Urinary MicroRNA Profiling in the Nephropathy of Type 1 Diabetes

Background: Patients with Type 1 Diabetes (T1D) are particularly vulnerable to development of Diabetic nephropathy (DN) leading to End Stage Renal Disease. Hence a better understanding of the factors affecting kidney disease progression in T1D is urgently needed. In recent years microRNAs have emerged as important post-transcriptional regulators of gene expression in many different health conditions. We hypothesized that urinary microRNA profile of patients will differ in the different stages of diabetic renal disease. Methods and Findings: We studied urine microRNA profiles with qPCR in 40 T1D with >20 year follow up 10 who never developed renal disease (N) matched against 10 patients who went on to develop overt nephropathy (DN), 10 patients with intermittent microalbuminuria (IMA) matched against 10 patients with persistent (PMA) microalbuminuria. A Bayesian procedure was used to normalize and convert raw signals to expression ratios. We applied formal statistical techniques to translate fold changes to profiles of microRNA targets which were then used to make inferences about biological pathways in the Gene Ontology and REACTOME structured vocabularies. A total of 27 microRNAs were found to be present at significantly different levels in different stages of untreated nephropathy. These microRNAs mapped to overlapping pathways pertaining to growth factor signaling and renal fibrosis known to be targeted in diabetic kidney disease. Conclusions: Urinary microRNA profiles differ across the different stages of diabetic nephropathy. Previous work using experimental, clinical chemistry or biopsy samples has demonstrated differential expression of many of these microRNAs in a variety of chronic renal conditions and diabetes. Combining expression ratios of microRNAs with formal inferences about their predicted mRNA targets and associated biological pathways may yield useful markers for early diagnosis and risk stratification of DN in T1D by inferring the alteration of renal molecular processes. © 2013 Argyropoulos et al

Alteration of AKT Activity Increases Chemotherapeutic Drug and Hormonal Resistance in Breast Cancer yet Confers an Achilles Heel by Sensitization to Targeted Therapy

The PI3K/PTEN/Akt/mTOR pathway plays critical roles in the regulation of cell growth. The effects of this pathway on drug resistance and cellular senescence of breast cancer cells has been a focus of our laboratory. Introduction of activated Akt or mutant PTEN constructs which lack lipid phosphatase [PTEN(G129E)] or lipid and protein phosphatase [PTEN(C124S)] activity increased the resistance of the cells to the chemotherapeutic drug doxorubicin, and the hormonal drug tamoxifen. Activated Akt and PTEN genes also inhibited the induction of senescence after doxorubicin treatment; a phenomenon associated with unrestrained proliferation and tumorigenesis. Interference with the lipid phosphatase domain of PTEN was sufficient to activate Akt/mTOR/p70S6K as MCF-7 cells transfected with the mutant PTEN gene lacking the lipid phosphatase activity [PTEN(G129E)] displayed elevated levels of activated Akt and p70S6K compared to empty vector transfected cells. Cells transfected with mutant PTEN or Akt constructs were hypersensitive to mTOR inhibitors when compared with the parental or empty vector transfected cells. Akt-transfected cells were cultured for over two months in tamoxifen from which tamoxifen and doxorubicin resistant cells were isolated that were >10-fold more resistant to tamoxifen and doxorubicin than the original Akt-transfected cells. These cells had a decreased induction of both activated p53 and total p21Cip1 upon doxorubicin treatment. Furthermore, these cells had an increased inactivation of GSK-3β and decreased expression of the estrogen receptor-α. In these drug resistant cells, there was an increased activation of ERK which is associated with proliferation. These drug resistant cells were hypersensitive to mTOR inhibitors and also sensitive to MEK inhibitors, indicating that the enhanced p70S6K and ERK expression was relevant to their drug and hormonal resistance. Given that Akt is overexpressed in greater than 50% of breast cancers, our results point to potential therapeutic targets, mTOR and MEK. These studies indicate that activation of the Akt kinase or disruption of the normal activity of the PTEN phosphatase can have dramatic effects on activity of p70S6K and other downstream substrates and thereby altering the therapeutic sensitivity of breast cancer cells. The effects of doxorubicin and tamoxifen on induction of the Raf/MEK/ERK and PI3K/Akt survival pathways were examined in unmodified MCF-7 breast cells. Doxorubicin was a potent inducer of activated ERK and to a lesser extent Akt. Tamoxifen also induced ERK. Thus a consequence of doxorubicin and tamoxifen therapy of breast cancer is the induction of a pro-survival pathway which may contribute to the development of drug resistance. Unmodified MCF-7 cells were also sensitive to MEK and mTOR inhibitors which synergized with both tamoxifen and doxorubicin to induce death. In summary, our results point to the key interactions between the PI3K/PTEN/Akt/mTOR and Raf/ MEK/ERK pathways in regulating chemotherapeutic drug resistance/sensitivity in breast cancer and indicate that targeting these pathways may prevent drug and hormonal resistance. Orignally published Advances in Enzyme Regulation, Vol. 48, No. 1, 2008

