyperpolarization-activated Ih current, coded for by hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, controls synaptic integration and intrinsic excitability in many brain areas. Because of their role in pacemaker function, defective HCN channels are natural candidates for contributing to epileptogenesis. Indeed, Ih is pathologically altered after experimentally induced seizures, and several independent data indicate a link between dysfunctional HCN channels and different forms of epilepsy. However, direct evidence for functional changes of defective HCN channels correlating with the disease in human patients is still elusive. By screening families with epilepsy for mutations in Hcn1 and Hcn2 genes, we found a recessive loss-of-function point mutation in the gene coding for the HCN2 channel in a patient with sporadic idiopathic generalized epilepsy. Of 17 screened members of the same family, the proband was the only one affected and homozygous for the mutation. The mutation (E515K) is located in the C-linker, a region known to affect channel gating. Functional analysis revealed that homomeric mutant, but not heteromeric wild-type/mutant channels, have a strongly inhibited function caused by a large negative shift of activation range and slowed activation kinetics, effectively abolishing the HCN2 contribution to activity. After transfection into acutely isolated newborn rat cortical neurons, homomeric mutant, but not heteromeric wild type/mutant channels, lowered the threshold of action potential firing and strongly increased cell excitability and firing frequency when compared with wild-type channels. This is the first evidence in humans for a single-point, homozygous loss-of-function mutation in HCN2 potentially associated with generalized epilepsy with recessive inheritance.

Validation of Clinicoradiological Criteria for the Diagnosis of Cerebral Amyloid Angiopathy-Related Inflammation.

IMPORTANCE Cerebral amyloid angiopathy-related inflammation (CAA-ri) is an important diagnosis to reach in clinical practice because many patients with the disease respond to immunosuppressive therapy. Reliable noninvasive diagnostic criteria for CAA-ri would allow some patients to avoid the risk of brain biopsy. OBJECTIVE To test the sensitivity and specificity of clinical and neuroimaging-based criteria for CAA-ri. DESIGN, SETTING, AND PARTICIPANTS We modified the previously proposed clinicoradiological criteria and retrospectively analyzed clinical medical records and magnetic resonance imaging fluid-attenuated inversion recovery and gradient-echo scans obtained from individuals with CAA-ri and noninflammatory CAA. At 2 referral centers between October 1, 1995, and May 31, 2013, and between January 1, 2009, and December 31, 2011, participants included 17 individuals with pathologically confirmed CAA-ri and 37 control group members with pathologically confirmed noninflammatory CAA. The control group was further divided into those with past lobar intracerebral hemorrhage (ICH) (n = 21) and those with cerebral microbleeds only and no history of ICH (n = 16). The dates of our analysis were September 1, 2012, to August 31, 2015. MAIN OUTCOMES AND MEASURES The sensitivity and specificity of prespecified criteria for probable CAA-ri (requiring asymmetric white matter hyperintensities extending to the subcortical white matter) and possible CAA-ri (not requiring the white matter hyperintensities to be asymmetric). RESULTS The 17 patients in the CAA-ri group were a mean (SD) of 68 (8) years and 8 (47%) were women. In the CAA-ri group, 14 of 17 (82%) met the criteria for both probable and possible CAA-ri. In the control group having noninflammatory CAA with lobar ICH, 1 of 21 (5%) met the criteria for possible CAA-ri, and none met the criteria for probable CAA-ri. In the control group having noninflammatory CAA with no ICH, 11 of 16 (69%) met the criteria for possible CAA-ri, and 1 of 16 (6%) met the criteria for probable CAA-ri. These findings yielded a sensitivity and specificity of 82% and 97%, respectively, for the probable criteria and a sensitivity and specificity of 82% and 68%, respectively, for the possible criteria. CONCLUSIONS AND RELEVANCE Our data suggest that a reliable diagnosis of CAA-ri can be reached from basic clinical and magnetic resonance imaging information alone, with good sensitivity and excellent specificity.

