Isotopic evidence of environmental changes during the Devonian-Carboniferous transition in South China and its implications for the biotic crisis.

The Devonian-Carboniferous (D-C) transition coincides with the Hangenberg Crisis, carbon isotope anomalies, and the enhanced preservation of organic matter associated with marine redox fluctuations. The proposed driving factors for the biotic extinction include variations in the eustatic sea level, paleoclimate fluctuation, climatic conditions, redox conditions, and the configuration of ocean basins. To investigate this phenomenon and obtain information on the paleo-ocean environment of different depositional facies, we studied a shallow-water carbonate section developed in the periplatform slope facies on the southern margin of South China, which includes a well-preserved succession spanning the D-C boundary. The integrated chemostratigraphic trends reveal distinct excursions in the isotopic compositions of bulk nitrogen, carbonate carbon, organic carbon, and total sulfur. A distinct negative δ15 N excursion (~-3.1‰) is recorded throughout the Middle Si. praesulcata Zone and the Upper Si. praesulcata Zone, when the Hangenberg mass extinction occurred. We attribute the nitrogen cycle anomaly to enhanced microbial nitrogen fixation, which was likely a consequence of intensified seawater anoxia associated with increased denitrification, as well as upwelling of anoxic ammonium-bearing waters. Negative excursions in the δ13 Ccarb and δ13 Corg values were identified in the Middle Si. praesulcata Zone and likely resulted from intense deep ocean upwelling that amplified nutrient fluxes and delivered 13 C-depleted anoxic water masses. Decreased δ34 S values during the Middle Si. praesulcata Zone suggests an increasing contribution of water-column sulfate reduction under euxinic conditions. Contributions of organic matter produced by anaerobic metabolisms to the deposition of shallow carbonate in the Upper Si. praesulcata Zone is recorded by the nadir of δ13 Corg values associated with maximal △13 C. The integrated δ15 N-δ13 C-δ34 S data suggest that significant ocean-redox variation was recorded in South China during the D-C transition; and that this prominent fluctuation was likely associated with intense upwelling of deep anoxic waters. The temporal synchrony between the development of euxinia/anoxia and the Hangenberg Event indicates that the redox oscillation was a key factor triggering manifestations of the biodiversity crisis.

Epo inhibits the fibrosis and migration of Müller glial cells induced by TGF-ß and high glucose.

BACKGROUND: In proliferative diabetic retinopathy (PDR), Müller glial cells (MGCs) acquire migratory ability and exhibit a fibroblast-like phenotype. These activated MGCs contribute to the formation of epiretinal membrane, which will stretch the retina, and cause retinal detachment and vitreous hemorrhage. Erythropoietin (Epo) is now found effective in ameliorating renal fibrosis by inhibiting epithelial-to-mesenchymal transition of tubular epithelial cells. This study is undertaken to determine whether Epo has an effect in inhibiting MGCs activation to attenuate epiretinal membrane formation in PDR. METHOD: MIO-M1 cell line was used in this study. As a pilot test to determine the most efficient treatment time and concentration of Epo, levels of connective tissue growth factor (CTGF) and transforming growth factor-ß (TGF-ß) were measured by real-time PCR, after treatment with Epo on MGCs cultured in high glucose. MGCs were cultured in high glucose and normal glucose for 2 days, with or without TGF-ß as a pro-fibrogenic cytokine. Epo was introduced at the same time. Immunofluorescence targeting α-smooth muscle actin (α-SMA), fibronectin, and glial fibrillary acidic protein (GFAP) was performed to explore the cell phenotype. Matrix metalloproteinase 9 (MMP9) mRNA level was detected by real-time PCR. Protein levels of CTGF and cytoskeletal proteins like α-SMA and fibronectin were measured by enzyme-linked immunosorbent assay (ELISA) and Western blot respectively. Wound-healing assay was applied to evaluate the migratory ability of MGCs, and actin-tracker green was used to draw the structure of F-actin in MGCs. RESULTS: After being seeded into high-glucose medium containing TGF-ß, MGCs expressed a larger amount of MMP9 mRNA as well as α-SMA, fibronectin at protein level. They secreted more CTGF, and their F-actin reorganized in a parallel manner and showed a stronger ability to migrate. In addition, these changes, including mRNA and protein expression, F-actin assembling, and cell migration, could be attenuated significantly by Epo treatment. CONCLUSION: High glucose together with TGF-ß promote MGCs to exhibit a fibroblast-like phenotype and develop a greater migratory ability. These changes can be inhibited by Epo, which therefore may contribute to the controlling of epiretinal membrane formation.

