Human lipodystrophies linked to mutations in A-type lamins and to HIV protease inhibitor therapy are both associated with prelamin A accumulation, oxidative stress and premature cellular senescence

Abstract

Lipodystrophic syndromes associated with mutations in LMNA, encoding A-type lamins, and with HIV antiretroviral treatments share several clinical characteristics. Nuclear alterations and prelamin A accumulation have been reported in fibroblasts from patients with LMNA mutations and adipocytes exposed to protease inhibitors (PI). As genetically altered lamin A maturation also results in premature ageing syndromes with lipodystrophy, we studied prelamin A expression and senescence markers in cultured human fibroblasts bearing six different LMNA mutations or treated with PIs. As compared to control cells, fibroblasts with LMNA mutations or treated with PIs had nuclear shape abnormalities and reduced proliferative activity that worsened with increasing cellular passages. They exhibited prelamin A accumulation, increased oxidative stress, decreased expression of mitochondrial respiratory chain proteins and premature cellular senescence. Inhibition of prelamin A farnesylation prevented cellular senescence and oxidative stress. Adipose tissue samples from patients with LMNA mutations or treated with PIs also showed retention of prelamin A, overexpression of the cell cycle checkpoint inhibitor p16 and altered mitochondrial markers. Thus, both LMNA mutations and PI treatment result in accumulation of farnesylated prelamin A and oxidative stress that trigger premature cellular senescence. These alterations could participate in the pathophysiology of lipodystrophic syndromes and lead to premature ageing complications. LMNA-linked lipodystrophies and progeroid syndromes form a clinical continuum of related phenotypes. 2-8 Otherwise, HIV-infected patients receiving antiretroviral therapy frequently develop a lipodystrophy syndrome associated with a high risk of metabolic and cardiovascular complications. 9 These patients also face a growing number of other agerelated comorbidities, such as neurodegeneration, osteopenia and malignancies. 10 A-type lamins are nuclear proteins required for the structural and functional integrity of the nucleus. Lamin A is translated as a protein precursor that undergoes several maturation steps, including the addition of a C-terminal farnesyl residue, which is subsequently removed by proteolytic cleavage (reviewed by Mattout et al 1 ). Defective physiological maturation of prelamin A is the main pathophysiological mechanism underlying several premature ageing syndromes, including the Hutchinson-Gilford progeria syndrome (HGPS) (reviewed by Young et al 11 ). Several studies have convincingly demonstrated that the retention of the farnesylated residue confers toxic properties to the partially processed prelamin A. 11-13 Both cellular abnormalities [14][15][16][17] and premature ageing phenotype in mice 18 are significantly improved by using drugs that inhibit prelamin A farnesylation.

LMNA Mutations Induce a Non-Inflammatory Fibrosis and a Brown Fat-Like Dystrophy of Enlarged Cervical Adipose Tissue

“…13 Accordingly, the presence of prelamin A has been observed in lipoatrophic abdominal scAT from HIV-infected patients receiving a protease inhibitorbased therapeutic regimen. 11 We and others have previously reported the presence of mitochondrial abnormalities in cells and/or lipoatrophic adipose tissue from patients with LMNA mutations or HIV infection 11,14 -16 Moreover, patients with mutations in mitochondrial DNA (mtDNA)-encoded tRNA Lys can develop dorsocervical non-encapsulated fat masses, [17][18][19] which suggests that mitochondrial dysfunction could also have a role in LMNA-and HIV-linked lipodystrophies. Thus far, histologic features of LMNA-mutated scAT have not been reported, with the exception of an ultrastructural analysis that revealed nuclear alterations in some lipoatrophic adipocytes.…”

“…We and others have demonstrated that FPLD2 and metabolic laminopathies are associated with an abnormal accumulation of prelamin A, possibly due to misrecognition of the mutated protein by Zmpste24. 10,11 That LMNA mutations can lead to lipoatrophy in most scAT depots, but to lipohypertrophy in the faciocervical area, remains poorly understood but could be linked to differences in fat depot physiologic features. It has been suggested that prelamin A accumulation may elicit different effects in body fat areas, depending on the level of local activation of the adipogenic factor peroxisome proliferator-activated receptor-␥ (PPAR␥).…”

“…10 Partial lipodystrophies with peripheral lipoatrophy but increased cervical fat (buffalo hump) are also observed in HIV-infected patients receiving antiretroviral therapy, primarily the thymidine analogues nucleoside reverse transcriptase inhibitors and HIV protease inhibitors (reviewed in Caron-Debarle et al 12 ). Some protease inhibitors, in particular, ritonavir, widely used, can induce cellular prelamin A accumulation, 11 via direct inhibition of the zinc metallopeptidase Zmpste24. 13 Accordingly, the presence of prelamin A has been observed in lipoatrophic abdominal scAT from HIV-infected patients receiving a protease inhibitorbased therapeutic regimen.…”

MicroRNAs in hereditary and sporadic premature aging syndromes and other laminopathies

“…For example, they can have an iatrogenic origin, as in HIV patients treated with protease inhibitors. Most molecules of this class inhibit ZMPSTE24 function, resulting in the blockage of prelamin A maturation and its accumulation in nuclei, leading to clinical manifestations of lipodystrophy syndrome (Béréziat et al., 2011; Caron et al., 2007; Coffinier et al., 2008; Miranda et al., 2007). …”

Integrated High-Content Quantification of Intracellular ROS Levels and Mitochondrial Morphofunction

“…There is a subtle balance between the production and removal of the different ROS molecules to maintain their intracellular concentration at a physiological level. Any perturbation to this fragile steady-state that increases intracellular ROS provokes oxidative stress, a phenomenon associated with the natural aging process, as well as various multispectrum diseases including cancer and laminopathies (Harman 1956;Naderi et al 2006;Moylan and Reid 2007;Caron et al 2007;Salmon et al 2010;Sieprath et al 2012). …”