A pilot double-blind safety and feasibility randomized controlled trial of high-dose intravenous zinc in hospitalized COVID-19 patients.

Zinc inhibits replication of the SARS-CoV virus. We aimed to evaluate the safety, feasibility, and biological effect of administering high-dose intravenous zinc (HDIVZn) to patients with COVID-19. We performed a Phase IIa double-blind, randomized controlled trial to compare HDIVZn to placebo in hospitalized patients with COVID-19. We administered trial treatment per day for a maximum of 7 days until either death or hospital discharge. We measured zinc concentration at baseline and during treatment and observed patients for any significant side effects. For eligible patients, we randomized and administered treatment to 33 adult participants to either HDIVZn (n = 15) or placebo (n = 18). We observed no serious adverse events throughout the study for a total of 94 HDIVZn administrations. However, three participants in the HDIVZn group reported infusion site irritation. Mean serum zinc on Day 1 in the placebo, and the HDIVZn group was 6.9 ± 1.1 and 7.7 ± 1.6 µmol/l, respectively, consistent with zinc deficiency. HDIVZn, but not placebo, increased serum zinc levels above the deficiency cutoff of 10.7 µmol/l (p < .001) on Day 6. Our study did not reach its target enrollment because stringent public health measures markedly reduced patient hospitalizations. Hospitalized COVID-19 patients demonstrated zinc deficiency. This can be corrected with HDIVZn. Such treatment appears safe, feasible, and only associated with minimal peripheral infusion site irritation. This pilot study justifies further investigation of this treatment in COVID-19 patients.

Zinc supplementation as an adjunct therapy for COVID-19: Challenges and opportunities.

An outbreak of a novel coronavirus (COVID-19 or 2019-CoV) infection has posed significant threats to international health and the economy. Patients with COVID-19 are at risk of cytokine storm, acute respiratory distress syndrome (ARDS), reduced blood oxygenation, mechanical ventilation, and a high death rate. Although recent studies have shown remdesivir and dexamethasone as treatment options, there is an urgent need to find a treatment to inhibit virus replication and to control the progression of the disease. Essential biometal zinc has generated a lot of excitement as one of the promising candidates to reduce the severity of COVID-19 infection. Several published observations outlined in the review are the reasons why there is a global enthusiasm that zinc therapy could be a possible therapeutic option. However, the biggest challenge in realising the therapeutic value of zinc is lack of optimal treatment modalities such as dose, duration of zinc supplementation and the mode of delivery. In this review, we discuss the regulatory mechanism that hinges upon the bioavailability of zinc. Finally, we propose that intravenous zinc could circumvent the confounding factors affecting the bioavailability of zinc and allow zinc to achieve its therapeutic potential. If successful, due to advantages such as lack of toxicity, low cost and ease of availability, intravenous zinc could be rapidly implemented clinically.

Metformin may offer no protective effect in men undergoing external beam radiation therapy for prostate cancer.

OBJECTIVES: To assess whether metformin reduces radio-resistance and increases survival in men undergoing external beam radiation therapy (EBRT) for prostate cancer (PCa), and to determine its effect on hypoxia inducible factor 1-α (HIF1α). PATIENTS AND METHODS: All patients treated with curative intent with EBRT for PCa at a major cancer centre between 2000 and 2007 were included in this study. The outcome measures of time to biochemical failure (BF), metastasis, PCa-specific mortality and overall survival (OS) were analysed in those taking metformin vs those not, using competing risk and Cox regression models. To determine metformin's effect on HIF1α expression and survival in vitro, PC3 cells with high basal HIF1α levels were subjected to increasing doses of metformin after H2 O2 -induced oxidative stress. RESULTS: A total of 2055 eligible cases, including 113 who were on metformin, were identified, with a median follow-up of 95.7 months. There were no differences in age, initial prostate-specific antigen level, Gleason score, T-stage, D'Amico risk class or duration of androgen deprivation therapy (ADT) between patients who were or were not on metformin. Treatment with metformin did not result in any apparent improvement in time to BF, time to metastasis detection or OS, but there was a 1.5-fold increase in PCa-specific deaths (P = 0.045) in patients on metformin and ADT when adjusted for cancer risk and comorbidities. When comparing patients on high-dose metformin (>1 g/d) with those on low-dose metformin (≤1 g), there was no difference in either time to metastases or time to BF. In vitro metformin at a high concentration of 100 µM did not reduce HIF1α expression, nor did metformin affect the PC3 cell survival when exposed to oxidative stress (H2 O2 ). CONCLUSIONS: No association was found between the use of metformin and time to metastasis detection, time to BF or OS in patients undergoing radiation therapy with or without ADT for PCa. In vitro, low therapeutic concentrations of metformin had no effect on HIF1α, and this observation could explain the conflicting evidence for the effectiveness of metformin in men undergoing EBRT for PCa. Higher, more toxic doses of metformin may be required to inhibit the mammalian target of rapamycin-HIF1α pathway in this patient group.