The protective effect of erythropoietin on the retina.

Erythropoietin (Epo) was once considered to be a regulator of erythropoiesis by controlling the apoptosis, proliferation and differentiation of erythroid precursor cells over an extended period of time. However, the expression of Epo and Epo receptor (Epo-R) occurs in the brain and retina in addition to the kidney. These expression behaviors lead to physiological effects in addition to hematocrit elevation. In this review we discuss the protective effect of Epo on retinal cells.

Sudden visual loss in the untreated eye of a patient with neovascular glaucoma following an intravitreal bevacizumab injection: A case report.

The current study presents the case of a patient with a rare adverse event characterized by sudden vision loss in the untreated eye following an intravitreal injection of bevacizumab for neovascular glaucoma (NVG). The patient was diagnosed with NVG refractory to Ahmed glaucoma valve implantation and a vitreous hemorrhage in the right eye, which was treated with 1.25 mg intravitreal bevacizumab. Ten days after the bevacizumab injection, the left eye exhibited sudden visual loss. The patient's best-corrected visual acuity (BCVA) decreased from 80 to 25 letters [Early Treatment Diabetic Retinopathy Study (ETDRS) chart]. A fundus examination revealed a swollen optic disk with unclear boundaries, retinal hemorrhages and thinning retinal vessels. Fundus fluorescein angiography (FA) identified hyperfluorescence in the optic disk and an enlarged foveal avascular zone. The visual field revealed quadrantal defects that confirmed the diagnosis of anterior ischemic optic neuropathy associated with ischemic maculopathy. Six months later, following medical treatment, the patient's BCVA was increased to 44 letters. However, a clinical examination found neovessels with one papilla disk (PD) above the disk. Laser photocoagulation treatment was administered immediately. The area of neovessels above the disk was reduced to 1/4 PD at the last follow-up. In conclusion, although intravitreal anti-vascular endothelial growth factor (Bevacizumab) is an effective treatment for neovascular ocular diseases, its adverse effects must be taken into consideration for the treatment of NVG. Photocoagulation remains an effective treatment for proliferative diabetic retinopathy.

Erythropoietin receptor positive circulating progenitor cells and endothelial progenitor cells in patients with different stages of diabetic retinopathy.

OBJECTIVE: To investigate the possible involvement of erythr opoietin (EPO)/erythropoietin receptor (EPOR) system in neovascularization and vascular regeneration in diabetic retinopathy (DR). METHODS: EPOR positive circulating progenitor cells (CPCs: CD34(+)) and endothelial progenitor cells (EPCs: CD34(+)KDR(+)) were assessed by flow cytometry in type 2 diabetic patients with different stages of DR. The cohort consisted of age- and sex-matched control patients with out diabetes ( n=7),non-proliferative DR (NPDR, n=7),non-proliferative DR (PDR, n=8), and PDR complicated with diabetic nephr opathy (PDR-DN, n=7). RESULTS: The numbers of EPOR(+) CPCs and EPOR(+) EPCs were reduced remarkably in NPDR compared with the control group (both Pü0.01), whereas rebounded in PDR and PDR-DN groups in varyingdegrees. Similar changes were observed in respect of the proportion of EPOR(+)CPCs in CPCs (NPDR vs. control, Pü0.01) and that of EPOR(+) EPCs in EPCs (NPDR vs. control, Pü0.05). CONCLUSION: Exogenous EPO, mediated via the EPO/EPOR system of EPCs, may alleviate the impaired vascular regeneration in NPDR, whereas it might aggravate retinal neovascularization in PDR due to a rebound of EPOR(+)EPCs associated with ischemia.

