Trehalose is a naturally occurring disaccharide that has gained attention for its ability to induce cellular autophagy and mitigate diseases related to pathological protein aggregation. Despite decades of ubiquitous use as a nutraceutical, preservative, and humectant, its mechanism of action remains elusive. Here, we showed that trehalose inhibited members of the SLC2A (also known as GLUT) family of glucose transporters. Trehalose-mediated inhibition of glucose transport induced AMPK (adenosine 5′-monophosphate-activated protein kinase)-dependent autophagy regression of hepatic steatosis in vivo, and a reduction in the accumulation of lipid droplets in primary murine hepatocyte cultures. Our data indicated that, by inhibiting glucose transport, trehalose triggers beneficial cellular autophagy.

No abstract

Tamm-Horsfall protein (THP) is a glycoprotein normally targeted to the apical membrane domain of the kidney's thick ascending limbs (TAL). We previously showed that THP of TAL confers protection to proximal tubules against acute kidney injury (AKI) via a possible cross talk between the two functionally distinct tubular segments. However, the extent, timing, specificity, and functional effects of basolateral translocation of THP during AKI remain unclear. Using an ischemia-reperfusion (IRI) model of murine AKI, we show here that, while THP expression in TAL is downregulated at the peak of injury, it is significantly upregulated 48 h after IRI. Confocal immunofluorescence and immunoelectron microscopy reveal a major redirection of THP during recovery from the apical membrane domain of TAL towards the basolateral domain, interstitium, and basal compartment of S3 segments. This corresponds with increased THP in the serum but not in the urine. The overall epithelial polarity of TAL cells does not change, as evidenced by correct apical targeting of Na(+)-K(+)-2Cl cotransporter (NKCC2) and basolateral targeting of Na(+)-K(+)-ATPase. Compared with the wild-type, THP(-/-) mice show a significantly delayed renal recovery after IRI, due possibly to reduced suppression by THP of proinflammatory cytokines and chemokines such as monocyte chemoattractant protein-1 during recovery. Taken together, our data suggest that THP redistribution in the TAL after AKI is a protein-specific event and its increased interstitial presence negatively regulates the evolving inflammatory signaling in neighboring proximal tubules, thereby enhancing kidney recovery. The increase of serum THP may be used as a prognostic biomarker for recovery from AKI.

The purpose of this study was to evaluate the effects of interferon-␥ (IFN-␥) alone and in combination with interleukin 1␤ (IL-1␤) on inducible nitric-oxide synthase (iNOS) mRNA and protein expression, nitrite production, and insulin secretion by islets of Langerhans. Treatment of rat islets with IL-1␤ results in a concentration-dependent increase in the production of nitrite that is maximal at 5 units/ml. Individually, 0.1 unit/ml IL-1␤ or 150 units/ml rat IFN-␥ do not stimulate iNOS expression or nitrite production by rat islets; however, in combination, these cytokines induce the expression of iNOS and the production of nitrite to levels similar in magnitude to the individual effects of 5 units/ml IL-1␤. The islet ␤-cell, selectively destroyed during insulin-dependent diabetes mellitus, appears to be one islet cellular source of iNOS as 150 units/ml rat IFN-␥ and 0.1 unit/ml IL-1␤ induced similar effects in primary ␤-cells purified by fluorescence-activated cell sorting and in the rat insulinoma cell line, RINm5F. iNOS expression and nitrite production by rat islets in response to 150 units/ml rat IFN-␥ and 0.1 unit/ml IL-1␤ are correlated with an inhibition of insulin secretion and islet degeneration that are prevented by the iNOS inhibitor aminoguanidine. The mechanism by which IFN-␥ increases the sensitivity of ␤-cells for IL-1-induced iNOS expression appears to be associated with an increase in the stability of iNOS mRNA. Last, cellular damage during physical dispersion of islets results in the release of sufficient amounts of IL-1␤ to induce iNOS expression and nitrite production in the presence of exogenously added rat IFN-␥. The cellular source of IL-1␤ under these conditions is believed to be resident islet macrophages as depletion of macrophages prior to dispersion prevents IFN-␥-induced iNOS expression and nitrite formation by dispersed islet cells. These studies show that the T-lymphocyte cytokine, IFN-␥, increases the sensitivity of rat islets to the effects of IL-1␤ on iNOS expression and nitrite production by 10-fold, in part, through the stabilization of iNOS mRNA. Our studies also support an effector role for IFN-␥, in concert with resident islet macrophage release of IL-1␤, in mediating ␤-cell destruction during the development of autoimmune diabetes.Insulin-dependent diabetes mellitus is an autoimmune disease characterized by the selective destruction of insulin secreting ␤-cells found in islets of Langerhans. Many lines of evidence support a role for the involvement of cytokines as effector molecules that participate in the development of diabetes. Mandrup-Poulsen et al.(1) first showed that treatment of isolated rat islets with conditioned media derived from activated mononuclear cells results in a potent inhibition of insulin secretion followed by islet destruction. The active component of this conditioned media was determined to be the cytokine IL-1 1 (2). IL-1-induced inhibition of insulin secretion is both timeand concentration-dependent and requires mRNA transcription and new protein ...

The effects of double-stranded RNA (synthetic polyinosinic-polycytidylic acid; poly(I-C)) on macrophage expression of inducible nitric-oxide synthase (iNOS), production of nitric oxide, and release of interleukin-1 (IL-1) were investigated. Individually, poly(I-C), interferon-␥ (IFN-␥), and lipopolysaccharide (LPS) stimulate nitrite production and iNOS expression by RAW 264.7 cells. In combination, the effects of poly(I-C) ؉ IFN-␥ are additive, while poly(I-C) does not further potentiate LPS-induced nitrite production. These results suggest that poly(I-C) and LPS may stimulate iNOS expression by similar signaling pathways, which may be independent of pathways activated by IFN-␥. LPS-induced iNOS expression is associated with the activation of NF-B. We show that inhibition of NF-B by pyrrolidinedithiocarbamate prevents poly(I-C) ؉ IFN-␥-, poly(I-C) ؉ LPS-, and LPS-induced iNOS expression, nitrite production and IB degradation by RAW 264.7 cells. The effects of poly(I-C) on iNOS ex-pression appear to be cell-type specific. Poly(I-C), alone or in combination with IFN-␥, does not stimulate, nor does poly(I-C) potentiate, IL-1-induced nitrite production by rat insulinoma RINm5F cells. In addition, we show that the combination of poly(I-C) ؉ IFN-␥ stimulates iNOS expression, nitrite production, IB degradation, and the release of IL-1 by primary mouse macrophages, and these effects are prevented by pyrrolidinedithiocarbamate. These findings indicate that double-stranded RNA, in the presence of IFN-␥, is a potent activator of macrophages, stimulating iNOS expression, nitrite production, and IL-1 release by a mechanism which requires the activation of NF-B.