George E. Sandusky

FGF-21 as a novel metabolic regulator

Diabetes mellitus is a major health concern, affecting more than 5% of the population. Here we describe a potential novel therapeutic agent for this disease, FGF-21, which was discovered to be a potent regulator of glucose uptake in mouse 3T3-L1 and primary human adipocytes. FGF-21-transgenic mice were viable and resistant to diet-induced obesity. Therapeutic administration of FGF-21 reduced plasma glucose and triglycerides to near normal levels in both ob/ob and db/db mice. These effects persisted for at least 24 hours following the cessation of FGF-21 administration. Importantly, FGF-21 did not induce mitogenicity, hypoglycemia, or weight gain at any dose tested in diabetic or healthy animals or when overexpressed in transgenic mice. Thus, we conclude that FGF-21, which we have identified as a novel metabolic factor, exhibits the therapeutic characteristics necessary for an effective treatment of diabetes.

Increased Protein Kinase C Activity and Expression of Ca2+-Sensitive Isoforms in the Failing Human Heart

BACKGROUND Increased expression of Ca2+-sensitive protein kinase C (PKC) isoforms may be important markers of heart failure. Our aim was to determine the relative expression of PKC-beta1, -beta2, and -alpha in failed and nonfailed myocardium. METHODS AND RESULTS Explanted hearts of patients in whom dilated cardiomyopathy or ischemic cardiomyopathy was diagnosed were examined for PKC isoform content by Western blot, immunohistochemistry, enzymatic activity, and in situ hybridization and compared with nonfailed left ventricle. Quantitative immunoblotting revealed significant increases of >40% in PKC-beta1 (P<0.05) and -beta2 (P<0.04) membrane expression in failed hearts compared with nonfailed; PKC-alpha expression was significantly elevated by 70% in membrane fractions (P<0.03). PKC-epsilon expression was not significantly changed. In failed left ventricle, PKC-beta1 and -beta2 immunostaining was intense throughout myocytes, compared with slight, scattered staining in nonfailed myocytes. PKC-alpha immunostaining was also more evident in cardiomyocytes from failed hearts with staining primarily localized to intercalated disks. In situ hybridization revealed increased PKC-beta1 and -beta2 mRNA expression in cardiomyocytes of failed heart tissue. PKC activity was significantly increased in membrane fractions from failed hearts compared with nonfailed (1021+/-189 versus 261+/-89 pmol. mg-1. min-1, P<0.01). LY333531, a selective PKC-beta inhibitor, significantly decreased PKC activity in membrane fractions from failed hearts by 209 pmol. min-1. mg-1 (versus 42.5 pmol. min-1. mg-1 in nonfailed, P<0.04), indicating a greater contribution of PKC-beta to total PKC activity in failed hearts. CONCLUSIONS In failed human heart, PKC-beta1 and -beta2 expression and contribution to total PKC activity are significantly increased. This may signal a role for Ca2+-sensitive PKC isoforms in cardiac mechanisms involved in heart failure.

Increased AKT Activity Contributes to Prostate Cancer Progression by Dramatically Accelerating Prostate Tumor Growth and Diminishing p27Kip1 Expression

The PTEN tumor suppressor gene is frequently inactivated in human prostate cancers, particularly in more advanced cancers, suggesting that the AKT/protein kinase B (PKB) kinase, which is negatively regulated by PTEN, may be involved in human prostate cancer progression. We now show that AKT activation and activity are markedly increased in androgen-independent, prostate-specific antigen-positive prostate cancer cells (LNAI cells) established from xenograft tumors of the androgen-dependent LNCaP cell line. These LNAI cells show increased expression of integrin-linked kinase, which is putatively responsible for AKT activation/Ser-473 phosphorylation, as well as for increased phosphorylation of the AKT target protein, BAD. Furthermore, expression of the p27Kip1 cell cycle regulator was diminished in LNAI cells, consistent with the notion that AKT directly inhibits AFX/Forkhead-mediated transcription of p27Kip1. To assess directly the impact of increased AKT activity on prostate cancer progression, an activated hAKT1 mutant was overexpressed in LNCaP cells, resulting in a 6-fold increase in xenograft tumor growth. Like LNAI cells, these transfectants showed dramatically reduced p27Kip1 expression. Together, these data implicate increased AKT activity in prostate tumor progression and androgen independence and suggest that diminished p27Kip1expression, which has been repeatedly associated with prostate cancer progression, may be a consequence of increased AKT activity.