EPO reduces reactive gliosis and stimulates neurotrophin expression in Muller cells.

To characterize Müller cell-mediated neuroprotective and neurotrophic functions of the erythropoietin (EPO)/EPO receptor (EpoR) system in diabetic rat retina. A single intravitreal injection of EPO (8 mU/eye) was administered in rats 4 or 24 weeks after diabetes onset. The results showed that intravitreal EPO ameliorated the up-regulation of GFAP and vimentin in the diabetic retina evaluated by immunofluorescence and Western blotting; but up-regulated BDNF and CNTF expressions, quantified by real-time PCR and ELISA, in the 24-week diabetic rat retinas. In vitro, BDNF and CNTF expressions were stimulated by EPO through both extracellular signal-regulated kinase1/2 (ERK1/2) and Akt pathways. The neuro-regenerative function of EPO, as indicated by promotion of neurite outgrowth, was corroborated in vitro. BDNF was involved in EPO-induced neurite outgrowth of primary rat retinal neurons. Exogenous EPO exerts neuroprotective and neurotrophic functions by attenuating reactive gliosis and promoting neurotrophic factors in Muller cells in diabetic retina. Signaling pathways that are responsible for these Muller cell-mediated EPO/EpoR functions may be therapeutic targets for diabetic retinopathy.

EPO attenuates inflammatory cytokines by Muller cells in diabetic retinopathy.

Diabetic retinopathy (DR) is a chronic, low-grade inflammatory disease. We aimed to investigate the regulatory effects of erythropoietin (EPO) on the inflammatory cytokine production by Muller cells under the condition of DR. The expression levels of TNF-alpha, IL-1beta, IL-6 and VEGF in cultured rat Muller cells were enhanced by 1 mM glyoxal. The elevated TNF-alpha and IL-1beta, but not IL-6 and VEGF, were decreased by 2 U/ml EPO as detected by real-time PCR and ELISA. Moreover, the activity of AP-1 but not NF-kappaB was modulated by glyoxal and EPO. Intravitreal injection of EPO performed 24 h prior to sacrifice significantly reduced TNF-alpha and IL-1beta production while moderately attenuating IL-6 and VEGF in the retinas of streptozotocin-induced diabetic rats. Furthermore, Muller cells were identified as the main source of IL-1beta production as indicated by co-localization of IL-1beta and CRALBP in situ. These findings implicate therapeutic potential of EPO in the amelioration of inflammation in diabetic retinas.

Anti-VEGF effects of intravitreal erythropoietin in early diabetic retinopathy.

In the present study, a single intravitreal erythropoietin (EPO) to diabetic rats produced therapeutic effects on blood-retinal barrier (BRB) function and neuronal survival at different time courses of retinopathy. In parallel, the hypoxia-inducible factor 1 alpha (HIF-1 alpha) pathway has been quantitatively studied, including VEGF-A, endogenous EPO, EPO receptor (EpoR), prolyl hydroxylases (PHD1-3) and von Hippel-Lindau tumor suppressor (VHL). The mRNA levels of HIF-1 alpha, VEGF-A, endogenous EPO, PHD1-3 and VHL are all up-regulated in the diabetic retina, and suppressed by exogenous EPO. The increased protein levels of HIF-1 alpha, VEGF-A, and endogenous EPO found in diabetic retinas also have been down-regulated by exogenous EPO. The results demonstrate that the HIF-1 pathway is activated in the retina in early diabetes, but is negatively regulated by a feedback loop following the administration of exogenous EPO. Exogenous EPO at pharmacologic levels leads to suppression of VEGF and in turn, restoration of the normal functions of BRB in a time-dependent manner. In the diabetic retina, the same level of exogenous EPO that inhibits VEGF also exerted neuronal protection.