A Na+-and C1-coupled serotonin (5-hydroxytryptamine, SHT) transporter is expressed on human neuronal, platelet, placental, and pulmonary membranes. The brain 5HT transporter appears to be a principal site of action of therapeutic antidepressants and may mediate behavioral and/or toxic effects of cocaine and amphetamines. Oligonucleotides derived from consensus transporter sequences were used to identify human placental cDNAs highly related to the rat brain 5HT carrier. Transfection of one of these cDNAs into HeLa cells yields a high-affinity (Km = 463 nM), Na+-and Cl--dependent 5HT transport activity which can be blocked by selective 5HT transport inhibitors, including paroxetine, fluoxetine, and imipramine, and which is antagonized by cocaine and amphetamine. Sequence analysis reveals a 630-amino acid open reading frame bearing 92% identity to the cloned rat brain 5HT transporter, with identical predicted topological features and conserved sites for posttranslational modifications. Unlike the rodent, where a single mRNA appears to encode 5HT transporters, multiple hybridizing RNAs are observed in human placenta and lung. Somatic cell hybrid and in situ hybridization studies are consistent, however, with a single gene encoding the human 5HT transporter, localized to chromosome 17q11.1-17q12.The endogenous indoleamine serotonin (5-hydroxytryptamine, 5HT) is a neurotransmitter in the central and peripheral nervous system (1, 2). Following release, 5HT is actively cleared from synaptic spaces by a high-affinity (Km 0.5 ,uM), Na+-and Cl--dependent transporter localized in presynaptic neuronal membranes (3-5). Transport of serotonin is exquisitely sensitive to nanomolar concentrations of tricyclic and heterocyclic antidepressants, including imipramine, fluoxetine, and paroxetine (6), which are thought to bind directly to the 5HT carrier (7-10), presumably constituting the initial step in their therapeutic actions. In the periphery, platelet (11), placental (12), and pulmonary (13) plasma membranes exhibit a 5HT transporter whose ionic and pharmacologic sensitivities are highly similar to those described for the neuronal transporter. In particular, plasma membrane vesicle studies reveal central and peripheral 5HT carriers to be dependent upon extracellular Na+ and Cl-, stimulated by intracellular K+, and antagonized competitively by antidepressants (5, 11, 14-17). These properties serve to distinguish the plasma membrane 5HT transporter from the monoamine transporter present in intracellular secretory vesicles, which utilizes a transmembrane H+ gradient in an imipramine-insensitive, but reserpine-sensitive, manner to sequester amines, including 5HT, for release (18).The therapeutic utility of 5HT transport antagonists in the treatment of depression, obsessive-compulsive disorder, and sleep and eating disorders (19) has contributed to an emphasis on central serotonergic dysfunction within the monoamine theory of affective disorders (20). While not a universal finding, reported reductions in platelet or brain 5H...

Transforming growth factor-β1 (TGF-β1) is established to be involved in the pathogenesis of diabetic nephropathy. The diabetic milieu enhances oxidative stress and induces the expression of TGF-β1. TGF-β1 promotes cell hypertrophy and extracellular matrix accumulation in the mesangium, which decreases glomerular filtration rate and leads to chronic renal failure. Recently, TGF-β1 has been demonstrated to regulate urinary albumin excretion by both increasing glomerular permeability and decreasing reabsorption in the proximal tubules. TGF-β1 also increases urinary excretion of water, electrolytes and glucose by suppressing tubular reabsorption in both normal and diabetic conditions. Although TGF-β1 exerts hypertrophic and fibrogenic effects in diabetic nephropathy, whether suppression of the function of TGF-β1 can be an option to prevent or treat the complication is still controversial. This is partly because adrenal production of mineralocorticoids could be augmented by the suppression of TGF-β1. However, differentiating the molecular mechanisms for glomerulosclerosis from those for the suppression of the effects of mineralocorticoids by TGF-β1 may assist in developing novel therapeutic strategies for diabetic nephropathy. In this review, we discuss recent findings on the role of TGF-β1 in diabetic nephropathy.