Fibroblast Growth Factor-21 Improves Pancreatic β-Cell Function and Survival by Activation of Extracellular Signal–Regulated Kinase 1/2 and Akt Signaling Pathways

Fibroblast growth factor-21 (FGF-21) is a recently discovered metabolic regulator. Here, we investigated the effects of FGF-21 in the pancreatic β-cell. In rat islets and INS-1E cells, FGF-21 activated extracellular signal–regulated kinase 1/2 and Akt signaling pathways. In islets isolated from healthy rats, FGF-21 increased insulin mRNA and protein levels but did not potentiate glucose-induced insulin secretion. Islets and INS-1E cells treated with FGF-21 were partially protected from glucolipotoxicity and cytokine-induced apoptosis. In islets isolated from diabetic rodents, FGF-21 treatment increased islet insulin content and glucose-induced insulin secretion. Short-term treatment of normal or db/db mice with FGF-21 lowered plasma levels of insulin and improved glucose clearance compared with vehicle after oral glucose tolerance testing. Constant infusion of FGF-21 for 8 weeks in db/db mice nearly normalized fed blood glucose levels and increased plasma insulin levels. Immunohistochemistry of pancreata from db/db mice showed a substantial increase in the intensity of insulin staining in islets from FGF-21–treated animals as well as a higher number of islets per pancreas section and of insulin-positive cells per islet compared with control. No effect of FGF-21 was observed on islet cell proliferation. In conclusion, preservation of β-cell function and survival by FGF-21 may contribute to the beneficial effects of this protein on glucose homeostasis observed in diabetic animals.

Small Intestinal Submucosa as a Vascular Graft: A Review

Continuing investigations of vascular graft materials suggest that unacceptable graft complications continue and that the ideal graft material has not yet been found. We have developed and tested a biologic vascular graft material, small intestine submucosa (SIS), in normal dogs. This material, when used as an autograft, allograft, or xenograft has demonstrated biocompatibility and high patency rates in aorta, carotid and femoral arteries, and superior vena cava locations. The grafts are completely endothelialized at 28 days post-implantation. At 90 days, the grafts are histologically similar to normal arteries and veins and contain a smooth muscle media and a dense fibrous connective tissue adventitia. Follow-up periods of up to 5 years found no evidence of infection, intimal hyperplasia, or aneurysmal dilation. One infection-challenge study suggested that SIS may be infection resistant, possibly because of early capillary penetration of the SIS (2 to 4 days after implantation) and delivery of body defenses to the local site. We conclude that SIS is a suitable blood interface material and is worthy of continued investigation. It may serve as a structural framework for the application of tissue engineering technologies in the development of the elusive ideal vascular graft material.

Bone neoplasms in F344 rats given teriparatide [rhPTH(1-34)] are dependent on duration of treatment and dose.

A long-term study was conducted in female F344 rats to determine the relative importance of dose, treatment duration, and age at initiation of treatment on the incidence of teriparatide [rhPTH[1-34)]-induced bone proliferative lesions. Treatment groups consisted of different combinations of dose (0, 5, or 30 μg/kg/d), treatment duration (6, 20, or 24 months) and age at initiation of treatment (2 or 6 months of age). The primary endpoints were the incidence of bone neoplasms and effects on bone mass and structure as evaluated by quantitative computed tomography and histomorphometery. Significant increases in the incidence of bone tumors (osteoma, osteoblastoma, and osteosarcoma) occurred in rats treated with 30 μg/kg for 20 or 24 months. No neoplasms were found when the 5 μg/kg treatment was initiated at 6 months of age and continued for either 6 or 20 months (up to 70% of life span). This treatment regimen defined a “no-effect” dose for neoplasm formation that nevertheless resulted in substantial increases in bone mass. These results demonstrate that treatment duration and administered dose are the most important factors in the teriparatide-induced bone tumors in rats.

Vascular Injury, Repair, and Restenosis After Percutaneous Transluminal Angioplasty in the Atherosclerotic Rabbit

BACKGROUND Several nonatherosclerotic animal models of restenosis exist and are used for the evaluation of the vascular response to angioplasty-induced injury. However, few studies have evaluated the response of an atherosclerotic vessel to angioplasty. The present study examined the radiographic, histological, immunohistochemical, and morphometric responses over time of atherosclerotic rabbit femoral arteries after percutaneous transluminal angioplasty (PTA). METHODS AND RESULTS Rabbits (n = 94) underwent arterial dissection and were fed a hypercholesterolemic diet for 3 weeks, and then PTA was performed. Arteries were obtained before PTA and 1, 3, 5, 7, 14, and 28 days after PTA. PTA caused radial stretching of the artery, medial compression, intramural hemorrhage, injury to normal arterial segments, and dissection within the intima and media. Thrombus filled and cellular accumulation repaired the dissection. Peak smooth muscle cell and macrophage DNA synthesis was noted at 3 to 5 days after angioplasty, generally at the dissection but also in normal sections of the artery. Adventitial injury and subsequent adventitial cellular proliferation and collagen production were observed. A rapid decrease in the radiographic minimal luminal diameter was noted at 3 days, resulting from vascular recoil or thrombus filling the dissection. At 7 to 14 days, only 24% to 33% of the luminal loss was accounted for by an increase in the intimal area, and 22% to 28% of the intima was neointima. CONCLUSIONS Restenosis in an atherosclerotic artery results from a variable combination of intimal proliferation, vascular remodeling/wound contraction, and recoil of the normal section of the artery. The variability of an atherosclerotic artery to PTA injury results from variable dissection, thrombus formation, and cellular response to injury as well as variable scar contraction and elastic recoil.