Dysfunctional HCN ion channels in neurological diseases

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed as four different isoforms (HCN1-4) in the heart and in the central and peripheral nervous systems. HCN channels are activated by membrane hyperpolarization at voltages close to resting membrane potentials and carry the hyperpolarization-activated current, dubbed If (funny current) in heart and Ih in neurons. HCN channels contribute in several ways to neuronal activity and are responsible for many important cellular functions, including cellular excitability, generation, and modulation of rhythmic activity, dendritic integration, transmission of synaptic potentials, and plasticity phenomena. Because of their role, defective HCN channels are natural candidates in the search for potential causes of neurological disorders in humans. Several data, including growing evidence that some forms of epilepsy are associated with HCN mutations, support the notion of an involvement of dysfunctional HCN channels in different experimental models of the disease. Additionally, some anti-epileptic drugs are known to modify the activity of the Ih current. HCN channels are widely expressed in the peripheral nervous system and recent evidence has highlighted the importance of the HCN2 isoform in the transmission of pain. HCN channels are also present in the midbrain system, where they finely regulate the activity of dopaminergic neurons, and a potential role of these channels in the pathogenesis of Parkinson’s disease has recently emerged. The function of HCN channels is regulated by specific accessory proteins, which control the correct expression and modulation of the neuronal Ih current. Alteration of these proteins can severely interfere with the physiological channel function, potentially predisposing to pathological conditions. In this review we address the present knowledge of the association between HCN dysfunctions and neurological diseases, including clinical, genetic, and physiopathological aspects.

Prodromal Alzheimer's disease presenting as cerebral amyloid angiopathy-related inflammation with spontaneous amyloid-related imaging abnormalities and high cerebrospinal fluid anti-Aβ autoantibodies.

Cerebral amyloid angiopathy-related inflammation (CAA-ri), a rare form of vasculitis associated with amyloid-β (Aβ) deposition in vessel walls, has been proposed as a spontaneous human model of the amyloid-related imaging abnormalities (ARIA) occurring after anti-Aβ immunotherapy for the treatment of Alzheimers disease (AD). We describe a case of a patient with biopsy-proven CAA-ri and prodromal AD, confirmed by means of neuropsychological examination after 20 months follow-up, presenting with ARIA and high levels of cerebrospinal fluid anti-Aβ autoantibodies. This case further supports the analogies between the inflammatory response driven by anti-Aβ immunotherapy and that spontaneously occurring in CAA-ri.

Anti-Aβ Autoantibodies in Amyloid Related Imaging Abnormalities (ARIA): Candidate Biomarker for Immunotherapy in Alzheimer's Disease and Cerebral Amyloid Angiopathy.

Amyloid-related imaging abnormalities (ARIA) represent the major severe side effect of amyloid-beta (Aβ) immunotherapy for Alzheimer’s disease (AD). Early biomarkers of ARIA represent an important challenge to ensure safe and beneficial effects of immunotherapies, given that different promising clinical trials in prodromal and subjects at risk for AD are underway. The recent demonstration that cerebrospinal fluid (CSF) anti-Aβ autoantibodies play a key role in the development of the ARIA-like events characterizing cerebral amyloid angiopathy-related inflammation generated great interest in the field of immunotherapy. Herein, we critically review the growing body of evidence supporting the monitoring of CSF anti-Aβ autoantibody as a promising candidate biomarker for ARIA in clinical trials.

TREX1 C-terminal frameshift mutations in the systemic variant of retinal vasculopathy with cerebral leukodystrophy

AbstractRetinal vasculopathy with cerebral leukodystrophy (RVCL) is an adult-onset disorder caused by C-terminal heterozygous frameshift (fs) mutations in the human 3′–5′ DNA exonuclease TREX1. Hereditary systemic angiopathy (HSA) is considered a variant of RVCL with systemic involvement of unknown genetic cause, described in a unique family so far. Here we describe the second case of RVCL with systemic involvement, characterized by cerebral calcifications and pseudotumoral lesions, retinopathy, osteonecrosis, renal and hepatic failure. The genetic screening of TREX1 in this patient revealed the novel heterozygous T270fs mutation on the C-terminal region. On the same gene, we found the V235fs mutation, formerly shown in RVCL, in one patient previously reported with HSA. These mutations lead to important alterations of the C-terminal of the protein, with the loss of the transmembrane helix (T270fs) and the insertion of a premature stop codon, resulting in a truncated protein (V235fs). Functional analysis of T270fs-mutated fibroblasts showed a prevalent localization of the protein in the cytosol, rather than in the perinuclear region. RVCL with systemic involvement is an extremely rare condition, whose diagnosis is complex due to multiorgan manifestations, unusual radiological and histopathological findings, not easily attributable to a single disease. It should be suspected in young adults with systemic microangiopathy involving retina, liver, kidney, bones and brain. Here we confirm the causative role played by TREX1 autosomal dominant fs mutations disrupting the C-terminal of the protein, providing a model for the study of stroke in young adults.

