Diet-induced obesity impairs AKT signalling in the retina and causes retinal degeneration

Retinopathy, a common complication of diabetes, is characterized by an unbalanced production of nitric oxide (NO), a process regulated by nitric oxide synthase (NOS). We hypothesized that retinopathy might stem from changes in the insulin receptor substrate (IRS)/PI3K/AKT pathway and/or expression of NOS isoforms. Thus, we analysed the morphology and apoptosis index in retinas of obese rats in whom insulin resistance had been induced by a high-fat diet (HFD). Immunoblotting analysis revealed that the retinal tissue of HFD rats had lower levels of AKT(1) , eNOS and nNOS protein than those of samples taken from control animals. Furthermore, immunohistochemical analyses indicated higher levels of iNOS and 4-hydroxynonenal and a larger number of apoptotic nuclei in HFD rats. Finally, both the inner and outer retinal layers of HFD rats were thinner than those in their control counterparts. When considered alongside previous results, these patterns suggest two major ways in which HFD might impact animals: direct activity of ingested fatty acids and/or via insulin-resistance-induced changes in intracellular pathways. We discuss these possibilities in further detail and advocate the use of this animal model for further understanding relationships between retinopathy, metabolic syndrome and type 2 diabetes.

UPR induces transient burst of apoptosis in islets of early lactating rats through reduced AKT phosphorylation via ATF4/CHOP stimulation of TRB3 expression

Endocrine pancreas from pregnant rats undergoes several adaptations that comprise increase in β-cell number, mass and insulin secretion, and reduction of apoptosis. Lactogens are the main hormones that account for these changes. Maternal pancreas, however, returns to a nonpregnant state just after the delivery. The precise mechanism by which this reversal occurs is not settled but, in spite of high lactogen levels, a transient increase in apoptosis was already reported as early as the 3rd day of lactation (L3). Our results revealed that maternal islets displayed a transient increase in DNA fragmentation at L3, in parallel with decreased RAC-alpha serine/threonine-protein kinase (AKT) phosphorylation (pAKT), a known prosurvival kinase. Wortmannin completely abolished the prosurvival action of prolactin (PRL) in cultured islets. Decreased pAKT in L3-islets correlated with increased Tribble 3 (TRB3) expression, a pseudokinase inhibitor of AKT. PERK and eIF2α phosphorylation transiently increased in islets from rats at the first day after delivery, followed by an increase in immunoglobulin heavy chain-binding protein (BiP), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP) in islets from L3 rats. Chromatin immunoprecipitation (ChIP) and Re-ChIP experiments further confirmed increased binding of the heterodimer ATF4/CHOP to the TRB3 promoter in L3 islets. Treatment with PBA, a chemical chaperone that inhibits UPR, restored pAKT levels and inhibited the increase in apoptosis found in L3. Moreover, PBA reduced CHOP and TRB3 levels in β-cell from L3 rats. Altogether, our study collects compelling evidence that UPR underlies the physiological and transient increase in β-cell apoptosis after delivery. The UPR is likely to counteract prosurvival actions of PRL by reducing pAKT through ATF4/CHOP-induced TRB3 expression.

TRPV1 receptors are involved in protein nitration and Müller cell reaction in the acutely axotomized rat retina

We report here the protein expression of TRPV1 receptor in axotomized rat retinas and its possible participation in mechanisms involved in retinal ganglion cell (RGC) death. Adult rats were subjected to unilateral, intraorbital axotomy of the optic nerve, and the retinal tissue was removed for further processing. TRPV1 total protein expression decreased progressively after optic nerve transection, reaching 66.2% of control values 21 days after axotomy. The number of cells labeled for TRPV1 in the remnant GCL decreased after 21 days post-lesion (to 63%). Fluoro-Jade B staining demonstrated that the activation of TRPV1 in acutely-lesioned eyes elicited more intense neuronal degeneration in the GCL and in the inner nuclear layer than in sham-operated retinas. A single intraocular injection of capsazepine (100 μM), a TRPV1 antagonist, 5 days after optic nerve lesion, decreased the number of GFAP-expressing Müller cells (72.5% of control values) and also decreased protein nitration in the retinal vitreal margin (75.7% of control values), but did not affect lipid peroxidation. Furthermore, retinal explants were treated with capsaicin (100 μM), and remarkable protein nitration was then present, which was reduced by blockers of the constitutive and inducible nitric oxide synthases (7-NI and aminoguanidine, respectively). TRPV1 activation also increased GFAP expression, which was reverted by both TRPV1 antagonism with capsazepine and by 7-NI and aminoguanidine. Given that Müller cells do not express TRPV1, we suppose that the increased GFAP expression in these cells might be elicited by TRPV1 activation and by its indirect effect upon nitric oxide overproduction and peroxynitrite formation. We incubated Fluorogold pre-labeled retinal explants in the presence of capsazepine (1 μM) during 48 h. The numbers of surviving RGCs stained with fluorogold and the numbers of apoptotic cells in the GCL detected with TUNEL were similar in lesioned and control retinas. We conclude that TRPV1 receptor expression decreased after optic nerve injury due to death of TRPV1-containing cells. Furthermore, these data indicate that TRPV1 might be involved in intrinsic protein nitration and Müller cell reaction observed after optic nerve injury.

