Sirtuin1 Over-Expression Does Not Impact Retinal Vascular and Neuronal Degeneration in a Mouse Model of Oxygen-Induced Retinopathy

Proliferative retinopathy is a leading cause of blindness, including retinopathy of prematurity (ROP) in children and diabetic retinopathy in adults. Retinopathy is characterized by an initial phase of vessel loss, leading to tissue ischemia and hypoxia, followed by sight threatening pathologic neovascularization in the second phase. Previously we found that Sirtuin1 (Sirt1), a metabolically dependent protein deacetylase, regulates vascular regeneration in a mouse model of oxygen-induced proliferative retinopathy (OIR), as neuronal depletion of Sirt1 in retina worsens retinopathy. In this study we assessed whether over-expression of Sirtuin1 in retinal neurons and vessels achieved by crossing Sirt1 over-expressing flox mice with Nestin-Cre mice or Tie2-Cre mice, respectively, may protect against retinopathy. We found that over-expression of Sirt1 in Nestin expressing retinal neurons does not impact vaso-obliteration or pathologic neovascularization in OIR, nor does it influence neuronal degeneration in OIR. Similarly, increased expression of Sirt1 in Tie2 expressing vascular endothelial cells and monocytes/macrophages does not protect retinal vessels in OIR. In addition to the genetic approaches, dietary supplement with Sirt1 activators, resveratrol or SRT1720, were fed to wild type mice with OIR. Neither treatment showed significant vaso-protective effects in retinopathy. Together these results indicate that although endogenous Sirt1 is important as a stress-induced protector in retinopathy, over-expression of Sirt1 or treatment with small molecule activators at the examined doses do not provide additional protection against retinopathy in mice. Further studies are needed to examine in depth whether increasing levels of Sirt1 may serve as a potential therapeutic approach to treat or prevent retinopathy

Neuronal sirtuin1 mediates retinal vascular regeneration in oxygen-induced ischemic retinopathy

Regeneration of blood vessels in ischemic neuronal tissue is critical to reduce tissue damage in diseases. In proliferative retinopathy, initial vessel loss leads to retinal ischemia, which can induce either regrowth of vessels to restore normal metabolism and minimize damage, or progress to hypoxia-induced sight-threatening pathologic vaso-proliferation. It is not well understood how retinal neurons mediate regeneration of vascular growth in response to ischemic insults. In this study we aim to investigate the potential role of Sirtuin 1 (Sirt1), a metabolically-regulated protein deacetylase, in mediating the response of ischemic neurons to regulate vascular regrowth in a mouse model of oxygen-induced ischemic retinopathy (OIR). We found that Sirt1 is highly induced in the avascular ischemic retina in OIR. Conditional depletion of neuronal Sirt1 leads to significantly decreased retinal vascular regeneration into the avascular zone and increased hypoxia-induced pathologic vascular growth. This effect is likely independent of PGC-1α, a known Sirt1 target, as absence of PGC-1α in knockout mice does not impact vascular growth in retinopathy. We found that neuronal Sirt1 controls vascular regrowth in part through modulating deacetylation and stability of hypoxia-induced factor 1α and 2α, and thereby modulating expression of angiogenic factors. These results indicate that ischemic neurons induce Sirt1 to promote revascularization into ischemic neuronal areas, suggesting a novel role of neuronal Sirt1 in mediating vascular regeneration in ischemic conditions, with potential implications beyond retinopathy

Insight the C-Site Pocket Conformational Changes Responsible for Sirtuin 2 Activity Using Molecular Dynamics Simulations

Sirtuin belongs to a family of typical histone deacetylase which regulates the fundamental cellular biological processes including gene expression, genome stability, mitosis, nutrient metabolism, aging, mitochondrial function, and cell motility. Michael et. al. reported that B-site mutation (Q167A and H187A) decreased the SIRT2 activity but still the structural changes were not reported. Hence, we performed 5 ns molecular dynamics (MD) simulation on SIRT2 Apo-form and complexes with substrate/NAD+ and inhibitor of wild type (WT), Q167A, and H187A. The results revealed that the assembly and disassembly of C-site induced by presence of substrate/NAD+ and inhibitor, respectively. This assembly and disassembly was mainly due to the interaction between the substrate/NAD+ and inhibitor and F96 and the distance between F96 and H187 which are present at the neck of the C-site. MD simulations suggest that the conformational change of L3 plays a major role in assembly and disassembly of C-site. Our current results strongly suggest that the distinct conformational change of L3 as well as the assembly and disassembly of C-site plays an important role in SIRT2 deacetylation function. Our study unveiled the structural changes of SIRT2 in presence of NAD+ and inhibitor which should be helpful to improve the inhibitory potency of SIRT2

A concept for international societally relevant microbiology education and microbiology knowledge promulgation in society