Zinc preconditioning protects against renal ischaemia reperfusion injury in a preclinical sheep large animal model.

Ischaemia-reperfusion injury (IRI) during various surgical procedures, including partial nephrectomy for kidney cancer or renal transplantation, is a major cause of acute kidney injury and chronic kidney disease. Currently there are no drugs or methods for protecting human organs, including the kidneys, against the peril of IRI. The aim of this study was therefore to investigate the reno-protective effect of Zn2+ preconditioning in a clinically relevant large animal sheep model of IRI. Further the reno-protective effectiveness of Zn2+ preconditioning was tested on normal human kidney cell lines HK-2 and HEK293. Anaesthetised sheep were subjected to uninephrectomy and 60 min of renal ischaemia followed by reperfusion. Sheep were preconditioned with intravenous injection of zinc chloride prior to occlusion. Serum creatinine and urea were measured before ischaemia and for 7 days after reperfusion. HK-2 and HEK293 cells were subjected to in vitro IRI using the oxygen- and glucose-deprivation model. Zn2+ preconditioning reduced ischaemic burden determined by creatinine and urea rise over time by ~ 70% in sheep. Zn2+ preconditioning also increased the survival of normal human kidney cells subjected to cellular stress such as hypoxia, hydrogen peroxide injury, and serum starvation. Overall, our protocol incorporating specific Zn2+ dosage, number of dosages (two), time of injection (24 and 4 h prior), mode of Zn2+ delivery (IV) and testing of efficacy in a rat model, a large preclinical sheep model of IRI and cells of human origin has laid the foundation for assessment of the benefit of Zn2+ preconditioning for human applications.

Progastrin: a potential predictive marker of liver metastasis in colorectal cancer.

BACKGROUND AND AIMS: Staging of colorectal cancer often fails to discriminate outcomes of patients with morphologically similar tumours that exhibit different clinical behaviours. Data from several studies suggest that the gastrin family of growth factors potentiates colorectal cancer tumourigenesis. The aim of this study was to investigate whether progastrin expression may predict clinical outcome in colorectal cancer. METHODS: Patients with colorectal adenocarcinoma of identical depth of invasion who had not received neoadjuvant therapy were included. The patients either had stage IIa disease with greater than 3-year disease-free survival without adjuvant therapy or stage IV disease with liver metastases on staging CT. Progastrin expression in tumour sections was scored with reference to the intensity and area of immunohistochemical staining. RESULTS: Progastrin expression by stage IV tumours was significantly greater than stage IIa tumours with mean progastrin immunopositivity scores of 2.1 ± 0.2 versus 0.5 ± 0.2, respectively (P < 0.001). CONCLUSIONS: This is the first study to show that progastrin expression may be predictive of aggressive tumour behaviour in patients with colorectal cancer and supports its clinical relevance and potential use as a biomarker.

FRAX597, a PAK1 inhibitor, synergistically reduces pancreatic cancer growth when combined with gemcitabine.

