Immunometabolism and PI(3)K Signaling As a Link between IL-2, Foxp3 Expression, and Suppressor Function in Regulatory T Cells

CD4⁺ Foxp3⁺ regulatory T cells (Tregs) are an essential component of immune homeostasis. Modulation of Treg function has been proposed as a means of treating autoimmune conditions and preventing rejection of organ transplants, although achieving this goal will require a detailed understanding of Treg signaling pathways. Signaling within Tregs is known to differ considerably from that observed in other T cell subsets. Of note, Tregs are the only cell type known to constitutively express CD25, the main ligand-binding subunit of the IL-2 receptor. The PI(3)K/Akt/mTOR cascade constitutes a major signaling pathway downstream of IL-2 and is closely tied to cellular metabolism. Due to increasing recognition of the links between cellular fuel usage and immune cell function, the interplay between IL-2 signaling and Treg metabolism represents an important space for exploration and a potential approach for immunomodulation. Here, we discuss how IL-2 may affect Treg metabolism via PI(3)K signaling, as well as the effects of altered metabolism on Treg lineage stability and suppressor function.

Panax notoginseng saponins reduce high-risk factors for thrombosis through peroxisome proliferator-activated receptor -γ pathway

The classic Virchow theory suggests that blood stasis, hypercoagulability and endothelial dysfunction are three major factors that cause venous thrombosis (VT). It is a complicated biological process involved multi-factors. Platelet plays a central role and participates in multiple links of this process. Panax notoginseng saponins (PNS), the principal constituents derived from panax notoginseng, has been widely described for its anti-platelet activity. However, its potential mechanism against platelet aggregation has not been clarified. In this present study, we evaluated the anti-platelet effects of PNS on thrombin-induced platelet activation and its possible molecular mechanism of action, and further explored the therapeutic action of PNS on thrombin induced hypercoagulability in rat. Our results showed that PNS treatment inhibited platelet aggregation induced by thrombin, which was accompanied with over-expression of Peroxisome proliferator-activated receptor γ (PPAR-γ) protein, mRNA and upregulation of phosphatidylinositol 3 kinase (PI₃K)/ protein kinase B (Akt)/ endothelial nitric oxide synthase (eNOS) pathway in platelet, and this effect could be reversed by PPAR-γ inhibitor T0070907. In vivo, PNS significantly reversed thrombin-induced hypercoagulable state in rat which was accompanied by PPAR-γ protein and mRNA upregulation in rat lung. In conclusion, these data suggested that PNS could suppress thrombin-induced platelet aggregation in vitro and effectively improve hypercoagulable state in vivo and PNS-induced activation of PPAR-γ and its downstream PI₃K/Akt/eNOS pathway played the central role.

B-cell receptor signalling and its crosstalk with other pathways in normal and malignant cells

The physiology of B cells is intimately connected with the function of their B-cell receptor (BCR). B-cell lymphomas frequently (dys)regulate BCR signalling and thus take advantage of this pre-existing pathway for B-cell proliferation and survival. This has recently been underscored by clinical trials demonstrating that small molecules (fosfamatinib, ibrutinib, idelalisib) inhibiting BCR-associated kinases (SYK, BTK, PI3K) have an encouraging clinical effect. Here we describe the current knowledge of the specific aspects of BCR signalling in diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, chronic lymphocytic leukaemia (CLL) and normal B cells. Multiple factors can contribute to BCR pathway (dys)regulation in these malignancies and the activation of 'chronic' or 'tonic' BCR signalling. In lymphoma B cells, the balance of initiation, amplitude and duration of BCR activation can be influenced by a specific immunoglobulin structure, the expression and mutations of adaptor molecules (like GAB1, BLNK, GRB2, CARD11), the activity of kinases (like LYN, SYK, PI3K) or phosphatases (like SHIP-1, SHP-1 and PTEN) and levels of microRNAs. We also discuss the crosstalk of BCR with other signalling pathways (NF-κB, adhesion through integrins, migration and chemokine signalling) to emphasise that the 'BCR inhibitors' target multiple pathways interconnected with BCR, which might explain some of their clinical activity.

