Keeping Up with Sea-Level Rise: Salt Marsh Accretion. Subjects: Earth Science, Marine / Ocean Science Grades: 9-12

This lesson uses a hands-on demonstration to give students an understanding of how this critical ecosystem can keep pace with sea-level rise. Students will have the opportunity to make and test hypotheses about how different animals can affect salt marsh resilience, after learning about simple ecological interactions

Sea Level Rise may Increase Extinction Risk of a Saltmarsh Ontogenetic Habitat Specialist

Specialist species are more vulnerable to environmental change than generalist species. For species with ontogenetic niche shifts, specialization may occur at a particular life stage making those stages more susceptible to environmental change. In the salt marshes in the northeast U.S., accelerated sea level rise is shifting vegetation patterns from flood-intolerant species such as Spartina patens to the flood-tolerant Spartina alterniflora. We tested the potential impact of this change on the coffee bean snail, Melampus bidentatus, a numerically dominant benthic invertebrate with an ontogenetic niche shift. From a survey of eight marshes throughout the northeast U.S., small snails were found primarily in S. patens habitats, and large snails were found primarily in stunted S. alterniflora habitats. When transplanted into stunted S. alterniflora, small snails suffered significantly higher mortality relative to those in S. patens habitats; adult snail survivorship was similar between habitats. Because other habitats were not interchangeable with S. patens for young snails, these results suggest that Melampus is an ontogenetic specialist where young snails are habitat specialists and adult snails are habitat generalists. Temperature was significantly higher and relative humidity significantly lower in stunted S. alterniflorathan in S. patens. These data suggest that thermal and desiccation stress restricted young snails to S. patens habitat, which has high stem density and a layer of thatch that protects snails from environmental stress. Other authors predict that if salt marshes in the northeast U.S. are unable to migrate landward, sea level rise will eliminate S. patenshabitats. We suggest that if a salt marsh loses its S. patens habitats, it will also lose its coffee bean snails. Our results demonstrate the need to consider individual life stages when determining a species’ vulnerability to global change

Connexin-43 hemichannel mediated ATP release stimulates fibroblast activation in an in vitro model of diabetic kidney disease

Aims: Tubulointerstitial fibrosis is the underlying pathology of diabetic nephropathy and develops in response to aberrant activation of multiple cell types within and around the proximal tubule of the kidney, including extracellular matrix (ECM) producing fibroblasts. Whilst we previously reported a role for connexin-43 (Cx43) hemichannel activity in tubule inflammation, the function and extent to which fibroblast hemichannels contribute to this damage, remains to be determined. Methods: Human kidney fibroblasts (TK173) were cultured in the glucose-evoked cytokine transforming growth factor-beta1 (TGFb1) ± Cx43 hemichannel blocker Tonabersat, for 48hrs. Immunoblotting determined protein expression, whilst carboxyfluorescein dye uptake and an ATP lite assay assessed hemichannel-mediated ATP release. Results: TGFb1 significantly increased hemichannel-mediated dye uptake by 73.6±3.9%, (P < 0.001, n = 4) in TK173 cells compared to control, an effect reduced when co-incubated with Tonabersat (P < 0.01, n = 4). The profibrotic cytokine TGFb1 increased ATP release by 92.8±13.9%, with Tonabersat decreasing ATP release by 90.8±25.8% (P < 0.05, n = 4). Immunoblotting deter- mined that TGFb1 increased expression of the ECM pro-teins, fibronectin (330.8±16.4%, P < 0.001, n = 5) and collagen I (42.9±4.6%, P < 0.001, n = 5), and the prin-cipal Wnt signalling mediator b-catenin (91.8±6.6%, P < 0.001, n = 5) compared to control. Tonabersat restored expression of fibronectin, collagen I and b-catenin by 98±29.6%, (P < 0.01, n = 5), 20±6.8%, (P < 0.05, n = 5), and 56.9±26.7%, (P < 0.05, n = 5) respectively. Conclusion: These data suggest that glucose-evoked changes in TGFb1, increase hemichannel-mediated ATP release and downstream expression of fibrotic candidates in human renal fibroblasts. The study indicates that Cx43 hemichannels may represent a future therapeutic target for alleviating tubulointerstitial fibrosis in people with diabetic kidney disease