Dysfunction of Small-Conductance Ca2+-Activated Potassium (SK) Channels Drives Amygdala Hyperexcitability and Neuropathic Pain Behaviors: Involvement of Epigenetic Mechanisms

Neuroplasticity in the amygdala and its central nucleus (CeA) is linked to pain modulation and pain behaviors, but cellular mechanisms are not well understood. Here, we addressed the role of small-conductance Ca2+-activated potassium (SK) channels in pain-related amygdala plasticity. The facilitatory effects of the intra-CeA application of an SK channel blocker (apamin) on the pain behaviors of control rats were lost in a neuropathic pain model, whereas an SK channel activator (NS309) inhibited pain behaviors in neuropathic rats but not in sham controls, suggesting the loss of the inhibitory behavioral effects of amygdala SK channels. Brain slice electrophysiology found hyperexcitability of CeA neurons in the neuropathic pain condition due to the loss of SK channel-mediated medium afterhyperpolarization (mAHP), which was accompanied by decreased SK2 channel protein and mRNA expression, consistent with a pretranscriptional mechanisms. The underlying mechanisms involved the epigenetic silencing of the SK2 gene due to the increased DNA methylation of the CpG island of the SK2 promoter region and the change in methylated CpG sites in the CeA in neuropathic pain. This study identified the epigenetic dysregulation of SK channels in the amygdala (CeA) as a novel mechanism of neuropathic pain-related plasticity and behavior that could be targeted to control abnormally enhanced amygdala activity and chronic neuropathic pain

Functional analysis of the protein phosphatase activity of PTEN

In vitro, the tumour suppressor PTEN (phosphatase and tensin homologue deleted on chromosome 10) displays intrinsic phosphatase activity towards both protein and lipid substrates. In vivo, the lipid phosphatase activity of PTEN, through which it dephosphorylates the 3 position in the inositol sugar of phosphatidylinositol derivatives, is important for its tumour suppressor function; however, the significance of its protein phosphatase activity remains unclear. Using two-photon laser-scanning microscopy and biolistic gene delivery of GFP (green fluorescent protein)-tagged constructs into organotypic hippocampal slice cultures, we have developed an assay of PTEN function in living tissue. Using this bioassay, we have demonstrated that overexpression of wild-type PTEN led to a decrease in spine density in neurons. Furthermore, it was the protein phosphatase activity, but not the lipid phosphatase activity, of PTEN that was essential for this effect. The ability of PTEN to decrease neuronal spine density depended upon the phosphorylation status of serine and threonine residues in its C-terminal segment and the integrity of the C-terminal PDZ-binding motif. The present study reveals a new aspect of the function of this important tumour suppressor and suggest that, in addition to dephosphorylating the 3 position in phosphatidylinositol phospholipids, the critical protein substrate of PTEN may be PTEN itself

Type 1 diabetes mellitus induces structural changes and molecular remodelling in the rat kidney