Cerebrospinal fluid levels of BAFF and APRIL in untreated multiple sclerosis

OBJECTIVE AND SUBJECTS To examine in vivo levels of BAFF (B-cell activating factor of the tumor necrosis factor family) and APRIL (a proliferation-inducing ligand) in both the cerebrospinal fluid (CSF) and serum of 30 naïve MS patients and 79 subjects affected by acute or chronic inflammatory or non-inflammatory neurological diseases. DESIGN Case-control study. RESULTS No difference among groups was evidenced in serum BAFF or APRIL levels. By contrast, CSF levels of BAFF in MS (mean 144.3 pg/ml+/-141.2), although not significantly different from those observed in NIND (164.2 pg/ml+/-92.0), acute peripheral OIND (243.1 pg/ml+/-139.0) or chronic OIND (240.2 pg/ml+/-122.5), were significantly higher in acute central OIND patients (1274.0 pg/ml+/-803.8; p<0.001 vs. all groups). Similarly, CSF APRIL levels in MS (1541.0 pg/ml+/-1071.0), NIND (2629.0 pg/ml+/-1669.0), acute peripheral OIND (2834.0 pg/ml+/-1118.) or chronic OIND (2764.0 pg/ml+/-659.7) were not significantly different, while they were significantly higher in acute central OIND (6218.0 pg/ml+/-3790.0; p<0.001 vs. MS and NIND; and p<0.05 vs. acute peripheral OIND). CONCLUSIONS Our results strongly suggest that further investigation is warranted to elucidate the role of BAFF and APRIL in MS and that serum levels of BAFF and APRIL do not reflect CSF levels.

Valproate induces epigenetic modifications in lymphomonocytes from epileptic patients.

Valproate (VPA) is an anti-epileptic and mood-stabilizing drug with a broad range of action and which mechanism of action still remains in part elusive. Recently the discovery that VPA modifies the epigenome increasing the transcriptional rate of target genes raises the issue of understanding the exact role of this mechanism. In this work we tested the possibility that VPA could modify the epigenome of lymphomonocytes (PBMC) obtained from epileptic patients chronically treated in monotherapy with VPA and phenobarbital. Acetyl-histone H3 expression was assessed by western blotting and global DNA methylation by incorporation of [³H]dCTP. A significant increase in histone acetylation and a correlated decrease of global DNA methylation were shown at VPA therapeutically relevant plasma concentrations. This effect was drug-related, since it was not demonstrated in PBMC obtained from phenobarbital-treated patients. Moreover, a VPA dose-response curve was performed on PBMC obtained from healthy controls, demonstrating an increase of acetyl-histone H3 content. We suggest that the epigenetic properties of VPA expressed on PBMC at these concentrations might be operative in different tissues, with possible implications for the field of neuropsychiatric disorders.

Adult-Onset Epilepsy in Presymptomatic Alzheimer’s Disease: A Retrospective Study

BACKGROUND The prevalence of epilepsy with onset in adulthood increases with age, mainly due to the accumulation of brain damage. However, a significant proportion of patients experience seizures of unknown cause. Alzheimers disease (AD) is associated with an increased risk of seizures. Seizure activity is interpreted as a secondary event related to hyperexcitability caused by amyloid-β aggregation. OBJECTIVE Since neurodegenerative processes begin several years before clinical symptoms, epilepsy could be more frequent in the presymptomatic stages of dementia. METHODS We retrospectively reviewed the prevalence of epilepsy of unknown origin with adult onset before cognitive decline in a large cohort of AD patients (EPS-AD) recruited based on clinical and neuropsychological data. Data of patients with epilepsy followed by AD were compared with two control groups: patients with AD without seizures (no EPS-AD) and a large reference population (RP). RESULTS In AD patients, the prevalence of epilepsy of unknown origin, with onset in the adulthood before cognitive decline is 17.1 times higher compared with the RP (95% CI: 10.3-28.3). In EPS-AD, seizures begin on average 4.6 years (median 2.0) before the onset of cognitive symptoms and cognitive decline starts 3.6 years earlier compared with noEPS-AD. CONCLUSIONS Neurodegenerative processes of dementia could play a key role in the pathogenesis of epilepsy in a subgroup of individuals intended to develop cognitive decline. Adult-onset epilepsy of undefined cause could thus represent a risk factor for the ongoing neurodegenerative damage, even preceding by years the onset of clinical symptoms of dementia.