Differential Roles of the Calcium Ion Channel TRPV4 in Host Responses to Mycobacterium tuberculosis Early and Late in Infection.

Mycobacterium tuberculosis subverts host immunity to proliferate within host tissues. Non-selective transient receptor potential (TRP) ion channels are involved in host responses and altered upon bacterial infections. Altered expression and localization of TRPV4 in macrophages upon virulent M. tuberculosis infection together with differential distribution of TRPV4 in human tuberculosis (TB) granulomas indicate a role of TRPV4 in TB. Compared with wild-type mice, Trpv4-deficient littermates showed transiently higher mycobacterial burden and reduced proinflammatory responses. In the absence of TRPV4, activation failed to render macrophages capable of controlling mycobacteria. Surprisingly, Trpv4-deficient mice were superior to wild-type ones in controlling M. tuberculosis infection in the chronic phase. Thus, Trpv4 is important in host responses to mycobacteria, although with opposite functions early versus late in infection. Ameliorated chronic infection in the absence of Trpv4 and its expression in human TB lesions indicate TRPV4 as putative target for host-directed therapy.

Multimodal X-ray imaging of nanocontainer-treated macrophages and calcium distribution in the perilacunar bone matrix.

Studies of biological systems typically require the application of several complementary methods able to yield statistically-relevant results at a unique level of sensitivity. Combined X-ray fluorescence and ptychography offer excellent elemental and structural imaging contrasts at the nanoscale. They enable a robust correlation of elemental distributions with respect to the cellular morphology. Here we extend the applicability of the two modalities to higher X-ray excitation energies, permitting iron mapping. Using a long-range scanning setup, we applied the method to two vital biomedical cases. We quantified the iron distributions in a population of macrophages treated with Mycobacterium-tuberculosis-targeting iron-oxide nanocontainers. Our work allowed to visualize the internalization of the nanocontainer agglomerates in the cytosol. From the iron areal mass maps, we obtained a distribution of antibiotic load per agglomerate and an average areal concentration of nanocontainers in the agglomerates. In the second application we mapped the calcium content in a human bone matrix in close proximity to osteocyte lacunae (perilacunar matrix). A concurrently acquired ptychographic image was used to remove the mass-thickness effect from the raw calcium map. The resulting ptychography-enhanced calcium distribution allowed then to observe a locally lower degree of mineralization of the perilacunar matrix.

M. tuberculosis-Induced Necrosis of Infected Neutrophils Promotes Bacterial Growth Following Phagocytosis by Macrophages.

Neutrophils represent the main infected cell population in the lungs of active tuberculosis patients. Efficient removal of infected and dying neutrophils is required to protect the surrounding tissue from bioactive neutrophil molecules and subsequent pathological sequelae. While the removal of apoptotic M. tuberculosis (Mtb)-infected cells, or efferocytosis, is considered beneficial for host defense, little is known about Mtb-infected necrotic neutrophils. We found that Mtb induces necrosis of human neutrophils in an ESX-1-dependent manner, and neutrophil-produced reactive oxygen species (ROS) drive this necrosis. Neutrophil necrosis was required for Mtb growth after uptake of infected neutrophils by human macrophages. Pharmacological inhibition of ROS production could prevent necrosis and restore the capability of macrophages to control Mtb growth, thereby identifying a potential host-directed therapy target. Taken together, necrosis represents the starting point for a vicious cycle including the uptake of infected necrotic cells by other phagocytes, Mtb growth therein, and sustained infection.

Isoniazid@Fe2 O3 Nanocontainers and Their Antibacterial Effect on Tuberculosis Mycobacteria.

Isoniazid-filled Fe2 O3 hollow nanospheres (INH@Fe2 O3 , diameter <30 nm, 48 wt % INH-load) are prepared for the first time and suggested for tuberculosis therapy. After dextran-functionalization, the INH@Fe2 O3 @DEX nanocontainers show strong activity against Mycobacterium tuberculosis (M.tb.) and M.tb.-infected macrophages. The nanocontainers can be considered as "Trojan horses" and show efficient, active uptake into both M.tb.-infected macrophages and even into mycobacterial cells.