Ontogenetic expression of the vanilloid receptors TRPV1 and TRPV2 in the rat retina

The present study aimed to analyze the gene and protein expression and the pattern of distribution of the vanilloid receptors TRPV1 and TRPV2 in the developing rat retina. During the early phases of development, TRPV1 was found mainly in the neuroblastic layer of the retina and in the pigmented epithelium. In the adult, TRPV1 was found in microglial cells, blood vessels, astrocytes and in neuronal structures, namely synaptic boutons of both retinal plexiform layers, as well as in cell bodies of the inner nuclear layer and the ganglion cell layer. The pattern of distribution of TRPV1 was mainly punctate, and there was higher TRPV1 labeling in the peripheral retina than in central regions. TRPV2 expression was quite distinct. Its expression was virtually undetectable by immunoblotting before P1, and that receptor was found by immunohistochemistry only by postnatal day 15 (P15). RNA and protein analysis showed that the adult levels are only reached by P60, which includes small processes in the retinal plexiform layers, and labeled cellular bodies in the inner nuclear layer and the ganglion cell layer. There was no overlapping between the signal observed for both receptors. In conclusion, our results showed that the patterns of distribution of TRPV1 and TRPV2 are different during the development of the rat retina, suggesting that they have specific roles in both visual processing and in providing specific cues to neural development.

Differential expression of connexins during histogenesis of the chick retina

Gap junction (GJ) channels couple adjacent cells, allowing transfer of second messengers, ions, and molecules up to 1 kDa. These channels are composed by a multigene family of integral membrane proteins called connexins (Cx). In the retina, besides being essential circuit element in the visual processing, GJ channels also play important roles during its development. Herein, we analyzed Cx43, Cx45, Cx50, and Cx56 expression during chick retinal histogenesis. Cx exhibited distinct expression profiles during retinal development, except for Cx56, whose expression was not detected. Cx43 immunolabeling was observed at early development, in the transition of ventricular zone and pigmented epithelium. Later, Cx43 was seen in the outer plexiform and ganglion cell layers, and afterwards also in the inner plexiform layer. We observed remarkable changes in the phosphorylation status of this protein, which indicated modifications in functional properties of this Cx during retinal histogenesis. By contrast, Cx45 showed stable gene expression levels throughout development and ubiquitous immunoreactivity in progenitor cells. From later embryonic development, Cx45 was mainly observed in the inner retina, and it was expressed by glial cells and neurons. In turn, Cx50 was virtually absent in the chick retina at initial embryonic phases. Combination of PCR, immunohistochemistry and Western blot indicated that this Cx was present in differentiated cells, arising in parallel with the formation of the visual circuitry. Characterization of Cx expression in the developing chick retina indicated particular roles for these proteins and revealed similarities and differences when compared to other species.

Developmental expression of cannabinoid receptors in the chick retinotectal system

The cannabinoid system has been suggested to participate in processes such as antinociception, cognition, motor control, and, more recently, development of the nervous system. This study describes the expression of the CB1 cannabinoid receptor in the developing chick retina and optic tectum by means of conventional immunoperoxidase protocols. CB1 immunoreactivity was initially detected around the embryonic day 4 (E4) in both the retina and tectum. In the retina, CB1 immunoreactivity was first observed in presumptive ganglion cells and, subsequently, in the inner plexiform layer and two populations of neurons of the inner nuclear layer. The post-hatched chick exhibited a pattern of staining that included four sublayers of the inner plexiform layer, a few stained cells in the ganglion cell layer, and labeled neurons both in the inner and central parts of the inner nuclear layer. The latter two types of neurons appear to be amacrine and bipolar cells, respectively. In the tectum, CB1 first appeared in its most superficial zone and later in several tectal laminae, including a white matter layer (stratum album centrale; Cajal's layer 14). There was a remarkable and transient increase of labeling at E10, followed by a continuous reduction of staining until E18. In the post-hatched chick, tectal staining was mostly confined to layers 2-3 and 5-6. Stained perikarya were seldom observed in the tectum at any stage. These data are in agreement with a possible developmental function of CB1, as it is expressed several days before synaptogenesis ensues and exhibits transient expression in the optic tectum.

