TLR-2 agonist Pam3CSK4 has no therapeutic effect on visceral leishmaniasis in BALB/c mice and may enhance the pathogenesis of the disease

TLR2 promotes traumatic deep venous thrombosis of the lower extremity following femoral fracture by activating the NF‑κB/COX‑2 signaling pathway in rats

Endothelial cells (ECs) are crucial for maintaining the integrity of blood vessel walls and reducing thrombosis. Deep venous thrombosis (DVT) is a common thrombotic disease and its diagnosis and treatment remain at the stage of coagulation function examination and post-onset treatment. Thus, identifying the pathogenesis of DVT is important. The present study investigated the significance of the Toll-like receptor 2 (TLR2)/nuclear factor kappa B (NF-κB)/cyclooxygenase-2 (COX-2) signaling pathway in a human umbilical vein EC (HUVECs) oxygen glucose deprivation (OGD) model and femoral fractures were induced in anesthetized rats using a quantifiable impact device delivering 5 J of energy to each side of the proximal outer thigh, followed by external fixation with a hip spica cast to create a traumatic deep venous thrombosis (TDVT) animal model. Rats were subjected to quantitative impact fixation to establish a TDVT model. The rats were treated with a TLR2 agonist (Pam3CSK4) and a TLR2 inhibitor (C29) via intraperitoneal injection and thrombus formation was examined. HUVECs were subjected to OGD and treated with Pam3CSK4 or C29 and cell viability and apoptosis were assessed. Western blotting, immunofluorescence and reverse transcription-quantitative PCR were used to examine the inflammatory responses and signaling pathways. In vivo experiments showed that Pam3CSK4 promoted thrombus formation and increased the mRNA and protein expression of NF-κB, COX-2, Tissue factor (TF), IL-6 and P-selectin compared with the model and C29 groups. In vitro experiments showed that Pam3CSK4 treatment resulted in a higher number of apoptotic cells than C29 treatment and that it increased the levels of NF-κB, COX-2, IL-6 and P-selectin, whereas C29 decreased them. Thus, TLR2 promotes the inflammatory response in EC through the NF-κB/COX-2 signaling pathway, which may lead to EC apoptosis and the occurrence of TDVT.

Transcriptomic profiling revealed immune-related signaling pathways in response to experimental infection of Leishmania donovani in two desert lizards from Northwest China

Little is known about the immune response of lizards to Leishmania parasties. In this study, we conducted the first liver transcriptome analysis of two lizards (Phrynocephalus przewalskii and Eremias multiocellata) challenged with L. donovani, endemic to the steppe desert region of northwestern China. Our results revealed that multiple biological processes and immune-related signaling pathways are closely associated with the immune response to experimental L. donovani infection in the two lizards, and that both lizards show similar changes to mammals in terms of immunity to Leishmania. However, the interspecific divergence of the two lizards leads to different transcriptomic changes. In particular, in contrast to P. przewalskii, the challenged E. mutltiocellata was characterized by the induction of down-regulation of most DEGs. These findings will contribute to the scarce resources on lizard immunity and provide a reference for further research on immune mechanisms in reptiles.

LdCyPA attenuates MAPK pathway to assist Leishmania donovani immune escape in host cells

BACKGROUND

Visceral leishmaniasis is a neglected tropical disease affecting millions of people worldwide. Macrophages serve as the primary host cells for L. donovani, the immune response capability of these host cells is crucial for parasites' intracellular survival. L. donovani peptidyl-prolyl cis/trans isomerase Cyclophilin A (LdCypA) is a key protein for L. donovani intracellular proliferation, while the molecular mechanism conducive to intracellular survival of parasites remains elusive.

METHODS

In this study, we generated a macrophage cell line overexpressing LdCyPA to investigate its role in controlling host immunity and promoting intracellular immune escape of L. donovani.

RESULTS

It was discovered that the overexpression of the LdCyPA cell line regulated the host immune response following infection by downregulating the proportion of M1-type macrophages, promoting the secretion of the anti-inflammatory factor IL-4, and inhibiting the secretion of pro-inflammatory factors like IL-12, IFN-γ, TNF-α, and INOS. Transcriptome sequencing and mechanistic validation, meanwhile, demonstrated that cells overexpressing LdCyPA controlled the immune responses that followed infection by blocking the phosphorylation of P38 and JNK1/2 proteins in the MAPK signaling pathway and simultaneously increasing the phosphorylation of ERK proteins, which helped the L. donovani escape immune recognition.

CONCLUSION

Our findings thus pave the way for the development of host-directed antiparasitic drugs by illuminating the pro-Leishmania survival mechanism of L. donovani cyclophilin A and exposing a novel immune escape strategy for L. donovani that targets host cellular immune regulation.