Myeloid Sulf Deletion and Immune Dysfunction in Multiple Sulfatase Deficiency
Authors: Whitehead Anna K. , Yue Xinping 
Published: May 2022

Introduction

Multiple sulfatase deficiency (MSD) is a rare autosomal recessive disease due to pathogenic mutations in the sulfatase‐modifying factor 1 (SUMF1) gene. SUMF1 encodes the formylglycine‐generating enzyme responsible for an activating posttranslational modification of all sulfatases (17 in humans), and deficiency in these sulfatases results in accumulation of sulfated sugars, lipids, and steroids. The heparan sulfate (HS) 6‐O‐endosulfatases, commonly referred to as the Sulfs (Sulf1 and Sulf2), are among the sulfatases affected by SUMF1mutation. Unlike other sulfatases which degrade sulfated molecules in lysosomes, the Sulfs remodel the 6‐O‐sulfation status of HS outside of cells and thus modulate the functions of HS binding growth factors and cytokines. Although the systemic symptoms of MSD can be variable due to varying degrees of deficiency across all sulfatases, common features of MSD include hepatosplenomegaly and recurrent pneumonia. As HS has been shown to play important regulatory roles in host immunity, the objective of the current study was to investigate the role of the Sulfs in myeloid lineage development and function and to examine how myeloid Sulf deficiency contributes to the symptomatology of MSD.

Methods

To generate a mouse model with myeloid specific deletion of the Sulfs, we crossed Sulf1 and Sulf2 double floxed mice with mice carrying the Cre recombinase under control of lysozyme 2 (Lyz2‐cre). The role of the Sulfs in macrophage function was examined both in vitro in bone marrow derived macrophages and in vivo using the lipopolysaccharide (LPS) lung injury and inflammation model. Finally, Western blotting was performed to evaluate how myeloid Sulf deficiency alters transforming growth factor (TGF)‐β signaling.

Results

The myeloid specific Sulf deficient mice had enlarged spleens (231.0 ± 51.1 mg) compared to the control mice (Lyz2‐cre+/‐ alone with wildtype Sulfs, 95.4 ± 7.0 mg, P = 0.039), and some (5‐10%) died prematurely. Bone marrow derived macrophages from myeloid Sulf deficient mice exhibited increased proliferation but reduced ability to phagocytose Escherichia Coli (E. Coli) in vitrocompared to the control macrophages. Following intratracheal LPS (0.1 mg/kg) challenge (4 hours), myeloid Sulf deficient mice had significantly less neutrophils (1.8x105 ± 0.6x105cells) in the bronchoalveolar lavage fluid (BALF) compared to the control mice (6.3x105± 1.0x105cells, P = 0.0076). In contrast, coadministration of recombinant Sulf2 with LPS in wildtype mice lead to greater neutrophil recruitment in the airspace. Finally, enhanced phosphorylation of Smad2/3 (TGF‐β signal transducers) was found in spleens and lungs from myeloid specific Sulf deficient mice compared to the controls.

Conclusion

Our study reveals several important findings: the Sulfs play important roles in myeloid lineage development and function, myeloid Sulf deficiency contributes to the immune dysregulation observed in MSD, and enhanced TGF‐β signaling in the absence of the Sulfs might be responsible for the immune abnormality observed in myeloid Sulf deficient mice and in MSD. Our study builds on the foundation for targeting HS or the Sulfs in the treatment of MSD and potentially other myeloproliferative pathologies.