BACKGROUND: Pancreatic ductal adenocarcinoma remains one of the most lethal of all solid tumours. Treatment options are limited and gemcitabine-based chemotherapy remains the standard of care. Although growing evidence shows that p21-activated kinase 1 (PAK1) plays a crucial role in pancreatic cancer, its role has not been fully elucidated. This study aimed to characterise the expression and functional relevance of PAK1 in pancreatic cancer. METHODS: PAK1 expression was measured in pancreatic cancer specimens by immunohistochemistry and in pancreatic cancer cell lines by western blotting. The effect of inhibition of PAK1 by either shRNA knock-down (KD), or by a selective inhibitor, FRAX597, alone or in combination with gemcitabine, on cell proliferation and migration/invasion was measured by thymidine uptake and Boyden chamber assays, respectively. The effect on tumour growth and survival was assessed in orthotopic murine models. RESULTS: PAK1 was expressed in all human pancreatic cancer samples tested, an7d was upregulated in all pancreatic cancer cell lines tested. PAK1 KD inhibited pancreatic cancer cell growth and survival, and increased sensitivity to gemcitabine treatment. AKT activity and HIF1α expression were also inhibited. FRAX597 inhibited pancreatic cancer cell proliferation, survival, and migration/invasion. When combined with gemcitabine, FRAX597 synergistically inhibited pancreatic cancer proliferation in vitro and inhibited tumour growth in vivo. CONCLUSIONS: These results implicate PAK1 as a regulator of pancreatic cancer cell growth and survival. Combination of a PAK1 inhibitor such as FRAX597 with cytotoxic chemotherapy deserves further study as a novel therapeutic approach to pancreatic cancer treatment.

Gastrin mediates resistance to hypoxia-induced cell death in xenografts of the human colorectal cancer cell line LoVo.

AIM: Gastrins act as growth factors for the normal and neoplastic colorectal mucosa. The aim of this study was to determine the role of gastrins in the response of human colorectal cancer (CRC) cells to hypoxia in vitro and in vivo. METHODS: Expression of the gastrin gene in the human CRC cell line LoVo was examined under normoxia and hypoxia by quantitative PCR and by radioimmunoassay. Gastrin expression was knocked down with shRNA, and the effect on cell proliferation was measured by cell counting, on cell apoptosis by annexin V staining, and on cell migration by Boyden chamber assay. The effect of gastrin knockdown on tumourigenesis in mouse xenografts was analysed by measurement of tumour volumes and weights, and by immunohistochemistry. RESULTS: Gastrin gene expression in LoVo cells was stimulated by hypoxia via binding of hypoxia-inducible factor-1α to the gastrin promoter. The viability of gastrin knockdown cells exposed to hypoxia (1% O2) in vitro was diminished because of loss of resistance against hypoxia-induced apoptosis, and the effect was partly reversed by treatment with non-amidated, but not amidated, gastrin. Conditioned medium from control LoVo cells under hypoxia simulated proliferation but not migration, and the effect was blocked by an inhibitor of non-amidated gastrins, but not by an inhibitor of amidated gastrins. In xenografts in mice exposed to hypoxia (10% O2) for 21days, tumour necrosis was significantly increased by knocking down gastrin expression. CONCLUSION: These results provide evidence that non-amidated gastrins are involved in the adaptation of CRCs to hypoxic microenvironments through increasing resistance to apoptosis.

HIF1α expression under normoxia in prostate cancer--which pathways to target?

PURPOSE: HIF1α over expression correlates with poor prognosis in a number of cancers. Although it is widely accepted that hypoxia induces HIF1α expression up-regulation by a reduction in oxygen dependent degradation, HIF1α up-regulation under normoxic conditions is noted with increasing frequency in many cancers. We reviewed the current knowledge of mechanisms of normoxic and hypoxic HIF1α up-regulation, and its therapeutic implications with a particular focus on its role as a potential biomarker in prostate cancer. MATERIALS AND METHODS: Although the literature on the role of HIFs in cancer development and progression has been reviewed extensively, few publications have specifically considered the role of HIFs in prostate cancer. Therefore, we searched PubMed® and Google® with the key words prostate cancer, castration resistance, metastasis, hypoxia, HIF1α, HIF2α and regulation. Relevant articles, including original research studies and reviews, were selected based on contents and a synopsis was generated. RESULTS: Normoxic expression of HIF1α has an important role in the development of prostate cancer chemoresistance, radioresistance and castrate resistance. Thus, HIF1α could serve as a potential biomarker. Furthermore, agents that target HIF1α could be used as adjuvant therapy to decrease resistance to conventional treatment modalities. HIF1α over expression in prostate cancer can be regulated at 3 levels, including transcription, translation and protein stability, by a number of mechanisms such as gene amplification, single nucleotide polymorphism, increased transcription of HIF1α mRNA, expression of truncated isoforms of HIF1α and stabilization of HIF1α. However, there is no definitive consensus and the intriguing question of how HIF1α is up-regulated in prostate cancer is still unanswered. CONCLUSIONS: HIF1α over expression under normoxia could serve as a biomarker for chemoresistance, radioresistance and castrate resistance in prostate cancer. There is an urgent need to identify the cause of HIF1α over expression in castrate resistant prostate cancer cells and tumors to guide the choice of HIF inhibitors (transcription or translation based) that are best suited for treating castrate resistant prostate cancer.

