Nawal M. Al-Rasheed

Publications (5)19.21 Total impact

• Article: C-peptide signals via Galpha i to protect against TNF-alpha-mediated apoptosis of opossum kidney proximal tubular cells.

  Nawal M Al-Rasheed, Gary B Willars, Nigel J Brunskill
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  ABSTRACT: Cell loss by apoptosis occurs in renal injury such as diabetic nephropathy. TNF-alpha is a cytokine that induces apoptosis and has been implicated in the pathogenesis of diabetic nephropathy. The aim was to investigate whether C-peptide or insulin could modulate TNF-alpha-mediated cell death in opossum kidney proximal tubular cells and to examine the mechanism(s) of any effects observed. C-peptide and insulin protect against TNF-alpha-induced proximal tubular cell toxicity and apoptosis. Cell viability was analyzed by methylthiazoletetrazolium assay; cell viability was reduced to 60.8 +/- 2.7% of control after stimulation with 300 ng/ml TNF-alpha. Compromised cell viability was reversed by pretreatment with 5 nM C-peptide or 100 nM insulin. TNF-alpha-induced apoptosis was detected by DNA nick-end labeling and by measuring histone associated DNA fragments using ELISA. By ELISA assay, 300 ng/ml TNF-alpha increased apoptosis by 145.8 +/- 4.9% compared with controls, whereas 5 nM C-peptide and 100 nM insulin reduced apoptosis to 81.6 +/- 4.8 and 77.4 +/- 3.1% of control, respectively. The protective effects of C-peptide and insulin were associated with activation of NF-kappaB. Activation of NF-kappaB by C-peptide was pertussis toxin sensitive and dependent on activation of Galpha(i). Phosphatidylinositol 3-kinase but not extracellular signal regulated mitogen-activated protein kinase mediated C-peptide and insulin activation of NF-kappaB. The cytoprotective effects of both C-peptide and insulin were related to increased expression of TNF receptor-associated factor 2, the product of an NF-kappaB-dependent survival gene. These data suggest that C-peptide and/or insulin activation of NF-kappaB-regulated survival genes protects against TNF-alpha-induced renal tubular injury in diabetes. The data further support the concept of C-peptide as a peptide hormone in its own right and suggest a potential therapeutic role for C-peptide.
  Journal of the American Society of Nephrology 05/2006; 17(4):986-95. · 9.66 Impact Factor
• Article: Ligand-independent activation of peroxisome proliferator-activated receptor-gamma by insulin and C-peptide in kidney proximal tubular cells: dependent on phosphatidylinositol 3-kinase activity.

  Nawal M Al-Rasheed, Ravinder S Chana, Richard J Baines, Gary B Willars, Nigel J Brunskill
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  ABSTRACT: Peroxisome proliferator-activated receptor gamma (PPARgamma) has key roles in the regulation of adipogenesis, inflammation, and lipid and glucose metabolism. C-peptide is believed to be inert and without appreciable biological functions. Recent studies suggest that C-peptide possesses multiple functions. The present study investigated the effects of insulin and C-peptide on PPARgamma transcriptional activity in opossum kidney proximal tubular cells. Both insulin and C-peptide induced a concentration-dependent stimulation of PPARgamma transcriptional activity. Both agents substantially augmented thiazolidinedione-stimulated PPARgamma transcriptional activity. Neither insulin nor C-peptide had any effect on the expression levels of PPARgamma. GW9662, a PPARgamma antagonist, blocked PPARgamma activation by thiazolidinediones but had no effect on either insulin- or C-peptide-stimulated PPARgamma transcriptional activity. Co-transfection of opossum kidney cells with dominant negative mitogen-activated protein kinase kinase significantly depressed basal PPARgamma transcriptional activity but had no effect on that induced by either insulin or C-peptide. Both insulin- and C-peptide-stimulated PPARgamma transcriptional activity were attenuated by wortmannin and by expression of a dominant negative phosphatidylinositol (PI) 3-kinase p85 regulatory subunit. In addition PI 3-kinase-dependent phosphorylation of PPARgamma was observed after stimulation by C-peptide or insulin. C-peptide effects but not insulin on PPARgamma transcriptional activity were abolished by pertussis toxin pretreatment. Finally both C-peptide and insulin positively control the expression of the PPARgamma-regulated CD36 scavenger receptor in human THP-1 monocytes. We concluded that insulin and C-peptide can stimulate PPARgamma activity in a ligand-independent fashion and that this effect is mediated by PI 3-kinase. These results support a new and potentially important physiological role for C-peptide in regulation of PPARgamma-related cell functions.
  Journal of Biological Chemistry 12/2004; 279(48):49747-54. · 4.77 Impact Factor
• Article: Ligand-independent Activation of Peroxisome Proliferator-activated Receptor-γ by Insulin and C-peptide in Kidney Proximal Tubular Cells