Small intestinal submucosa as a superior vena cava graft in the dog.

Autogenous spiral vein grafts and ePTFE have been used for reconstruction of the superior vena cava with moderate success. We tested autogenous small intestine submucosa as a superior vena cava interpositional graft in nine dogs. All dogs received aspirin and warfarin sodium for the first 8 weeks after surgery. Graft patency was evaluated by serial venography. One dog died from excessive anticoagulation. Eight dogs were sacrificed at periodic intervals until 72 weeks after surgery. Patent grafts had no evidence of thrombosis, aneurysm, or stenosis. The grafts consisted of dense, organized collagenous connective tissue with a complete endothelial cell layer on the luminal surface. Two dogs are alive at 28 and 34 months after surgery. Graft patency was 89% (eight of nine grafts). We conclude that autogenous small intestine submucosa can be used as a superior vena cava graft in the dog and is worthy of further investigations.

Antisense Inhibition of Survivin Expression as a Cancer Therapeutic

Survivin, a family member of the inhibitor of apoptosis proteins that is expressed during mitosis in a cell cycle–dependent manner and localized to different components of the mitotic apparatus, plays an important role in both cell division and inhibition of apoptosis. Survivin is expressed in a vast majority of human cancers, but not in normal adult tissues. Survivin expression is often correlated with poor prognosis in a wide variety of cancer patients. These features make survivin an attractive target against which cancer therapeutics could be developed. We have identified a survivin antisense oligonucleotide (ASO) that potently downregulated survivin expression in human cancer cells derived from lung, colon, pancreas, liver, breast, prostate, ovary, cervix, skin, and brain as measured by quantitative RT-PCR and immunoblotting analysis. Specific inhibition of survivin expression in multiple cancer cell lines by this ASO (LY2181308) induced caspase-3–dependent apoptosis, cell cycle arrest in the G2‐M phase, and multinucleated cells. We also showed that inhibition of survivin expression by LY2181308 sensitized tumor cells to chemotherapeutic-induced apoptosis. Most importantly, in an in vivo human xenograft tumor model, LY2181308 produced significant antitumor activity as compared with saline or its sequence-specific control oligonucleotide and sensitized to gemcitabine, paclitaxel, and docetaxel. Furthermore, we showed that this antitumor activity was associated with significant inhibition of survivin expression in these xenograft tumors. On the basis of these, LY2181308 is being evaluated in a clinical setting (Phase II) in combination with docetaxel for the treatment of prostate cancer. Mol Cancer Ther; 10(2); 221–32. ©2011 AACR.

Local delivery of biodegradable microparticles containing colchicine or a colchicine analogue: Effects on restenosis and implications for catheter-based drug delivery

OBJECTIVES This study sought to evaluate the delivery efficiency, intramural retention and antirestenotic efficacy of soluble colchicine or colchicine analogue delivered into the arterial wall after angioplasty as well as the efficacy of these medications after prolonged local release from biodegradable microparticles. BACKGROUND Local delivery of pharmacologic agents is a potential treatment for restenosis. However, the delivery efficiency of the technique and the choice of agent to modulate cellular proliferation are unknown. It was hypothesized that restenosis would be unaffected by colchicine or a hydrophobic colchicine analogue with short intramural retention, whereas it would be reduced after prolonged local release. METHODS Rabbit atherosclerotic femoral arteries underwent angioplasty followed by local delivery. Delivery efficiency and intramural retention of 3H-colchicine were evaluated. The effect of agents in soluble formulation or released from microparticles on angiographic and morphometric restenosis was evaluated at 2 weeks and compared with that in the control groups (angioplasty only and local infusion of carrier solution). RESULTS Delivery of efficiency was 0.01% and intramural retention < 24 h. Neither soluble colchicine formulation reduced restenosis. Microparticles releasing the colchicine analogue reduced restenosis compared with control and colchicine microparticles but not angioplasty alone (p = 0.002). Delivery outside the artery was observed, and the long-term release of both colchicine resulted in toxicity to the adjacent musculature. CONCLUSIONS Colchicine or the colchicine analogue did not reduce restenosis, although the long-term local release of the colchicine analogue reduced neointimal proliferation resulting from local delivery. Local delivery of cytotoxic agents with insufficient vascular specificity may be limited by toxicity to adjacent tissues resulting from a larger than expected delivery area and prolonged agent retention.