No abstract

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, contaminating in a wide variety of foods and feeds. Mycotoxins, including OTA, could cause immunosuppression in almost all previous studies in vivo. However, the vast majority of results in vitro showed that mycotoxins caused immunostimulation. Why the results of studies in vitro are contrary to studies in vivo is unknown. Our study aims to explore the underlying reason and mechanism of the paradoxical effect. In this study, porcine alveolar macrophage cell line 3D4/21 was chosen as an in vitro model and treated with 1.0 μg/mL OTA for different times. Some indexes, such as expression of inflammatory cytokines, migration, phagocytosis, macrophage polarization, autophagy-related proteins, and Akt1 phosphorylation, were detected. The results showed that pro-inflammatory cytokine expression, migration, and phagocytosis were increased, with macrophage polarization to the M1 phenotype at 24 h of OTA exposure. Surprisedly, anti-inflammatory cytokine expression was increased, cell phagocytosis and migration were decreased, and macrophage polarization was switched from M1 to M2 at 72 h of OTA exposure. Furthermore, we found that long-time exposure of OTA also suppressed autophagy, and the autophagy activator blocked the OTA-induced immunosuppression. Phosphorylation of Akt1 plays a positive role in autophagy inhibition. In conclusion, long-time instead of shorttime exposure of OTA in vitro induced immunosuppression. The immunosuppression mechanism of OTA in vitro involved inhibition of autophagy through upregulating p-Akt1. Our results provide new insight into research on the mechanism of mycotoxin-induced immunosuppression in vitro.

Porcine circovirus type 2 (PCV2) is an important pathogen in swine herds. We previously reported that glutamine (Gln) deficiency promoted PCV2 infection in vitro. Here, we established a Gln deficiency model in vivo and further investigated the detailed molecular mechanisms. In vivo and in vitro, Gln deficiency promoted PCV2 infection, which was evident through increased viral yields and PCV2 Cap protein synthesis. It also induced autophagy, as demonstrated by the increases in LC3-II conversion, SQSTM1 degradation, and GFP-LC3 dot accumulation. Autophagy inhibition abolished the effects of Gln deficiency on PCV2 infection. Inhibition of ROS generation alleviated the Gln deficiency-activated JAK2/STAT3 signaling pathway, thereby inhibiting autophagy induction. In vitro, the inhibition of STAT3 by an inhibitor or RNA interference blocked autophagy, thus reversing the effects of Gln deficiency on PCV2 infection. These results indicate that Gln deficiency activates autophagy by upregulating ROS-medicated JAK2/STAT3 signaling and thereby promoting PCV2 infection.

Mastitis is mainly induced by gram-negative bacterial infections, causing devastating economic losses to the global cattle industry. Both selenium (Se) and taurine (Tau) exhibit multiple biological effects, including reducing inflammation. However, no studies have reported the protective effect of the combined use of Se and Tau against mastitis, and the underlying mechanisms remain unclear. In this study, lipopolysaccharide (LPS), the vital virulence factor of gram-negative bacteria, was used to construct the in vivo and vitro mastitis models. The results of in vivo model showed that Se and Tau combination was more effective than either substance alone in reducing tissue hyperemia, edema, and neutrophil infiltration in the mammary acinar cavity, improving the blood-milk barrier in LPS-induced mice mastitis, and decreasing the expression of proinflammatory factors and the activity of MPO. Moreover, Se and Tau combination significantly increased the levels of LPS-induced reduction in PI3K/Akt/mTOR, but the expressions of TLRs and NLRP3 were not significantly changed in the mammary tissue. In the in vitro experiments, the effects of Se and Tau combination or alone on inflammatory factors, inflammatory mediators, MPO activity, and blood-milk barrier were consistent with those in vivo. The Se and Tau combination has also been found to increase the survival rate of BMECs compared with each substance alone via promoting cellular proliferation and inhibiting apoptosis. Also, it has been confirmed that this combination could restore the LPS-induced inhibition in the PI3K/Akt/mTOR signaling pathway. Inhibition of mTOR by Rapamycin counteracted the combined protection of SeMet and Tau against LPS-induced inflammatory damage, the inhibition of PI3K by LY294002 blocked the activation of mTOR, and the accumulation of ROS by the ROS agonist blocked the activation of PI3K. In conclusion, these findings suggested that Se and Tau combination was better than either substance alone in protecting LPS-induced mammary inflammatory lesions by upregulating the PI3K/Akt/mTOR signaling pathway.

The Qiangtang Mesozoic sedimentary basin is a new field of hydrocarbon exploration, in which the Buqu Formation dolostone reservoirs have attracted increasing attention in recent years. To determine the origin of these reservoirs, petrographic study, fluid inclusion thermometry dating, and C-O and Sr isotopic dating were performed. The results revealed the genesis and evolution of different types of dolomite matrix and cement, as follows: 1) The dolomite texture in the study area is closely related to its formation environment and process and can be categorized as primary fabric well-preserved dolomite (Rd1), primary fabric poorly-preserved dolomite, and dolomite filling. The primary fabric-poorly-preserved dolomite includes fine-grained euhedral dolomite (Rd2), fine-grained planar subhedral dolomite (Rd3), and medium-to coarse-grained anhedral dolomite (Rd4). The dolomite filling includes fine-grained planar subhedral cave-filling dolomite (Cd1) and medium-to coarse-grained anhedral, saddle dolomite (Cd2). 2) Rd1 has δ13C‰PDB of 3.42‰–4.23‰, δ18O‰PDB from −4.22‰ to −3.37‰, and 87Sr/86Sr of 0.707654–0.708176 and was formed in the contemporaneous or penecontemporaneous stage at low temperatures by mimic replacement related to seawater evaporation. Abundant supersaturated dolomitization fluids favored the preservation of its primary dolomite texture. 3) Rd2 has δ13C‰PDB of 3.18‰–4.11‰, δ18O‰PDB from −4.56‰ to −4.23‰, and 87Sr/86Sr (0.707525–0.708037), while Rd3 has δ13C‰PDB of 2.72‰–4.42‰, δ18O‰PDB from −6.57‰ to −5.56‰, and 87Sr/86Sr of 0.707432–0.707990. Both were formed at low temperatures in the shallow-burial stage, when the dolomitization fluid was mainly derived from seawater. Excessive dolomitization during the late shallow-burial stage caused the destruction of the dolomite crystals from euhedral to subhedral. 4) Rd4 has δ13C‰PDB of 3.24‰–4.14‰, δ18O‰PDB from −8.22‰ to −6.37‰, and 87Sr/86Sr of 0.707234–0.707884 and resulted from dolomitization or recrystallization at high temperatures in the medium-to deep-burial stage. The crystal curvature was caused by high environmental temperatures. 5) Cd1 has δ13C‰PDB of 3.02‰, δ18O‰PDB of −5.13‰, and 87Sr/86Sr of 0.708147 and was formed during cavern filling before the shallow-burial stage. Cd2 has δ13C‰PDB of −0.09‰−3.38‰, δ18O‰PDB from −10.41‰ to −8.56‰, and 87Sr/86Sr of 0.708180–0.708876 and was related to the collisional orogeny between the Lhasa termite and the Qiangtang Basin in the late Early Cretaceous. Fluids in the overlying and underlying clastic strata of the Buqu Formation were driven by the thermal hot spot during compressional tectonic setting. These fluids caused negative shifts in the oxygen isotope compositions of the earlier dolomite.