Estrogen, vascular estrogen receptor and hormone therapy in postmenopausal vascular disease

Cardiovascular disease (CVD) is less common in premenopausal women than men of the same age or postmenopausal women, suggesting vascular benefits of estrogen. Estrogen activates estrogen receptors ERα, ERβ and GPR30 in endothelium and vascular smooth muscle (VSM), which trigger downstream signaling pathways and lead to genomic and non-genomic vascular effects such as vasodilation, decreased VSM contraction and growth and reduced vascular remodeling. However, randomized clinical trials (RCTs), such as the Women's Health Initiative (WHI) and Heart and Estrogen/progestin Replacement Study (HERS), have shown little vascular benefits and even adverse events with menopausal hormone therapy (MHT), likely due to factors related to the MHT used, ER profile, and RCT design. Some MHT forms, dose, combinations or route of administration may have inadequate vascular effects. Age-related changes in ER amount, distribution, integrity and post-ER signaling could alter the vascular response to MHT. The subject's age, preexisting CVD, and hormone environment could also reduce the effects of MHT. Further evaluation of natural and synthetic estrogens, phytoestrogens, and selective estrogen-receptor modulators (SERMs), and the design of appropriate MHT combinations, dose, route and 'timing' could improve the effectiveness of conventional MHT and provide alternative therapies in the peri-menopausal period. Targeting ER using specific ER agonists, localized MHT delivery, and activation of specific post-ER signaling pathways could counter age-related changes in ER. Examination of the hormone environment and conditions associated with hormone imbalance such as polycystic ovary syndrome may reveal the causes of abnormal hormone-receptor interactions. Consideration of these factors in new RCTs such as the Kronos Early Estrogen Prevention Study (KEEPS) could enhance the vascular benefits of estrogen in postmenopausal CVD.

The impact of reactive oxygen species and genetic mitochondrial mutations in Parkinson's disease

The exact pathogenesis of Parkinson's disease (PD) is still unknown and proper mechanisms that correspond to the disease remain unidentified. It is understood that PD is age-related; as age increases, the chance of onset responds accordingly. Although there are no current means of curing PD, the understanding of reactive oxygen species (ROS) provides significant insight to possible treatments. Complex I deficiencies of the respiratory chain account for the majority of unfavorable neural apoptosis generation in PD. Dopaminergic neurons are severely damaged as a result of the deficiency. Symptoms such as inhibited cognitive ability and loss of smooth motor function are the results of such impairment. The genetic mutations of Parkinson's related proteins such as PINK1 and LRRK2 contribute to mitochondrial dysfunction which precedes ROS formation. Various pathways are inhibited by these mutations, and inevitably causing neural cell damage. Antioxidants are known to negate the damaging effects of free radical overexpression. This paper expands on the specific impact of mitochondrial genetic change and production of free radicals as well as its correlation to the neurodegeneration in Parkinson's disease.

Stressed out mitochondria: the role of mitochondria in ageing and cancer focussing on strategies and opportunities in human skin

Mitochondrial DNA damage has been used as a successful and unique biomarker of tissue stress. A valuable example of this is sun damage in human skin which leads to ageing and skin cancer. The skin is constantly exposed to the harmful effects of sunlight, such as ultraviolet radiation, which causes it to age with observable characteristic features as well as clinical precancerous lesions and skin cancer. Formation of free radicals by the sun's harmful rays which contribute to oxidative stress has been linked to the induction of deletions and mutations in the mitochondrial DNA. These markers of mitochondrial DNA damage have been proposed to contribute to the mechanisms of ageing in many tissues including skin and are associated with many diseases including cancer. In this article we highlight the role of this important organelle in ageing and cancer with particular emphasis on experimental strategies in the skin.