Blocking connexin 43 hemichannel-mediated ATP release reduces communication within and between tubular epithelial cells and medullary fibroblasts in a model of diabetic nephropathy

Introduction: Fibrosis of renal tubules is the final common pathway in diabetic nephropathy and develops in the face of tubular injury and fibroblast activation. Aberrant connexin 43 (Cx43) hemichannel activity has been linked to this damage under euglycaemic conditions, however, its role in glycaemic injury is unknown. This study investigated the effect of a Cx43 blocker (Tonabersat) on hemichannel activity and cell–cell interactions within and between tubular epithelial cells and fibroblasts in an in vitro model of diabetic nephropathy. Methods: Human kidney (HK2) proximal tubule epithelial cells and medul- lary fibroblasts (TK173) were treated in low (5mM) or high (25mM) glucose ± transforming growth factor beta-1 (TGFβ1)±Tonabersat in high glucose. Carboxyfluorescein dye uptake and ATPlite luminescence assessed changes in hemichannel-mediated ATP release, while immunoblotting determined protein expression. Co-incubation with the ATP-diphosphohydrolase apyrase or a P2X7R inhibitor (A438079) assessed ATP-P2X7R signalling. Indirect co-culture with conditioned media from the alternate cell type evaluated paracrine-mediated het- erotypic interactions. Results: Tonabersat partially negated glucose/TGFβ1-induced increases in Cx43 hemichannel-mediated ATP release and downstream changes in adherens junc- tion and extracellular matrix (ECM) protein expression in HK2 and TK173 cells. Apyrase and A438079 highlighted the role for ATP-P2X7R in driving changes in protein expression in TK173 fibroblasts. Indirect co-culture studies suggest that epithelial cell secretome increases Tonabersat-sensitive hemichannel-mediated dye uptake in fibroblasts and downstream protein expression. Conclusion: Tonabersat-sensitive hemichannel-mediated ATP release en- hances TGFβ1-driven heterotypic cell–cell interaction and favours myofibroblast activation. The data supports the potential benefit of Cx43 inhibition in reducing tubulointerstitial fibrosis in late-stage diabetic nephropathy

The Role of the NLRP3 Inflammasome in Mediating Glomerular and Tubular Injury in Diabetic Nephropathy

The NOD-like receptor protein 3 (NLRP3) inflammasome is a multi-protein signalling complex integral to the chronic inflammatory response, activated in response to sterile and non-sterile cellular damage. The assembly and activation of the NLRP3 inflammasome comprise a two-step process involving nuclear factor kappa B (NFkB)-mediated priming, followed by canonical, non-canonical or alternative signalling pathways. These result in the maturation and release of inflammatory cytokines interleukin 1 beta (IL1ß) and interleukin- 18 (IL18), which are associated with chronic inflammatory conditions including diabetic kidney disease. Diabetic nephropathy is a condition affecting ~40% of people with diabetes, the key underlying pathology of which is tubulointerstitial inflammation and fibrosis. There is growing evidence to suggest the involvement of the NLRP3 inflammasome in this chronic inflammation. Early deterioration of kidney function begins in the glomerulus, with tubular inflammation dictating the progression of late- stage disease. Priming and activation of the NLRP3 inflammasome have been linked to several clinical markers of nephropathy including proteinuria and albuminuria, in addition to morphological changes including mesangial expansion. Treatment options for diabetic nephropathy are limited, and research that examines the impact of directly targeting the NLRP3 inflammasome, or associated downstream components are beginning to gain favour, with several agents currently in clinical trials. This review will explore a role for NLRP3 inflammasome activation and signalling in mediating inflammation in diabetic nephropathy, specifically in the glomerulus and proximal tubule, before briefly describing the current position of therapeutic research in this field

Connexin mediated cell communication in the kidney, a potential therapeutic target for future intervention of diabetic kidney disease?