There is much evidence that diabetes mellitus (DM) –induced hyperglycemia (HG) is responsible for kidney failure or nephropathy leading to cardiovascular complications. Cellular and molecular mechanism(s) whereby DM can damage the kidney is still not fully understood. This study investigated the effect of streptozotocin (STZ)-induced diabetes (T1DM) on the structure and associated molecular alterations of the isolated rat left kidney following 2 and 4 months of the disorder compared to the respective age-matched controls. The results revealed hypertrophy and general disorganized architecture of the kidney characterized by expansion in glomerular borders, tubular atrophy and increased vacuolization of renal tubular epithelial cells in the diabetic groups compared to controls. Electron microscopic analysis revealed ultrastructural alterations in the left kidney highlighted by an increase in glomerular basement membrane width. In addition, increased caspase-3 immuno-reactivity was observed in the kidney of T1DM animals compared to age-matched controls. These structural changes were associated with elevated extracellular matrix (ECM) deposition and consequently, altered gene expression profile of ECM key components, together with elevated levels of key mediators (MMP9, integrin 5α, TIMP4, CTGF, vimentin) and reduced expressions of Cx43 and MMP2 of the ECM. Marked hypertrophy of the kidney was highlighted by increased atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) gene expression. These changes also correlated with increased TGFβ1 activity, gene expression in the left kidney and elevated active TGFβ1 in plasma of T1DM rats compared to control. The results clearly demonstrated that TIDM could elicit severe structural changes and alteration in biochemical markers (remodeling) in the kidney leading to diabetic nephropathy (DN)

Mesangial cell hypertrophy by high glucose is mediated by downregulation of the tumor suppressor PTEN

Diabetic nephropathy is characterized early in its course by glomerular hypertrophy and, importantly, mesangial hypertrophy, which correlate with eventual glomerulosclerosis. The mechanism of hypertrophy, however, is not known. Gene disruption of the tumor suppressor PTEN, a negative regulator of the phosphatidylinositol 3-kinase/Akt pathway, in fruit flies and mice demonstrated its role in size control in a cell-specific manner. Here, we investigated the mechanism of mesangial hypertrophy in response to high extracellular glucose. We link early renal hypertrophy with significant reduction in PTEN expression in the streptozotocin-induced diabetic kidney cortex and glomeruli, concomitant with activation of Akt. Similarly, exposure of mesangial cells to high concentrations of glucose also decreased PTEN expression and its phosphatase activity, resulting in increased Akt activity. Expression of PTEN inhibited high-glucose\u96induced mesangial cell hypertrophy, and expression of dominant-negative PTEN was sufficient to induce hypertrophy. In diabetic nephropathy, the hypertrophic effect of hyperglycemia is thought to be mediated by transforming growth factor- f (TGF- f). TGF- f significantly reduced PTEN expression in mesangial cells, with a reduction in its phosphatase activity and an increase in Akt activation. PTEN and dominant-negative Akt attenuated TGF- f\u96induced hypertrophy of mesangial cells. Finally, we show that inhibition of TGF- f signal transduction blocks the effect of high glucose on PTEN downregulation. These data identify a novel mechanism placing PTEN as a key regulator of diabetic mesangial hypertrophy involving TGF- f signaling

Evaluation of SARS-CoV-2 Serological Testing in Patients with Multiple Myeloma and Other Hematologic Malignancies on Monoclonal Antibody Therapies

Background: Patients with hematological malignancies (HM), including multiple myeloma (MM), frequently suffer from immune deficiency-associated infectious complications because of both the disease and the treatment. Alarming results from China and the UK confirm the vulnerability of HM patients to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-driven coronavirus disease 2019 (COVID-19). Given that the immunoassay interference from the endogenous monoclonal immunoglobulin (M paraprotein) and treatment antibodies continually challenges the MM management, it is critical to evaluate the SARS-CoV-2 serology tests for suspected interference/cross-reactivity. Methods: We compared the degree of interference in three SARS-CoV-2 serology assay platforms in HM patients with and without COVID-19 and on various therapeutic monoclonal antibody (t-mAb) treatments. Further, we confirmed the cross-reactivity in pooled samples from normal and COVID-19 + samples spiked with respective antibodies in vitro. Results: None of the 93 HM patient samples with or without t-MAbs showed cross-reactivity on any of the three serology platforms tested. Conclusions: The tested three serologic assays for SARS-CoV-2 are specific and do not have cross-reactivity with M-components or t-MAbs indicating that they can be used safely in oncology practice and in research exploring the immunologic response to COVID-19 in patients with HM