Mycobacteria Exploit Host Hyaluronan for Efficient Extracellular Replication

Abstract

In spite of the importance of hyaluronan in host protection against infectious organisms in the alveolar spaces, its role in mycobacterial infection is unknown. In a previous study, we found that mycobacteria interact with hyaluronan on lung epithelial cells. Here, we have analyzed the role of hyaluronan after mycobacterial infection was established and found that pathogenic mycobacteria can grow by utilizing hyaluronan as a carbon source. Both mouse and human possess 3 kinds of hyaluronan synthases (HAS), designated HAS1, HAS2, and HAS3. Utilizing individual HAS-transfected cells, we show that HAS1 and HAS3 but not HAS2 support growth of mycobacteria. We found that the major hyaluronan synthase expressed in the lung is HAS1, and that its expression was increased after infection with Mycobacterium tuberculosis. Histochemical analysis demonstrated that hyaluronan profoundly accumulated in the granulomatous legion of the lungs in M. tuberculosis-infected mice and rhesus monkeys that died from tuberculosis. We detected hyaluronidase activity in the lysate of mycobacteria and showed that it was critical for hyaluronan-dependent extracellular growth. Finally, we showed that L-Ascorbic acid 6-hexadecanoate, a hyaluronidase inhibitor, suppressed growth of mycobacteria in vivo. Taken together, our data show that pathogenic mycobacteria exploit an intrinsic host-protective molecule, hyaluronan, to grow in the respiratory tract and demonstrate the potential usefulness of hyaluronidase inhibitors against mycobacterial diseases.

c-Maf–Dependent Growth of Mycobacterium tuberculosis in a CD14hi Subpopulation of Monocyte-Derived Macrophages

“…HAS1 has a c-Maf binding site in its promoter region, c-Maf siRNA inhibits HAS1 expression, and HAS1 siRNA reduces growth of M. tuberculosis H37Rv in CD14 hi monocytes, suggesting that c-Maf regulates intracellular growth of M. tuberculosis in part through HAS1. The latter is an enzyme that controls production of hyaluronan, an abundant component of the extracellular matrix that can be broken down by mycobacterial hyaluronidases and used as a carbon source to enhance extracellular replication of M. tuberculosis (15). Hyaluronan is also present in the cytoplasm (34), and we found that HAS1 expression was markedly upregulated in M. tuberculosis H37Rv-infected CD14 hi cells but not in CD14 lo CD16 + monocytes.…”

“…Of these genes, 22 have c-Maf binding site in their promoter region. Among these genes, we selected that encoding HAS1, which was shown to enhance extracellular growth of M. tuberculosis H37Rv in the lungs (15). We also selected ZIP5 and TTC22, which are highly expressed in CD14 hi monocytes after stimulation with M. tuberculosis H37Rv.…”

“…Alternatively, hyaluronan fragments can induce formation of immunosuppressive macrophages (35) that may allow more rapid replication of M. tuberculosis. Hyaluronan and HAS1 are both present in the lungs of M. tuberculosis-infected mice and rhesus monkeys (15), suggesting that they contribute to the pathogenesis of tuberculosis in vivo. + MDMs from five healthy donors were cultured in medium alone or infected with GFP-expressing M. tuberculosis H37Rv, as outlined in Materials and Methods.…”

A Polysaccharide Lyase from Stenotrophomonas maltophilia with a Unique, pH-regulated Substrate Specificity

“…4). As mentioned before, secreted bacterial hyaluronan lyases have been shown to act as spreading factors to enhance invasion through degrading the host extracellular matrix as well as act as metabolic enzymes capable of generating sugars from host HA to promote bacterial growth during deep tissue infections (14). Alternatively, one recent study of the biofilm composition of two mucoid S. maltophilia strains isolated from cystic fibrosis patients identified a unique structure comprised of D-lactate-substituted, O-acetylated GalA and GlcA blocks (68).…”

“…In particular, HA lyases secreted by Group A Streptococcus are thought to act as spreading factors, enabling bacteria and toxins to disseminate throughout the host by degrading the high molecular weight HA present in the extracellular matrix (13). In Mycobacterium tuberculosis, secreted HA lyases generate low molecular weight sugars from HA that serve as carbon source for bacteria to replicate in deep tissue infections (14). In the case of P. aeruginosa biofilm formation, the periplasmic alginate lyase AlgL regulates the chain length and concentration of alginate in the periplasm during secretion (15).…”