The PPE2 protein of Mycobacterium tuberculosis is secreted during infection and facilitates mycobacterial survival inside the host

Mycobacterium tuberculosis secrets various effector proteins to evade host immune responses for facilitating its intracellular survival. The bacterial genome encodes several unique PE/PPE family proteins, which have been implicated to play important role in mycobacterial pathogenesis. A member of this family, PPE2 have been shown to contain a monopartite nuclear localization signal (NLS) and a DNA binding domain. In this study, we demonstrate that PPE2 protein is present in the sera of mice infected with either M. smegmatis expressing PPE2 or a clinical strain of M. tuberculosis (CDC1551). It was found that exogenously added PPE2 can permeate through the macrophage cell membrane and eventually translocate into the nucleus which requires the presence of NLS which showed considerable homology to HIV-tat like cell permeable peptides. Exogenously added PPE2 could inhibit NO production and decreased mycobacterial survival in macrophages. PPE2-null mutant of M. tuberculosis failed to inhibit NO production and had poor survival in macrophages which could be rescued by complementation with full-length PPE2. PPE2-null mutants also had poor survival in the lungs of infected mice indicating that PPE2 even when present in the bloodstream can confer a survival advantage to mycobacteria.

The Clinical Significance of iNOS/NO Signaling Pathway in Traumatic Shock and the Mechanism under the Promotion on the Development of Traumatic Shock via Endoplasmic Reticulum Stress

OBJECTIVE

This study aims to clarify the clinical significance of the inducible nitric oxide synthase (iNOs)/nitric oxide (NO) signaling pathway and endoplasmic reticulum stress (ERS) in traumatic shock (TS) and the mechanism of action, so as to offer a novel direction for the emergency treatment of TS in the future.

METHODS

The clinical data of 90 patients with TS treated in our hospital between June 2019 and January 2021 were retrospectively analyzed. Patients were divided into mild (n = 30), moderate (n = 30), and severe group (n = 30) based on their disease severity. Furthermore, patients were assigned into Groups A and B for fluid resuscitation based on a pulse index continuous cardiac output (PICCO) monitor and fluid resuscitation based on monitoring results of central venous pressure (CVP) and mean arterial pressure (MAP), respectively. Additionally, the 18 purchased Sprague Dawley (SD) rats were randomized into model (TS model), control (normal rats) and intervention (TS model injected with iNOS inhibitor) groups, with 6 rats each. iNOs and NO levels were measured by colorimetry, and the concentrations of inflammatory factors were quantified using enzyme-linked immunosorbent assays (ELISAs). Polymerase chain reaction (PCR) and western blot were adopted for the quantification of ERS markers (glucose-related protein 78 (GRP78), GRP94 and C/EBP homologous protein (CHOP)), and hematoxylin-eosin (HE) staining of rat cardiac tissue was carried out to observe the pathological state of myocardial tissue.

RESULTS

The moderate group showed higher levels of iNOS, NO, GRP78, GRP94 and CHOP than the mild group and lower levels of them than the severe group (all p < 0.05). MAP, extravascular lung water index (EVLWI), pulmonary vascular permeability index (PVPI), and locus control region (LCR) increased in both Groups A and B after resuscitation, with more significant increases of these parameters in Group A. The application of PICCO technique lowered the levels of iNOS, NO, inflammatory factors, GRP78, GRP94 and CHOP in TS patients. In addition, the intervention group had lower levels of iNOS, NO, inflammatory factors, GRP78, GRP94, and CHOP than the model group and higher levels of them than the control group. According to the results of HE staining of myocardial tissue, the intervention group had significantly alleviated myocardial necrosis than the model group, with slightly stained cytoplasm, visible contraction bands in most myocardium, and significantly reduced neutrophil infiltration.

CONCLUSIONS

iNOS/NO and ERS increase with the severity of TS, and PICCO can effectively lower their levels. The results of animal experiments suggest that the inhibition of iNOS/NO can relieve inflammation and ERS intensification, thus alleviating the progression of TS.