  Nawal M. Al-Rasheed, Ravinder S. Chana, Richard J. Baines, Gary B. Willars, Nigel J. Brunskill
  [show abstract] [hide abstract]
  ABSTRACT: Peroxisome proliferator-activated receptor γ (PPARγ) has key roles in the regulation of adipogenesis, inflammation, and lipid and glucose metabolism. C-peptide is believed to be inert and without appreciable biological functions. Recent studies suggest that C-peptide possesses multiple functions. The present study investigated the effects of insulin and C-peptide on PPARγ transcriptional activity in opossum kidney proximal tubular cells. Both insulin and C-peptide induced a concentration-dependent stimulation of PPARγ transcriptional activity. Both agents substantially augmented thiazolidinedione-stimulated PPARγ transcriptional activity. Neither insulin nor C-peptide had any effect on the expression levels of PPARγ. GW9662, a PPARγ antagonist, blocked PPARγ activation by thiazolidinediones but had no effect on either insulin- or C-peptide-stimulated PPARγ transcriptional activity. Co-transfection of opossum kidney cells with dominant negative mitogen-activated protein kinase kinase significantly depressed basal PPARγ transcriptional activity but had no effect on that induced by either insulin or C-peptide. Both insulin- and C-peptide-stimulated PPARγ transcriptional activity were attenuated by wortmannin and by expression of a dominant negative phosphatidylinositol (PI) 3-kinase p85 regulatory subunit. In addition PI 3-kinase-dependent phosphorylation of PPARγ was observed after stimulation by C-peptide or insulin. C-peptide effects but not insulin on PPARγ transcriptional activity were abolished by pertussis toxin pretreatment. Finally both C-peptide and insulin positively control the expression of the PPARγ-regulated CD36 scavenger receptor in human THP-1 monocytes. We concluded that insulin and C-peptide can stimulate PPARγ activity in a ligand-independent fashion and that this effect is mediated by PI 3-kinase. These results support a new and potentially important physiological role for C-peptide in regulation of PPARγ-related cell functions.
  Journal of Biological Chemistry 11/2004; 279(48):49747-49754. · 4.77 Impact Factor
• Article: C-peptide reverses TGF-β1-induced changes in renal proximal tubular cells: implications for treatment of diabetic nephropathy

  Claire E Hills, Nawal M. Al-Rasheed, Nouf Al-Rasheed, Gary B Willars, Nigel J Brunskill
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  ABSTRACT: This paper was published as American Journal of Physiology - Renal Physiology, 2009, 296 (3), pp. F614-F621. It is available from http://ajprenal.physiology.org/cgi/content/abstract/296/3/F614. Doi: 10.1152/ajprenal.90500.2008 Metadata only entry The crucial pathology underlying progressive chronic kidney disease in diabetes is tubulointerstitial fibrosis. Central to this process is epithelial-mesenchymal transformation (EMT) of proximal tubular epithelial cells driven by maladaptive transforming growth factor-β1 (TGF-β1) signaling. Novel signaling roles for C-peptide have recently been discovered with evidence emerging that C-peptide may mitigate microvascular complications of diabetes. We studied the potential for C-peptide to interrupt injurious TGF-β1 signaling pathways and thus block development of EMT in HK2 human kidney proximal tubular cells. Cells were incubated with TGF-β1 either alone or with C-peptide in low or high glucose. Changes in cell morphology, TGF-β1 receptor expression, vimentin, E-cadherin, and phosphorylated Smads were assessed. Luciferase reporters were used to assess Smad activity. The cytoskeleton was visualized by TRITC-phalloidin staining. The typical TGF-β1-stimulated, EMT-associated morphological alterations of proximal tubular cells, including increased vimentin expression, decreased E-cadherin expression, and cytoskeletal rearrangements, were prevented by C-peptide treatment. C-peptide also blocked TGF-β1-induced upregulation of expression of both type I and type II TGF-β1 receptors and attenuated TGF-β1-mediated Smad phosphorylation and Smad transcriptional activity. These effects of C-peptide were inhibited by pertussis toxin. The results demonstrate that C-peptide almost completely reversed the morphological changes in PT cells induced by TGF-β1 and suggest a role or C-peptide as a renoprotective agent in diabetic nephropathy.
• Article: C-Peptide signals via Gαi to protect against TNF-α-mediated apoptosis of opossum kidney proximal tubular cells.

  Nawal M. Al-Rasheed, Gary B Willars, Nigel J Brunskill
  [show abstract] [hide abstract]
  ABSTRACT: This paper was published as Journal of American Society of Nephrology, 2006, 17, pp.986-995. It is available from http://jasn.asnjournals.org/cgi/content/abstract/17/4/986. Doi: 10.1681/ASN.2005080797 Cell loss by apoptosis occurs in renal injury such as diabetic nephropathy. TNF- is a cytokine that induces apoptosis and has been implicated in the pathogenesis of diabetic nephropathy. The aim was to investigate whether C-peptide or insulin could modulate TNF-–mediated cell death in opossum kidney proximal tubular cells and to examine the mechanism(s) of any effects observed. C-peptide and insulin protect against TNF-–induced proximal tubular cell toxicity and apoptosis. Cell viability was analyzed by methylthiazoletetrazolium assay; cell viability was reduced to 60.8 ± 2.7% of control after stimulation with 300 ng/ml TNF-. Compromised cell viability was reversed by pretreatment with 5 nM C-peptide or 100 nM insulin. TNF-–induced apoptosis was detected by DNA nick-end labeling and by measuring histone associated DNA fragments using ELISA. By ELISA assay, 300 ng/ml TNF- increased apoptosis by 145.8 ± 4.9% compared with controls, whereas 5 nM C-peptide and 100 nM insulin reduced apoptosis to 81.6 ± 4.8 and 77.4 ± 3.1% of control, respectively. The protective effects of C-peptide and insulin were associated with activation of NF-B. Activation of NF-B by C-peptide was pertussis toxin sensitive and dependent on activation of Gi. Phosphatidylinositol 3-kinase but not extracellular signal regulated mitogen-activated protein kinase mediated C-peptide and insulin activation of NF-B. The cytoprotective effects of both C-peptide and insulin were related to increased expression of TNF receptor–associated factor 2, the product of an NF-B–dependent survival gene. These data suggest that C-peptide and/or insulin activation of NF-B–regulated survival genes protects against TNF-–induced renal tubular injury in diabetes. The data further support the concept of C-peptide as a peptide hormone in its own right and suggest a potential therapeutic role for C-peptide.