Biased agonism of protease-activated receptor-1 regulates thrombo-inflammation in murine sickle cell disease

Sickle cell disease (SCD) is a hereditary hemoglobinopathy marked by hemolytic anemia and vaso-occlusive events (VOE). Chronic endothelial activation, inflammation, and coagulation activation contribute to vascular congestion, VOE, and end-organ damage. Coagulation proteases like thrombin and activated protein C (APC) modulate inflammation and endothelial dysfunction by activating protease-activated receptor 1 (PAR1), a G-protein coupled receptor. Thrombin cleaves PAR1 at Arg41, while APC cleaves PAR1 at Arg46, initiating either pro-inflammatory or cytoprotective signaling, respectively, a signaling conundrum known as biased agonism. Our prior research established the role of thrombin and PAR1 in vascular stasis in an SCD mouse model. However, the role of APC and APC-biased PAR1 signaling in thrombin generation, inflammation and endothelial activation in SCD remains unexplored. Inhibition of APC in SCD mice increased thrombin generation, inflammation, and endothelial activation during both steady state and TNFα challenge. To dissect the individual contributions of thrombin-PAR1 and APC-PAR1 signaling, we employed transgenic mice with point mutations at two PAR1 cleavage sites, ArgR41Gln (R41Q) imparting insensitivity to thrombin and Arg46Gln (R46Q) imparting insensitivity to APC. Sickle bone marrow chimeras expressing PAR1-R41Q exhibited reduced thrombo-inflammatory responses compared to PAR1-WT or PAR1-R46Q mice. These findings highlight the potential benefit of reducing thrombin-dependent PAR1 activation while preserving APC-PAR1 signaling in SCD thromboinflammation. These results also suggest that pharmacological strategies promoting biased PAR1 signaling could effectively mitigate vascular complications associated with SCD.

The APC-EPCR-PAR1 axis in sickle cell disease

Sickle Cell Disease (SCD) is a group of inherited hemoglobinopathies. Sickle cell anemia (SCA) is caused by a homozygous mutation in the β-globin generating sickle hemoglobin (HbS). Deoxygenation leads to pathologic polymerization of HbS and sickling of erythrocytes. The two predominant pathologies of SCD are hemolytic anemia and vaso-occlusive episodes (VOE), along with sequelae of complications including acute chest syndrome, hepatopathy, nephropathy, pulmonary hypertension, venous thromboembolism, and stroke. SCD is associated with endothelial activation due to the release of danger-associated molecular patterns (DAMPs) such as heme, recurrent ischemia-reperfusion injury, and chronic thrombin generation and inflammation. Endothelial cell activation is mediated, in part, by thrombin-dependent activation of protease-activated receptor 1 (PAR1), a G protein coupled receptor that plays a role in platelet activation, endothelial permeability, inflammation, and cytotoxicity. PAR1 can also be activated by activated protein C (APC), which promotes endothelial barrier protection and cytoprotective signaling. Notably, the APC system is dysregulated in SCD. This mini-review will discuss activation of PAR1 by APC and thrombin, the APC-EPCR-PAR1 axis, and their potential roles in SCD.

Factor XII contributes to thrombotic complications and vaso-occlusion in sickle cell disease

A hypercoagulable state, chronic inflammation, and increased risk of venous thrombosis and stroke are prominent features in patients with sickle cell disease (SCD). Coagulation factor XII (FXII) triggers activation of the contact system that is known to be involved in both thrombosis and inflammation, but not in physiological hemostasis. Therefore, we investigated whether FXII contributes to the prothrombotic and inflammatory complications associated with SCD. We found that when compared with healthy controls, patients with SCD exhibit increased circulating biomarkers of FXII activation that are associated with increased activation of the contact pathway. We also found that FXII, but not tissue factor, contributes to enhanced thrombin generation and systemic inflammation observed in sickle cell mice challenged with tumor necrosis factor α. In addition, FXII inhibition significantly reduced experimental venous thrombosis, congestion, and microvascular stasis in a mouse model of SCD. Moreover, inhibition of FXII attenuated brain damage and reduced neutrophil adhesion to the brain vasculature of sickle cell mice after ischemia/reperfusion induced by transient middle cerebral artery occlusion. Finally, we found higher FXII, urokinase plasminogen activator receptor, and αMβ2 integrin expression in neutrophils of patients with SCD compared with healthy controls. Our data indicate that targeting FXII effectively reduces experimental thromboinflammation and vascular complications in a mouse model of SCD, suggesting that FXII inhibition may provide a safe approach for interference with inflammation, thrombotic complications, and vaso-occlusion in patients with SCD.

Radiation-induced H3K9 tri-methylation in E-cadherin promoter during lung EMT: in vitro and in vivo approaches using vanillin

