Glucose and glucose transporters regulate lymphatic pump activity through activation of the mitochondrial ATP-sensitive K+ channel

Direct Targets and Subsequent Pathways for Molecular Hydrogen to Exert Multiple Functions: Focusing on Interventions in Radical Reactions

Molecular hydrogen (H₂) was long regarded as non-functional in mammalian cells. We overturned the concept by demonstrating that H₂ exhibits antioxidant effects and protects cells against oxidative stress. Subsequently, it has been revealed that H₂ has multiple functions in addition to antioxidant effects, including antiinflammatory, anti-allergic functions, and as cell death and autophagy regulation. Additionally, H₂ stimulates energy metabolism. As H₂ does not readily react with most biomolecules without a catalyst, it is essential to identify the primary targets with which H₂ reacts or interacts directly. As a first event, H₂ may react directly with strong oxidants, such as hydroxyl radicals (•OH) in vivo. This review addresses the key issues related to this in vivo reaction. •OH may have a physiological role because it triggers a free radical chain reaction and may be involved in the regulation of Ca2+- or mitochondrial ATP-dependent K+-channeling. In the subsequent pathway, H₂ suppressed a free radical chain reaction, leading to decreases in lipid peroxide and its end products. Derived from the peroxides, 4-hydroxy-2-nonenal functions as a mediator that up-regulates multiple functional PGC-1α. As the other direct target in vitro and in vivo, H₂ intervenes in the free radical chain reaction to modify oxidized phospholipids, which may act as an antagonist of Ca2+-channels. The resulting suppression of Ca2+-signaling inactivates multiple functional NFAT and CREB transcription factors, which may explain H₂ multi-functionality. This review also addresses the involvement of NFAT in the beneficial role of H₂ in COVID-19, Alzheimer's disease and advanced cancer. We discuss some unsolved issues of H₂ action on lipopolysaccharide signaling, MAPK and NF-κB pathways and the Nrf2 paradox. Finally, as a novel idea for the direct targeting of H2, this review introduces the possibility that H₂ causes structural changes in proteins via hydrate water changes.

Direct cardiovascular impact of SGLT2 inhibitors: mechanisms and effects

Diabetes is a global epidemic and a leading cause of death with more than 422 million patients worldwide out of whom around 392 million alone suffer from type 2 diabetes (T2D). Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are novel and effective drugs in managing glycemia of T2D patients. These inhibitors gained recent clinical and basic research attention due to their clinically observed cardiovascular protective effects. Although interest in the study of various SGLT isoforms and the effect of their inhibition on cardiovascular function extends over the past 20 years, an explanation of the effects observed clinically based on available experimental data is not forthcoming. The remarkable reduction in cardiovascular (CV) mortality (38%), major CV events (14%), hospitalization for heart failure (35%), and death from any cause (32%) observed over a period of 2.6 years in patients with T2D and high CV risk in the EMPA-REG OUTCOME trial involving the SGLT2 inhibitor empagliflozin (Empa) have raised the possibility that potential novel, more specific mechanisms of SGLT2 inhibition synergize with the known modest systemic improvements, such as glycemic, body weight, diuresis, and blood pressure control. Multiple studies investigated the direct impact of SGLT2i on the cardiovascular system with limited findings and the pathophysiological role of SGLTs in the heart. The direct impact of SGLT2i on cardiac homeostasis remains controversial, especially that SGLT1 isoform is the only form expressed in the capillaries and myocardium of human and rodent hearts. The direct impact of SGLT2i on the cardiovascular system along with potential lines of future research is summarized in this review.