Dexmedetomidine protects against lipopolysaccharide-induced early acute kidney injury by inhibiting the iNOS/NO signaling pathway in rats

Increasing evidence has demonstrated that dexmedetomidine (DEX) possesses multiple pharmacological actions. Herein, we explored the protective effect and potential molecular mechanism of DEX on lipopolysaccharide (LPS)-induced early acute kidney injury (AKI) from the perspective of antioxidant stress. We found that DEX (30 μg/kg, i.p.) ameliorated the renal dysfunction and histopathological damage (tubular necrosis, vacuolar degeneration, infiltration of inflammatory cells and cast formation) induced by LPS (10 mg/kg). DEX also attenuated renal oxidative stress remarkably in LPS-induced early AKI, as evidenced by reduction in production of reactive nitrogen species, decreasing malondialdehyde levels, as well as increasing superoxide dismutase activity and glutathione content. DEX prevented activator protein-1 translocation, inhibited phosphorylation of I-kappa B (IκB) and activation of nuclear factor kappa B (NF-κB) in LPS-induced early AKI, as assessed by real-time quantitative polymerase chain reaction and protein levels of c-Jun, c-Fos, IκB and NF-κB. Notably, DEX pretreatment had the same effect as intraperitoneal injection of an inhibitor of inducible nitric oxide synthase inhibitor (1400W; 15 mg/kg), and inhibited the activity of renal inducible nitric oxide synthase (iNOS) and decreased the expression of iNOS mRNA and NO production. However, the protective effect of DEX on LPS-induced early AKI was reversed by the alpha 2 adrenal receptor (α₂-AR) inhibitor atipamezole, whereas the imidazoline receptor inhibitor idazoxan did not. Taken together, DEX protects against LPS-induced early AKI in rats by inhibiting the iNOS/NO signaling pathway, mainly by acting on α₂-ARs instead of IRs.

LPS potentiates nucleotide-induced inflammatory gene expression in macrophages via the upregulation of P2Y2 receptor

Sepsis is a severe systemic inflammatory response that is associated with high morbidity and mortality. A previous study using an animal model of sepsis showed that survival was significantly lower in WT mice than in P2Y(2) receptor (P2Y(2)R)-deficient mice, suggesting that P2Y(2)R plays a role in septic death. We therefore investigated the role of P2Y(2)R in the inflammatory responses of RAW264.7 murine macrophages to LPS. LPS time-dependently upregulated P2Y(2)R mRNA levels, with a prominent increase observed at 4 h. In addition, LPS increased ATP release in a time dependent manner (5-120 min post LPS treatment). Accordingly, we pretreated cells with LPS for 4 h to induce P2Y(2)R expression and then stimulated the cells with UTP or ATP for 16 h. Interestingly, ATP- or UTP-dependent P2Y(2)R activation in LPS-pretreated cells resulted in dramatically enhanced HMGB1 secretion, COX-2 and iNOS expression, and furthermore PGE2 and NO production compared to LPS treatment alone (4 h) or ATP or UTP treatment alone (16 h), an effect that was inhibited by P2Y(2)R silencing. In addition, these increases in HMGB1 secretion, COX-2 and iNOS expression and PGE(2) and NO production commonly involved the JNK, PKC and PDK pathways. Taken together, these data demonstrate that LPS-dependent upregulation of P2Y(2)R plays a critical role in facilitating the inflammatory responses induced by LPS.

Common bean (Phaseolus vulgaris L.) hydrolysates inhibit inflammation in LPS-induced macrophages through suppression of NF-κB pathways

The objectives of this study were to evaluate the antioxidant capacity of protein hydrolysates of the common bean (Phaseolus vulgaris L.) varieties Negro 8025 and Pinto Durango and determine their effect on the markers of inflammation in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Cell viability was determined and the percentage of viable cells was calculated and concentrations that allowed >80% cell viability were used to determine the markers of inflammation. Alcalase hydrolysates and pepsin-pancreatin hydrolysates showed the highest antioxidant capacity after 80 and 120min of hydrolysis, respectively. Alcalase hydrolysates of the common bean Pinto Durango at 120min inhibited inflammation, with IC50 values of 34.9±0.3, 13.9±0.3, 5.0±0.1 and 3.7±0.2μM, while var. Negro needed 43.6±0.2, 61.3±0.3, 14.2±0.3 and 48.2±0.1μM for the inhibition of cyclooxygenase-2 expression, prostaglandin E2 production, inducible nitric oxide synthase expression and nitric oxide production, respectively. Also, hydrolysates significantly inhibited the transactivation of NF-κB and the nuclear translocation of the NF-κB p65 subunit. In conclusion, hydrolysates from the common bean can be used to combat inflammatory and oxidative-associated diseases.