Acute renal failure of medical type in an elderly population

One hundred and nine unselected patients with Acute Renal Failure (ARF) of medical aetiology were hospitalized at the Nephrological Unit of Policlinico University Hospital (Modena) during a 30-month period. ARF was considered as a rapid increase of serum creatinine > 2mg/dl over the baseline level or the doubling of pre-existing value in chronic renal failure. Mean age of patients was 67+/-17 years and median age was 72; 64.2% needing dialytic treatment. Four main causes of ARF were identified: 33 patients had reduced renal perfusion by dehydration, hypotension etc.; 20 multifactorial aetiology; 14 biopsy-investigated renal parenchymal diseases and 39 had drug-related acute renal failure (D-ARF). The clinical outcome was significantly worse in elderly patients as regard mortality (P < 0.02), chronic dialytic treatment (P < 0.04) and complete recovery (P < 0.004). The mean age of D-ARF patients was significantly greater than remaining ARF patients (72.6+/-12.8 vs 63.2+/-18.5: P < 0.004. Nonsteroidal antiinflammatory drugs (NSAIDs) and ACE-inhibitors (Ace-i) caused ARF in 24 and 8 patients respectively. Elderly age, vascular disease and monoclonal gammopathy represented the main risk factors and were significantly more frequent in D-ARF patients (P<001, <0.01, <0.04 respectively). Our data confirm the high susceptibility of ageing kidneys to nephrotoxic damage caused by drugs affecting glomerular autoregulation by microvascular mechanisms. Greater attention to renal changes in ageing and an increased dissemination of preventative measures among nephrologists, could reduce the incidence of these serious and potentially lethal diseases.

Chronic dialysis in patients with systemic amyloidosis: the experience in northern Italy

The clinical outcome of 61 patients with renal amyloidosis treated with chronic dialysis was reviewed. Eighteen patients, 4 with primary or AL amyloidosis and 14 with reactive or AA amyloidosis, died within one month from starting treatment. The other 43 patients were treated with dialysis for 3 to 199 months and are the object of this study. Sixteen patients had AL amyloidosis and 27 had AA amyloidosis. Thirty-five patients were treated with hemodialysis (HD) for a mean period of 40 +/- 47 months and 8 were treated with continuous ambulatory peritoneal dialysis (CAPD) for 20 +/- 15 months. Patient survival rate at 1 and 5 years was 68% and 30% respectively. There was no difference in survival rate between patients treated with HD and those treated with CAPD, while patients younger than 45 had a better 5-year survival rate. Twenty four (60%) patients achieved a satisfactory rehabilitation with dialysis. At the last follow-up, 15 patients (14 on HD, 1 on CAPD) were alive 61 +/- 58 months after starting dialysis. Twenty-eight patients died after 30 +/- 20 months. The main causes of death were: cardiovascular accident (11), stroke (3), sepsis (5) and cachexia (5). The most important extra-renal complications of amyloidosis were related to cardiovascular involvement (heart failures, arrhythmias, hypotension) and gastrointestinal involvement (malabsorption). Intra-dialytic hypotension in patients on HD and peritonitis in patients on CAPD were the main problems related to dialytic procedure. his study confirms that life expectancy and the quality of life of dialysis patients with systemic amyloidosis are poorer than those of general dialysis population.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular requirements of the active sites of the cholinergic receptors. XVIII-Correlation between activity and double bond position among cyclopentene derivatives

Some cyclopentene derivatives lacking the oxygenated functions have been synthesized and tested as cholinergic compounds. Their good muscarinic potency seems to confirm that such compounds interact with a receptor area which is not coincident with that recognized by other cholinergic agents such as muscarine and deoxamuscarine.

Molecular requirements of the active sites of the cholinergic receptors. XIII - Stereospecific synthesis of 3c-methyl-2t-hydroxy-lr-dimethyl-aminomethylcyclopentane methiodide and its dehydroderivative

A stereospecific synthesis of 3c-methyl-2t-hydroxy-1r-dimethylaminomethylcyclopentane methiodide (III), which allows better yields, avoiding time-consuming column chromatography and the synthesis of its dehydroderivative (VIII) are described. This last compound, like isomer (VII) (2), shows a good cholinergic activity which, compared with that of the corresponding hydroxycompounds, further supports the dualistic hypothesis of Triggle (8) on the active sites of cholinergic receptors.