Role of succinyl substituents in the mannose-capping of lipoarabinomannan and control of inflammation in Mycobacterium tuberculosis infection.

The covalent modification of bacterial (lipo)polysaccharides with discrete substituents may impact their biosynthesis, export and/or biological activity. Whether mycobacteria use a similar strategy to control the biogenesis of its cell envelope polysaccharides and modulate their interaction with the host during infection is unknown despite the report of a number of tailoring substituents modifying the structure of these glycans. Here, we show that discrete succinyl substituents strategically positioned on Mycobacterium tuberculosis (Mtb) lipoarabinomannan govern the mannose-capping of this lipoglycan and, thus, much of the biological activity of the entire molecule. We further show that the absence of succinyl substituents on the two main cell envelope glycans of Mtb, arabinogalactan and lipoarabinomannan, leads to a significant increase of pro-inflammatory cytokines and chemokines in infected murine and human macrophages. Collectively, our results validate polysaccharide succinylation as a critical mechanism by which Mtb controls inflammation.

An Uncommon Culprit: Trapezius Dystonia as a Cause of Thoracic Outlet Syndrome: A Case Report.

Thoracic outlet syndrome (TOS) results from compression of the neurovascular bundle in the thoracic outlet. Several etiologies can contribute to the development of thoracic outlet syndrome, including both congenital and acquired causes. Historically, trapezius pathology has not been considered a cause of TOS; however, here we report a patient with neurogenic TOS plus ipsilateral trapezius hypertonicity and hypertrophy who had significant symptomatic improvement following botulinum toxin injections to trapezius.