Acid sphingomyelinase deficiency (Niemann‒Pick disease Type B) as an inflammatory disease

Interstitial lung disease in lysosomal storage disorders

Lysosomes are intracellular organelles that are responsible for degrading and recycling macromolecules. Lysosomal storage diseases (LSDs) are a group of inherited diseases caused by mutations affecting genes that encode the function of the lysosomal enzymes. Three LSDs are associated with lung involvement and/or interstitial lung disease (ILD): Gaucher disease (GD); Niemann-Pick disease, also known as acid sphingomyelinase deficiency (ASMD); and Fabry disease (FD). In GD and in ASMD, analysis of bronchoalveolar lavage fluid and lung biopsy can be informative, showing foamy cells. In GD, ILD is rare. Enzyme replacement therapy (ERT) has been available since 1991 and has greatly changed the natural history of GD, with pulmonary failure and death reported before the ERT era. In ASMD, ILD is frequent and is usually associated with spleen enlargement, low platelet cell count and low level of high-density lipoprotein-cholesterol. Results of ERT are promising regarding preliminary results of olipudase alfa in paediatric and adult ASMD populations. The most frequent respiratory manifestation in FD is COPD-like symptoms regardless of smoking habit and dyspnoea due to congestive heart failure. Early diagnosis of these three LSDs is crucial to prevent irreversible organ damage. Early initiation of ERT can, at least in part, prevent organ failure.

Acid sphingomyelinase/ceramide mediates structural remodeling of cerebral artery and small mesenteric artery in simulated weightless rats

AIMS

Weightlessness exposure conduces to substantial vascular remodeling, mechanisms behind which remain unclear. Acid sphingomyelinase (ASM) catalyzed ceramide (Cer) generation accounts for multiple vascular disorders, so the role of it in adjustment of cerebral artery (CA) and small mesenteric artery (MA) was investigated in simulated weightless rats.

MAIN METHODS

Rats were hindlimb unloaded tail suspended (HU) to simulate the effect of weightlessness. Arterial morphology was examined by hematoxylin-eosin staining. Cer abundance was measured by immunohistochemistry. Western blotting was used to detect protein content. Apoptosis was detected by transferase-mediated dUTP nick end labeling.

KEY FINDINGS

During 4 weeks of tail suspension, intima-media thickness (IMT) and media cross section area (CSA) were increased gradually in CA but decreased gradually in MA (P < 0.05). Correspondingly, the apoptosis and proliferation of vascular smooth muscle cells were reduced and enhanced respectively in CA (P < 0.05), while promoted and restrained in MA (P < 0.05). As compared to control, both ASM protein expression and Cer content were lowered in CA and elevated in MA of HU rats (P < 0.05). Permeable Cer incubation reversed the change of apoptosis and proliferation in CA of HU rats, while ASM inhibition recapitulated it in control rats. On the contrary, ASM inhibitors restored the alteration of apoptosis and proliferation in MA of HU.

SIGNIFICANCE

The results suggest that by controlling the balance between apoptosis and proliferation, ASM/Cer exerts an important role in structural adaptation of CA and MA to simulated weightlessness.

Respiratory impairment in Niemann-Pick B disease: Two case reports and review for the pulmonologist

Acid sphingomyelinase deficiency (ASMD), also called Niemann-Pick disease, is a storage disorder with pulmonary involvement but few respiratory symptoms in adults. However, the disease may evolve towards clinically relevant respiratory symptoms with referral to the pulmonologist for management and care. Based on two case reports illustrating respiratory impairment, the aim of this work was to review clinical features, diagnosis, respiratory prognostic and therapeutics for the pulmonologist. Overall, storage disorder should be suspected in the presence of hepatosplenomegaly and interstitial lung disease. Concomitant thrombopenia or hyperlipidemia should also draw attention. Following recent consensus guidelines, diagnosis is based on enzyme assay for ASM activity in blood, with subsequent gene sequencing once the biochemical diagnosis has been confirmed. Disease is slowly progressive and the main causes of death are respiratory and liver failure. Presence of emphysema lesions or worsening of respiratory symptoms should call for the intensification of treatment. Though enzyme replacement therapy is a promising way of development, lung transplantation might be considered for these patients in the absence of contraindication.