Identification of binding sites for C-terminal pro-gastrin-releasing peptide (GRP)-derived peptides in renal cell carcinoma: a potential target for future therapy.

OBJECTIVE: To determine the expression and biology of the neuroendocrine growth factor gastrin-releasing peptide (GRP) and other proGRP-derived peptides in renal cancer. MATERIALS AND METHODS: Receptor binding studies, enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay, were used to quantitate the presence of proGRP-derived peptide receptors and their ligands in renal cancer cell lines and human renal cancers. Biological activity of proGRP peptides was confirmed with proliferation, migration, and extracellular-signal-regulated kinases 1 and 2 (ERK1/2) activation assays in vitro. In vivo, ACHN renal cancer xenografts were treated with proGRP-derived peptides to assess tumour size and necrosis. hypoxia-inducible factor 1α (HIF1α) and vascular endothelial growth factor (VEGF) expression were investigated with Western blotting and ELISA respectively, to determine the possible contribution of the proGRP peptides to tumour viability. RESULTS: In ACHN cells that expressed both proGRP- and GRP-receptors, the expression of proGRP binding sites was 80-fold greater than the GRP-receptor (GRPR). C-terminal proGRP-derived peptides stimulated the activation of ERK1/2, but with a different time course to GRP, consistent with the suggestion that these peptides may have unique cellular functions. Both GRP and proGRP47-68 stimulated proliferation and migration of ACHN cells in vitro, but only GRP reduced the extent of tumour necrosis in ACHN xenografts. GRP, but not proGRP47-68, was able to induce HIF1α and VEGF expression in ACHN cells. This may account in part for the reduction in necrosis after GRP treatment. C-terminal proGRP-derived peptides were present in all three renal cancer cell lines and a panel of human renal cancers, but mature amidated GRP was absent. CONCLUSION: C-terminal proGRP peptides are more abundant in renal cancers and their cell lines than the more extensively studied amidated peptide, GRP. These results suggest that C-terminal proGRP-derived peptides may be a better target for novel renal cancer treatments.

Expression and function of gastrin-releasing peptide (GRP) in normal and cancerous urological tissues.

Gastrin-releasing peptide (GRP) acts as an important regulatory peptide in several normal physiological processes and as a growth factor in certain cancers. In this review we provide a comprehensive overview of the current state of knowledge of GRP in urological tissues under both normal and cancerous conditions. GRP and its receptor, GRP-R, are expressed in the normal kidney and renal cancers. GRP can stimulate the growth of renal cancer cells. GRP and GRP-R are expressed in prostate cancer and GRP can stimulate the growth of prostate cancer cell lines. Importantly, GRP is a key neuroendocrine peptide, which may be involved in the progression of advanced prostate cancer and in the neuroendocrine differentiation of prostate cancer. Recent animal studies have shown that GRP and GRP-R are an integral part of male sexual function and play a crucial role in spinal control of erections and ejaculation.

Ferric ions inhibit proteolytic processing of progastrin.

The gastrointestinal hormone gastrin is generated from an 80 amino acid precursor (progastrin) by cleavage after dibasic residues by prohormone convertase 1. Phosphorylation of Ser(75) has previously been suggested, on the basis of indirect evidence, to inhibit cleavage of progastrin after Arg(73)Arg(74). Gastrins bind two ferric ions with high affinity, and iron binding is essential for the biological activity of non-amidated gastrins in vitro and in vivo. This study directly investigated the effect of iron binding and of serine phosphorylation on the cleavage of synthetic progastrin-derived peptides. The affinity of synthetic progastrin(55-80) for ferric ions, and the rate of cleavage by prohormone convertase 1, were not affected by phosphorylation of Ser(75). In contrast, in the presence of ferric ions the rate of cleavage of both progastrin(55-80) and phosphoSer(75)progastrin(55-80) by prohormone convertase 1 was significantly reduced. Hence iron binding to progastrin may regulate processing and secretion in vivo, and regulation may be particularly important in diseases with altered iron homeostasis.