Method for the quantitative measurement of collecting lymphatic vessel contraction in mice

Collecting lymphatic vessels are critical for the transport of lymph and its cellular contents to lymph nodes for both immune surveillance and the maintenance of tissue-fluid balance. Collecting lymphatic vessels drive lymph flow by autonomous contraction of smooth muscle cells that cover these vessels. Here we describe methods using intravital microscopy to image and quantify collecting lymphatic vessel contraction in mice. Our methods allow for the measurement of the strength of lymphatic contraction of an individual lymphangion in a mouse, which has not yet been demonstrated using other published methods. The ability to study murine collecting lymphatic vessel contraction-using the methods described here or other recently published techniques-allows the field to dissect the molecular mechanisms controlling lymphatic pumping under normal and pathological conditions using the wide variety of molecular tools and genetic models available in the mouse. We have used our methods to study lymphatic contraction in physiological and inflammatory conditions. The methods described here will facilitate the further study of lymphatic function in other pathological conditions that feature lymphatic complications.

Lymphatic vessels in health and disease

The lymphatic vasculature plays vital roles in tissue fluid balance, immune defense, metabolism, and cancer metastasis. In adults, lymphatic vessel formation and remodeling occur primarily during inflammation, development of the corpus luteum, wound healing, and tumor growth. Unlike the blood circulation, where unidirectional flow is sustained by the pumping actions of the heart, pumping actions intrinsic to the lymphatic vessels themselves are important drivers of lymphatic flow. This review summarizes critical components that control lymphatic physiology.

Impaired lymphatic contraction associated with immunosuppression

To trigger an effective immune response, antigen and antigen-presenting cells travel to the lymph nodes via collecting lymphatic vessels. However, our understanding of the regulation of collecting lymphatic vessel function and lymph transport is limited. To dissect the molecular control of lymphatic function, we developed a unique mouse model that allows intravital imaging of autonomous lymphatic vessel contraction. Using this method, we demonstrated that endothelial nitric oxide synthase (eNOS) in lymphatic endothelial cells is required for robust lymphatic contractions under physiological conditions. By contrast, under inflammatory conditions, inducible NOS (iNOS)-expressing CD11b(+)Gr-1(+) cells attenuate lymphatic contraction. This inhibition of lymphatic contraction was associated with a reduction in the response to antigen in a model of immune-induced multiple sclerosis. These results suggest the suppression of lymphatic function by the CD11b(+)Gr-1(+) cells as a potential mechanism of self-protection from autoreactive responses during on-going inflammation. The central role for nitric oxide also suggests that other diseases such as cancer and infection may also mediate lymphatic contraction and thus immune response. Our unique method allows the study of lymphatic function and its molecular regulation during inflammation, lymphedema, and lymphatic metastasis.

Nimesulide aggravates redox imbalance and calcium dependent mitochondrial permeability transition leading to dysfunction in vitro

Nimesulide (selective cyclooxygenase-2 inhibitor) is a nonsteroidal anti-inflammatory drug for the symptomatic treatment of painful conditions like osteoarthritis, spondilitis and primary dysmenorrhoea. Nimesulide induced liver damage is a serious side effect of this otherwise popular drug. The mechanism involved in nimesulide induced hepatotoxicity is still not fully elucidated. However, both mitochondrial dysfunction and oxidative stress have been implicated in contributing to liver injury in susceptible patients. Mitochondria besides being the primary source of energy, act as a hub of signals responsible for initiating cell death, irrespective of the pathway, i.e. apoptosis or necrosis. The present study was aimed to explore the role of compounding stress, i.e. Ca(2+) overload and GSH depletion in nimesulide induced mitochondrial toxicity and dysfunction. Our study showed that, nimesulide (100 microM) treatment resulted into rapid depletion of GSH (60%) in isolated rat liver mitochondria and significant Ca(2+) dependent MPT changed. Enhanced ROS generation (DCF fluorescence) was also observed in mitochondria treated with nimesulide. An important finding was that the concentration at which nimesulide oxidized reduced pyridine nucleotides (autofluorescence of NAD(P)H), it affected mitochondrial electron flow (MTT activity decreased by 75%) and enhanced mitochondrial depolarization significantly as assessed by Rhodamine 123 fluorescent probe. Therefore, nimesulide was found to aggravate redox imbalance and affect Ca(2+) dependent mitochondrial membrane permeability transition leading to dysfunction and ultimately cell death.