Nephropathy develops in many but not all patients with longstanding type 1 diabetes. Substantial efforts to identify genotypic differences explaining this differential susceptibility have been made, with limited success. Here, we show that the expression of the transforming growth factor β1 gene (Tgfb1) affects the development of diabetic nephropathy in mice. To do this we genetically varied Tgfb1 expression in five steps, 10%, 60%, 100%, 150%, and 300% of normal, in mice with type 1 diabetes caused by the Akita mutation in the insulin gene (Ins2 Akita ). Although plasma glucose levels were not affected by Tgfb1 genotype, many features of diabetic nephropathy (mesangial expansion, elevated plasma creatinine and urea, decreased creatinine clearance and albuminuria) were progressively ameliorated as Tgfb1 expression decreased and were progressively exacerbated when expression was increased. The diabetic 10% hypomorphs had comparable creatinine clearance and albumin excretion to wild-type mice and no harmful changes in renal morphology. The diabetic 300% hypermorphs had ∼1/3 the creatinine clearance of wild-type mice, >20× their albumin excretion, ∼3× thicker glomerular basement membranes and severe podocyte effacement, matching human diabetic nephropathy. Switching Tgfb1 expression from low to high in the tubules of the hypomorphs increased their albumin excretion more than 10-fold but creatinine clearance remained high. Switching Tgfb1 expression from low to high in the podocytes markedly decreased creatinine clearance, but minimally increased albumin excretion. Decreasing expression of Tgfb1 could be a promising option for preventing loss of renal function in diabetes.aldosterone | glomerular filtration rate | glomerulosclerosis | megalin | nephrin D iabetes is the number one cause of end-stage renal disease in the United States and many other developed countries. However, despite having similar levels of blood glucose only 20-40% of all diabetic patients develop diabetic nephropathy. In diabetic nephropathy, increased expression of transforming growth factor β1 (TGFβ1) has been demonstrated to promote accumulation of extracellular matrix components (1), apoptosis (2), dedifferentiation of podocytes (3), and epithelial-mesenchymal transition of proximal tubules (4), all of which are thought to facilitate a decline in nephron number and renal function.Tgfb1-null mice on a mixed genetic background show severe multiorgan inflammation with massive infiltration of lymphocytes and macrophages that culminates in death by 3-4 wk of age (5, 6). Their death effectively prevents determining whether absence of TGFβ1 influences the development of nephropathy. To overcome this problem and also to allow the study of the effects of above-normal TGFβ1, we have generated mice with five genetically graded levels of TGFβ1, and have made them diabetic with the Ins2 Akita mutation, which causes pancreatic beta-cell dysfunction and type 1 diabetes.Here we show that the features characteristic of diabetic nephropathy are progressively ...

Human genome-wide association studies have demonstrated that polymorphisms in the engulfment and cell motility protein 1 gene (ELMO1) are strongly associated with susceptibility to diabetic nephropathy. However, proof of causation is lacking. To test whether modest changes in its expression alter the severity of the renal phenotype in diabetic mice, we have generated mice that are type 1 diabetic because they have the Ins2Akita gene, and also have genetically graded expression of Elmo1 in all tissues ranging in five steps from ∼30% to ∼200% normal. We here show that the Elmo1 hypermorphs have albuminuria, glomerulosclerosis, and changes in the ultrastructure of the glomerular basement membrane that increase in severity in parallel with the expression of Elmo 1. Progressive changes in renal mRNA expression of transforming growth factor β1 (TGFβ1), endothelin-1, and NAD(P)H oxidase 4 also occur in parallel with Elmo1, as do the plasma levels of cystatin C, lipid peroxides, and TGFβ1, and erythrocyte levels of reduced glutathione. In contrast, Akita type 1 diabetic mice with below-normal Elmo1 expression have reduced expression of these various factors and less severe diabetic complications. Remarkably, the reduced Elmo1 expression in the 30% hypomorphs almost abolishes the pathological features of diabetic nephropathy, although it does not affect the hyperglycemia caused by the Akita mutation. Thus, ELMO1 plays an important role in the development of type 1 diabetic nephropathy, and its inhibition could be a promising option for slowing or preventing progression of the condition to end-stage renal disease.reactive oxygen species | 3′-untranslated region | fibrosis

Recent findings have suggested that the vertebrate trp family of channel proteins is the structural basis for Ca 2+ influx through the capacitative calcium entry (CCE) pathway. We have discerned, in bovine aortic endothelial cells, the concomitant expression of four such vertebrate genes: trp-1 (two splice variants), trp-3, trp-4 and trp-5. Exogenous hormones rendered dynamic effects on the transcript levels of these genes. Most notably, ß-estradiol significantly down-regulated trp-4 while frans-retinoic acid dramatically up-regulated trp-5; yet these hormones rendered little change in CCE. These findings suggest that the extent of a given trp channel's participation in CCE is not reflected in alterations of its transcript level.