Microbes are all pervasive in their distribution and influence on the functioning and well-being of humans, life in general and the planet. Microbially-based technologies contribute hugely to the supply of important goods and services we depend upon, such as the provision of food, medicines and clean water. They also offer mechanisms and strategies to mitigate and solve a wide range of problems and crises facing humanity at all levels, including those encapsulated in the sustainable development goals (SDGs) formulated by the United Nations. For example, microbial technologies can contribute in multiple ways to decarbonisation and hence confronting global warming, provide sanitation and clean water to the billions of people lacking them, improve soil fertility and hence food production and develop vaccines and other medicines to reduce and in some cases eliminate deadly infections. They are the foundation of biotechnology, an increasingly important and growing business sector and source of employment, and the centre of the bioeconomy, Green Deal, etc. But, because microbes are largely invisible, they are not familiar to most people, so opportunities they offer to effectively prevent and solve problems are often missed by decision-makers, with the negative consequences this entrains. To correct this lack of vital knowledge, the International Microbiology Literacy Initiative–the IMiLI–is recruiting from the global microbiology community and making freely available, teaching resources for a curriculum in societally relevant microbiology that can be used at all levels of learning. Its goal is the development of a society that is literate in relevant microbiology and, as a consequence, able to take full advantage of the potential of microbes and minimise the consequences of their negative activities. In addition to teaching about microbes, almost every lesson discusses the influence they have on sustainability and the SDGs and their ability to solve pressing problems of societal inequalities. The curriculum thus teaches about sustainability, societal needs and global citizenship. The lessons also reveal the impacts microbes and their activities have on our daily lives at the personal, family, community, national and global levels and their relevance for decisions at all levels. And, because effective, evidence-based decisions require not only relevant information but also critical and systems thinking, the resources also teach about these key generic aspects of deliberation. The IMiLI teaching resources are learner-centric, not academic microbiology-centric and deal with the microbiology of everyday issues. These span topics as diverse as owning and caring for a companion animal, the vast range of everyday foods that are produced via microbial processes, impressive geological formations created by microbes, childhood illnesses and how they are managed and how to reduce waste and pollution. They also leverage the exceptional excitement of exploration and discovery that typifies much progress in microbiology to capture the interest, inspire and motivate educators and learners alike. The IMiLI is establishing Regional Centres to translate the teaching resources into regional languages and adapt them to regional cultures, and to promote their use and assist educators employing them. Two of these are now operational. The Regional Centres constitute the interface between resource creators and educators–learners. As such, they will collect and analyse feedback from the end-users and transmit this to the resource creators so that teaching materials can be improved and refined, and new resources added in response to demand: educators and learners will thereby be directly involved in evolution of the teaching resources. The interactions between educators–learners and resource creators mediated by the Regional Centres will establish dynamic and synergistic relationships–a global societally relevant microbiology education ecosystem–in which creators also become learners, teaching resources are optimised and all players/stakeholders are empowered and their motivation increased. The IMiLI concept thus embraces the principle of teaching societally relevant microbiology embedded in the wider context of societal, biosphere and planetary needs, inequalities, the range of crises that confront us and the need for improved decisioning, which should ultimately lead to better citizenship and a humanity that is more sustainable and resilient. The biosphere of planet Earth is a microbial world: a vast reactor of countless microbially driven chemical transformations and energy transfers that push and pull many planetary geochemical processes, including the cycling of the elements of life, mitigate or amplify climate change (e.g., Nature Reviews Microbiology, 2019, 17, 569) and impact the well-being and activities of all organisms, including humans. Microbes are both our ancestors and creators of the planetary chemistry that allowed us to evolve (e.g., Life's engines: How microbes made earth habitable, 2023). To understand how the biosphere functions, how humans can influence its development and live more sustainably with the other organisms sharing it, we need to understand the microbes. In a recent editorial (Environmental Microbiology, 2019, 21, 1513), we advocated for improved microbiology literacy in society. Our concept of microbiology literacy is not based on knowledge of the academic subject of microbiology, with its multitude of component topics, plus the growing number of additional topics from other disciplines that become vitally important elements of current microbiology. Rather it is focused on microbial activities that impact us–individuals/communities/nations/the human world–and the biosphere and that are key to reaching informed decisions on a multitude of issues that regularly confront us, ranging from personal issues to crises of global importance. In other words, it is knowledge and understanding essential for adulthood and the transition to it, knowledge and understanding that must be acquired early in life in school. The 2019 Editorial marked the launch of the International Microbiology Literacy Initiative, the IMiLI. HERE, WE PRESENT our concept of how microbiology literacy may be achieved and the rationale underpinning it; the type of teaching resources being created to realise the concept and the framing of microbial activities treated in these resources in the context of sustainability, societal needs and responsibilities and decision-making; and the key role of Regional Centres that will translate the teaching resources into local languages, adapt them according to local cultural needs, interface with regional educators and develop and serve as hubs of microbiology literacy education networks. The topics featuring in teaching resources are learner-centric and have been selected for their inherent relevance, interest and ability to excite and engage. Importantly, the resources coherently integrate and emphasise the overarching issues of sustainability, stewardship and critical thinking and the pervasive interdependencies of processes. More broadly, the concept emphasises how the multifarious applications of microbial activities can be leveraged to promote human/animal, plant, environmental and planetary health, improve social equity, alleviate humanitarian deficits and causes of conflicts among peoples and increase understanding between peoples (Microbial Biotechnology, 2023, 16(6), 1091–1111). Importantly, although the primary target of the freely available (CC BY-NC 4.0) IMiLI teaching resources is schoolchildren and their educators, they and the teaching philosophy are intended for all ages, abilities and cultural spectra of learners worldwide: in university education, lifelong learning, curiosity-driven, web-based knowledge acquisition and public outreach. The IMiLI teaching resources aim to promote development of a global microbiology education ecosystem that democratises microbiology knowledge.http://www.wileyonlinelibrary.com/journal/mbt2hj2024BiochemistryGeneticsMicrobiology and Plant PathologySDG-01:No povertySDG-02:Zero HungerSDG-03:Good heatlh and well-beingSDG-04:Quality EducationSDG-06:Clean water and sanitationSDG-07:Affordable and clean energySDG-08:Decent work and economic growthSDG-12:Responsible consumption and productionSDG-13:Climate actionSDG-14:Life below wate