Radiotherapy is an important treatment regime for lung cancer, worldwide. However, radiation-induced pneumonitis and fibrosis are the treatment-limiting toxicities among patients who have undergone radiotherapy. The epithelial cells via epithelial to mesenchymal transition [EMT] acquires mesenchymal phenotype, which ultimately leads to fibrosis. Many investigations are focussed on understanding the signalling pathways mediating in EMT, however, the role of histone methylation is less understood in radiation-induced lung EMT. In the present study, we analysed the effect of vanillin, an antioxidant, on histone methylation during radiation-induced EMT. The thoracic region of Wistar rats was irradiated with a fractionated dose of X-ray (3 Gy/day) for two weeks (total of 30 Gy). The irradiated animals were sacrificed at the 8th and 16th weeks and tissues were used for analyses. Our data showed that radiation decreased the level of antioxidant enzymes such as SOD, catalase and reduced glutathione that would ultimately enhance oxidative stress in the tissues. Histopathological analysis revealed that radiation increased the infiltration of inflammatory cells to the tissue injury site. Total global histone methylation was increased upon irradiation, which was effectively prevented by vanillin administration. Vanillin enhanced E-cadherin expression and decreased the mesenchymal markers N-cadherin and vimentin in the irradiated lung tissue. The ChIP-qPCR analysis suggested that snail expression in the nucleus might involve in the enrichment of suppressive marker H3K9me3 on the E-cadherin promoter. Finally, we suggested that vanillin administration decreased radiation-induced oxidative stress and EMT expression. Additionally, irradiation increased the H3K9 methylation status with nuclear translocation of snail during lung EMT.

Role of VEGF165b/VEGFTOTAL ratio in gestational diabetes mellitus

Proper vascular function is important for well-being of mother and growing fetus. VEGF_TOTAL, and VEGF_165b levels and its vascular endothelial complications in gestational diabetes mellitus (GDM) together with the association of inflammation and advanced glycation end products (AGEs) are less studied. VEGF_165b/VEGF_TOTAL (VEGF RATIO) in GDM pregnant women was investigated in this study. Plasma VEGF_TOTAL was lower in GDM (17.68 ± 1.30 pg/mL) compared to non-GDM (25.69 ± 1.40 pg/mL). VEGF_165b, ICAM-1, and AGEs were higher in GDM (9.9 ± 1.4 pg/mL, 201.04 ± 7.85 µg/mL, and 10.40 ± 0.98 µg/mL, respectively) and lower in non-GDM (6.47 ± 0.70 pg/mL, 174.1 ± 7.11 µg/mL, and 4.71 ± 0.39 µg/mL, respectively). Compared to non GDM (0.25 ± 0.02), VEGF RATIO was higher in GDM (0.45 ± 0.04) and correlated with -ICAM-1 (r = 0.375, p < .001) and AGEs (r = 0.199, p < .05). Tertile stratification of VEGF RATIO implied that frequency of GDM increases with increasing tertiles of VEGF RATIO (p for trend <.001). Association of VEGF RATIO with GDM was significant even after adjusting for AGEs (OR = 1.279, CI = 1.118-1.462, p < .0010) but it lost its significance when adjusted for ICAM-1 (OR = 1.006, CI = 0.995-1.017, p = .308). VEGF RATIO plays an important role in GDM in association with vascular inflammation.

Malnutrition in India: status and government initiatives

Malnutrition, according to the World Health Organization (WHO), refers to deficiencies, excesses, or imbalances in a person's intake of energy and/or nutrients. It is well-known that maternal, infant, and child nutrition play significant roles in the proper growth and development, including future socio-economic status of the child. Reports of National Health & Family Survey, United Nations International Children's Emergency Fund, and WHO have highlighted that rates of malnutrition among adolescent girls, pregnant and lactating women, and children are alarmingly high in India. Factors responsible for malnutrition in the country include mother's nutritional status, lactation behaviour, women's education, and sanitation. These affect children in several ways including stunting, childhood illness, and retarded growth. Although India has nominally reduced malnutrition over the last decade, and several government programs are in place, there remains a need for effective use of knowledge gained through studies to address undernutrition, especially because it impedes the socio-economic development of the country. These findings may provide useful lessons for other developing countries that are working towards reducing child malnutrition in their settings.

Early growth response-1 (EGR-1) - a key player in myocardial cell injury

Coronary heart disease is the leading cause of mortality worldwide, affecting millions of men and women every year. Elucidation of key signaling factors and their pathways are critical for understanding and developing novel therapeutic targets for protection of the myocardium from ischemia. EGR-1, an immediate early gene and a zinc finger transcription factor plays critical role in various cardiovascular patho-biological processes. This article reviews the growing evidence implicating EGR-1 pathway in myocardial ischemia/reperfusion, cardiac hypertrophy and other cardiovascular complications like atherosclerosis.

Molecular dynamics of human methemoglobin: the transmission of conformational information between subunits in an alpha beta dimer

Spectroscopic studies indicate an interaction of the distal histidine with the heme iron as well as the transmission of distal heme perturbations across the alpha1beta1 interface. Molecular dynamics simulations have been used to explain the molecular basis for these processes. Using a human methemoglobin alpha beta dimer, it has been shown that at 235 K after 61 ps, a rearrangement occurs in the alpha-chain corresponding to the formation of a bond with the distal histidine. This transition does not take place in the beta-chain during a 100-ps simulation and is reversed at 300 K. The absence of the distal histidine transition in the isolated chains and with the interface frozen indicate the involvement of the alphabeta interface. A detailed analysis of the simulation has been performed in terms of RMS fluctuations, domain cross-correlation maps, the disruption of helix hydrogen bonds, as well changes in electrostatic interactions and dihedral angles. This analysis shows that the rearrangements in the alpha-chain necessary to bring the histidine closer to the iron involve alterations primarily in the CD loop and at the interface. Communication to the beta-chain distal pocket is propagated by increased interactions of the alpha-chain B helix with the beta-chain G-GH-H segment and the flexibility in the EF loop. The G helices shown to be involved in propagation of perturbation across the alpha1beta1 interface extend into the alpha1beta2 interfaces, providing a mechansim whereby distal interactions can modulate the T<==>R transition in hemoglobin.