The ability of cells to communicate and synchronise their activity is essential for the maintenance of tissue structure, integrity and function. A family of membrane-bound proteins called connexins are largely responsible for mediating the local transfer of information between cells. Assembled in the cell membrane as a hexameric connexon, they function either as a conduit for paracrine signalling, forming a trans-membrane hemi-channel or, if aligned with connexons on neighbouring cells, form a continuous aqueous pore, or gap junction, which allows for the direct transmission of metabolic and electrical signals. Regulation of connexin synthesis and activity is critical to cellular function and a number of diseases are attributed to changes in the expression and/or function of these important proteins. A link between hyperglycaemia, connexin expression, altered nucleotide concentrations and impaired function, highlights a potential role for connexin-mediated cell communication in complications of diabetes. In the diabetic kidney, glycaemic injury is the leading cause of end stage renal failure, reflecting multiple aetiologies including glomerular hyperfiltration, albuminuria, increased deposition of extracellular matrix, and tubulointerstitial fibrosis. Loss of connexin-mediated cell-to-cell communication in diabetic nephropathy may represent an early sign of disease progression, however, our understanding of the process remains severely limited. This review focusses on recent evidence demonstrating that glucose-evoked changes in connexin mediated cell communication and associated purinergic signalling, may contribute to the pathogenesis of kidney disease in diabetes, highlighting the tantalising potential of targeting these proteins as a novel therapeutic intervention

Are coastal habitats important nurseries? A meta-analysis

Nearshore‐structured habitats—including underwater grasses, mangroves, coral, and other biogenic reefs, marshes, and complex abiotic substrates—have long been postulated to function as important nurseries for juvenile fishes and invertebrates. Here, we review the evolution of the “nursery habitat hypothesis” and use \u3e11,000 comparisons from 160 peer‐reviewed studies to test whether and which structured habitats increase juvenile density, growth, and survival. In general, almost all structured habitats significantly enhanced juvenile density—and in some cases growth and survival—relative to unstructured habitats. Underwater grasses and mangroves also promoted juvenile density and growth beyond what was observed in other structured habitats. These conclusions were robust to variation among studies, although there were significant differences with latitude and among some phyla. Our results confirm the basic nursery function of certain structured habitats, which lends further support to their conservation, restoration, and management at a time when our coastal environments are becoming increasingly impacted. They also reveal a dearth of evidence from many other systems (e.g., kelp forests) and for responses other than density. Although recent studies have advocated for increasingly complex approaches to evaluating nurseries, we recommend a renewed emphasis on more straightforward assessments of juvenile growth, survival, reproduction, and recruitment

Limiting Pseudomonas aeruginosa Biofilm Formation Using Cold Atmospheric Pressure Plasma

We investigate the ability to disrupt and limit growth biofilms of Pseudomonas aeruginosa using application of cold atmospheric pressure (CAP) plasma. The effect of the bio-film's exposure to a helium (CAP) jet was assessed at varying time points during biofilm maturation. Results showed that the amount of time during biofilm growth that CAP pressure was applied has a crucial role on the ability of biofilms to mature and recover after CAP exposure. Intervention during the early stages of biofilm formation (0-8 h) results in a 4-5-log reduction in viable bacterial cells (measured at 24 h of incubation) relative to untreated biofilms. However, CAP treatment of biofilm at 12 h and above only results in a 2-log reduction in viable cells. This has potentially important implications for future clinical application of CAP to treat infected wounds

Connexin 43: A target for the treatment of inflammation in secondary complications of the kidney and eye in diabetes

Of increasing prevalence, diabetes is characterised by elevated blood glucose and chronic inflammation that precedes the onset of multiple secondary complications, including those of the kidney and the eye. As the leading cause of end stage renal disease and blindness in the working population, more than ever is there a demand to develop clinical interventions which can both delay and prevent disease progression. Connexins are membrane bound proteins that can form pores (hemichannels) in the cell membrane. Gated by cellular stress and injury, they open under patho- physiological conditions and in doing so release ‘danger signals’ including adenosine triphosphate into the extracellular environment. Linked to sterile inflammation via activation of the nod-like receptor protein 3 inflammasome, targeting aberrant hemichannel activity and the release of these danger signals has met with favourable outcomes in multiple models of disease, including secondary complications of diabetes. In this review, we provide a comprehensive update on those studies which document a role for aberrant connexin hemichannel activity in the pathogenesis of both diabetic eye and kidney disease, ahead of evaluating the efficacy of blocking connexin-43 specific hemichannels in these target tissues on tissue health and function