Resveratrol treatment does not suppress vascular pathologies in OIR.

<p>C57Bl/6 mouse pups were exposed to 75% oxygen from P7 to P12 to induce retinopathy. Littermate mouse pups were treated with resveratrol or vehicle control through daily oral gavage from P5 to P17. Retinas were dissected at P17 and stained with Isolectin B₄ to visualize vessels. a) Representative images of retina flat-mounts from resveratrol treated mice and littermate vehicle controls at P17 after OIR. Areas of retinal vaso-obliteration(VO) in OIR and pathologic neovascularization(NV) were highlighted in white. Scale bar: 1000 µm. b) Quantification of vaso-obliteration as percent of total retinal areas in resveratrol treated mice compared to littermate controls. c) Quantification of pathologic NV in OIR as percent of total retinal areas in resveratrol treated mice compared to littermate controls. n = 15–18/group; *p<0.05; n.s.: not significant.</p

Sirt1 over-expression in retinal neurons does not protect against vascular degeneration in oxygen-induced retinopathy (OIR).

<p>a) Schematic illustration of OIR and representative images of retinal flat-mount with OIR and normoxic control retina at P17. To induce retinopathy, mice were exposed to 75% oxygen from P7 to P12. Retinas were dissected at P17 and stained with Isolectin B₄ (red) to visualize vessels. Lower panels show enlarged areas of normal vessels in control retina and abnormal pathologic neovascularization in OIR retina. Scale bars: top panels: 1000 µm. Bottom panels: 150 µm. b) Increased Sirt1 levels in <i>Nes-Sirt1^OE</i> retinas compared to control retinas, both in normal room air and with induced OIR. c) Representative images of retinal vasculature from <i>Nes-Sirt1^OE</i> and littermate controls with induced OIR at P17. Areas of vaso-obliteration(VO) or pathologic neovascularization (NV) were highlighted in white. d) Quantification of retinal vaso-obliteration in OIR as percent of total retinal areas in <i>Nes-Sirt1^OE</i> retinas and littermate controls. e) Quantification of pathologic neovascularization in OIR as percent of total retinal areas in <i>Nes-Sirt1^OE</i> retinas and littermate controls. n = 15–20/group. ***p<0.001; n.s.: not significant.</p

Sirt1 activator SRT1720 does not suppress vascular pathologies in OIR.

<p>C57Bl/6 mouse pups were exposed to 75% oxygen from P7 to P12 to induce retinopathy. Littermate mouse pups were treated with SRT1720 or vehicle controls through daily oral gavage from P5 to P17. Retinas were dissected at P17 and stained with Isolectin B₄ to visualize vessels. a) Representative images of retina flat-mounts from SRT1720 treated mice and littermate vehicle controls at P17 after OIR. Areas of vaso-obliteration(VO) or pathologic neovascularization(NV) were highlighted in white. Scale bar: 1000 µm. b) Quantification of retinal vaso-obliteration in OIR as percent of total retinal areas in SRT1720 treated mice compared to littermate controls. c) Quantification of pathologic NV in OIR as percent of total retinal areas in SRT1720 treated mice compared to littermate controls. n = 18–20/group; *p<0.05; n.s.: not significant.</p

Neuronal overexpression of Sirt1 does not protect against neuronal degeneration in OIR.

<p>a) Representative images of retinal cross sections from OIR retinas and age-matched normoxic control retinas at P17. Paraffin embedded retinal cross sections were stained with H&E to visualize cellular structures. b) Total retinal thickness was quantified from OIR retinas and compared to normoxic control retinas. n = 6/group. c) Representative images of retina cross sections from <i>Nes-Sirt1^OE</i> mouse and littermate flox control mice at P17 after OIR. <i>Nes-Sirt1^OE</i> and littermate control mice were exposed to 75% oxygen from P7 to P12 to induce retinopathy. Retinas were dissected at P17 and paraffin embedded sections were stained with H&E to visualize cellular structure. d) Quantification of total retinal thickness from OIR exposed <i>Nes-Sirt1^OE</i> mice and littermate flox control mice. n = 6/group. ***p<0.001; n.s.: not significant. Scale bars: 100 µm.</p