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Amyloid plaque deposition and axonal degeneration are early events in AD pathogenesis. Aβ disrupts microtubules in presynaptic dystrophic neurites, resulting in the accumulation of impaired endolysosomal and autophagic organelles transporting β-site amyloid precursor protein cleaving enzyme (BACE1). Consequently, dystrophic neurites generate Aβ42 and significantly contribute to plaque deposition. Farnesyltransferase inhibitors (FTIs) have recently been investigated for repositioning toward the treatment of neurodegenerative disorders and block the action of farnesyltransferase (FTase) to catalyze farnesylation, a post-translational modification that regulates proteins involved in lysosome function and microtubule stability. In postmortem AD brains, FTase and its downstream signaling are upregulated. However, the impact of FTIs on amyloid pathology and dystrophic neurites is unknown. We tested the effects of the FTIs LNK-754 and lonafarnib in the 5XFAD mouse model of amyloid pathology. In 2-month-old 5XFAD mice treated chronically for 3 months, LNK-754 reduced amyloid plaque burden, tau hyperphosphorylation, and attenuated the accumulation of BACE1 and LAMP1 in dystrophic neurites. In 5-month-old 5XFAD mice treated acutely for 3 weeks, LNK-754 reduced dystrophic neurite size and LysoTracker-Green accumulation in the absence of effects on Aβ deposits. Acute treatment with LNK-754 improved memory and learning deficits in hAPP/PS1 amyloid mice. In contrast to LNK-754, lonafarnib treatment was less effective at reducing plaques, tau hyperphosphorylation and dystrophic neurites, which could have resulted from reduced potency against FTase compared to LNK-754. We investigated the effects of FTIs on axonal trafficking of endolysosomal organelles and found that lonafarnib and LNK-754 enhanced retrograde axonal transport in primary neurons, indicating FTIs could support the maturation of axonal late endosomes into lysosomes. Furthermore, FTI treatment increased levels of LAMP1 in mouse primary neurons and in the brains of 5XFAD mice, demonstrating that FTIs stimulated the biogenesis of endolysosomal organelles. We show new data to suggest that LNK-754 promoted the axonal trafficking and function of endolysosomal compartments, which we hypothesize decreased axonal dystrophy, reduced BACE1 accumulation and inhibited amyloid deposition in 5XFAD mice. Our results agree with previous work identifying FTase as a therapeutic target for treating proteinopathies and could have important therapeutic implications in treating AD. Show less

Hypertriglyceridemia is the most frequent and limiting adverse effect of bexarotene therapy in cutaneous T-cell lymphoma (CTCL). Despite standard prophylactic measures, there is a wide variability in the severity of this complication, which could be associated with both genetic and environmental factors. To analyze the association between genetic polymorphisms of apolipoprotein genes APOA5, APOC3, and APOE and the severity of hypertriglyceridemia during bexarotene therapy and to optimize patient selection for bexarotene therapy based on adverse effect profile. This case series study was conducted in 12 university referral hospitals in Spain from September 17, 2014, to February 6, 2015. One hundred twenty-five patients with a confirmed diagnosis of CTCL who had received bexarotene therapy for at least 3 months were enrolled. Nine patients were excluded owing to missing analytic triglyceride level data, leaving a study group of 116 patients. Data on demographic and cardiovascular risk factor were collected, and a complete blood analysis, including lipid profile and genetic analysis from a saliva sample, was performed. Primary outcomes were the maximal triglyceride levels reported in association with the minor alleles of the polymorphisms studied. Among 116 patients, the mean (SD) age was 61.2 (14.7) years, 69 (59.5%) were men, and 85 (73.2%) had mycosis fungoides, the most prevalent form of CTCL. During bexarotene therapy, 96 patients (82.7%) experienced hypertriglyceridemia, which was severe or extreme in 8 of these patients (8.3%). Patients who carried minor alleles of the polymorphisms did not show significant differences in baseline triglyceride concentrations. After bexarotene treatment, carriers of at least 1 of the 2 minor alleles of APOA5 c.-1131T>C and APOC3 c.*40C>G showed lower levels of triglycerides than noncarriers (mean [SD], 241.59 [169.91] vs 330.97 [169.03] mg/dL, respectively; P = .02). These results indicate that the screening of APOA5 and APOC3 genotypes may be useful to estimate changes in triglyceride concentrations during bexarotene treatment in patients with CTCL and also to identify the best candidates for bexarotene therapy based on the expected adverse effect profile. Show less