Abiotic synthesis of graphitic carbons in the Eoarchean Saglek-Hebron metasedimentary rocks.

Graphite in metasedimentary rocks of the Eoarchean Saglek-Hebron Gneiss Complex (Canada) is depleted in 13C and has been interpreted as one of the oldest traces of life on Earth. The variation in crystallinity of this oldest graphitic carbon could possibly confirm the effect of metamorphism on original biomass, but this is still unexplored. Here, we report specific mineral associations with graphitic carbons that also have a range of crystallinity in the Saglek-Hebron metasedimentary rocks. Petrographic, geochemical and spectroscopic analyses in the Saglek-Hebron banded iron formations suggest that poorly crystalline graphite is likely deposited from C-H-O fluids derived from thermal decomposition of syngenetic organic matter, which is preserved as crystalline graphite during prograde metamorphism. In comparison, in the Saglek-Hebron marble, disseminations of graphite co-occur with carbonate and magnetite disseminations, pointing to abiotic synthesis of graphitic carbons via decarbonation. Our results thus highlight that variably crystalline graphitic carbons in the Saglek-Hebron metasedimentary rocks are potential abiotic products on early Earth, which lay the groundwork for identifying the preservation of prebiotic organic matter through metamorphism on Earth and beyond.

Irisin Prevents Cell Death in High Glucose via NLRP3 Inhibition.

Background: Impaired cardiac microvascular function has been implied in the pathophysiology of diabetic cardiovascular disease. However, the specific mechanism remains to be determined. Pyroptosis is a type of cell death that differs from apoptosis and autophagy. It is caused by the formation of plasma membrane pores through amino-terminal fragments of Gasdermin D (GSDMD), leading to the secretion of IL-1ß and IL-18. Recent studies have shown that irisin, a myokine cleaved by the extracellular domain of FNDC5, plays a protective role in cardiovascular diseases. Here, we investigated the potential role of pyroptosis on the cardiac microvascular endothelial cells (CMECs) injury induced by high glucose (HG) and further determined the protective effect of irisin on pyroptosis. Methods: CMECs were cultured with normal glucose (control group, 5.5 mM) and high glucose (25 mM) medium for 12, 24, and 48 h respectively. The pyroptosis of CMECs was measured by immunofluorescence staining, ELISA, and Western blot assays. Moreover, the apoptosis level was determined by flow cytometry and TUNEL staining. Results: Our results showed that HG promoted apoptosis and pyroptosis. However, irisin reversed the increased apoptosis and pyroptosis. To investigate the underlying mechanism, we overexpressed the NLRP3 protein. We found the protective effect of irisin on apoptosis and pyroptosis was abolished by NLRP3 over-expression. Conclusions: Our data suggest that irisin protects CMECs against apoptosis and pyroptosis, at least in part, by inhibiting NLRP3 inflammasome.