Zinc Preconditioning Provides Cytoprotection following Iodinated Contrast Media Exposure in In Vitro Models.

Methods: Normal human proximal renal kidney cells (HK-2) were preconditioned with either increasing doses of ZnCl2 or control. Following this preconditioning, cells were exposed to increasing concentrations of Iohexol 300 mg I2/ml for four hours. Key outcome measures included cell survival (MTT colorimetric assay) and ROS generation (H2DCFDA fluorescence assay). Results: Contrast media induced a dose-dependent reduction in survival of HK-2 cells. Compared to control, contrast media at 150, 225, and 300 mg I2/ml resulted in 69.5% (SD 8.8%), 37.3% (SD 4.8%), and 4.8% (SD 6.6%) cell survival, respectively (p < 0.001). Preconditioning with 37.5 µM and 50 µM ZnCl2 increased cell survival by 173% (SD 27.8%) (p < 0.001) and 219% (SD 32.2%) (p < 0.001), respectively, compared to control preconditioning. Zinc preconditioning resulted in a reduction of ROS generation. Zinc pre-conditioning with 37.5 µM µM ZnCl2 reduced ROS generation by 46% (p < 0.001) compared to control pre-conditioning. Conclusions: Zinc preconditioning reduces oxidative stress following exposure to radiographic contrast media which in turn results in increased survival of renal cells. Translation of this in vitro finding in animal models will lay the foundation for future use of zinc preconditioning against contrast induced nephropathy.

The Protective Effect of Zinc Against Liver Ischaemia Reperfusion Injury in a Rat Model of Global Ischaemia.

BACKGROUND: Ischaemia-reperfusion injury (IRI) is a major obstacle during liver transplantation and resection surgeries for cancer, with a need for effective and safe drugs to reduce IRI. Zinc preconditioning has been shown to protect against liver IRI in a partial (70%) ischaemia model. However, its efficacy against a clinically relevant Pringle manoeuvre that results in global liver ischaemia (100%) is unknown. AIMS: The aim of this study was to test the efficacy of zinc preconditioning in a rat model of global liver ischaemia. METHODS: Rats were preconditioned via subcutaneous injection of 10 mg/kg of ZnCl2, 24 h and 4 h before ischaemia. Total liver ischaemia (100%) was induced by placing a clamp across the portal triad for 30 min. Liver injury was assessed by serum alanine transaminase (ALT) and aspartate transaminase (AST) levels in blood taken before ischaemia (baseline) and at 1, 2, 4, 24, 48, 72, 96 and 120 hours after ischaemia. Animals were culled after 7 days, and the harvested livers were histologically analysed. RESULTS: On a two-way repeated-measures analysis of variance, there was a statistically significant (p = 0.025) difference in the mean ALT levels between saline- and ZnCl2-treated groups. Specifically at 24 h after ischaemia, the ALT (341 ± 99 U/L) and AST (606 ± 78 U/L) in the zinc-treated group were significantly less than the ALT (2863 ± 828 U/L) and AST (3591 ± 948 U/L) values in the saline-treated group. Zinc significantly reduced neutrophil infiltration and necrosis compared with the saline control. CONCLUSION: Zinc preconditioning reduces the overall hepatocellular damage from IRI. These results lay the foundation to assess the benefit of zinc preconditioning for clinical applications.

Randomised controlled trial for high-dose intravenous zinc as adjunctive therapy in SARS-CoV-2 (COVID-19) positive critically ill patients: trial protocol.

INTRODUCTION: SARS-CoV-2 (COVID-19) has caused an international pandemic of respiratory illness, resulting in significant healthcare and economic turmoil. To date, no robust vaccine or treatment has been identified. Elemental zinc has previously been demonstrated to have beneficial effects on coronaviruses and other viral respiratory infections due to its effect on RNA polymerase. Additionally, zinc has well-demonstrated protective effects against hypoxic injury-a clear mechanism of end-organ injury in respiratory distress syndrome. We aimed to assess the effect of high-dose intravenous zinc (HDIVZn) on SARS-CoV-2 infection. The end of study analyses will evaluate the reduction of impact of oxygen saturations or requirement of oxygen supplementation. METHODS AND ANALYSIS: We designed a double-blind randomised controlled trial of daily HDIVZn (0.5 mg/kg) versus placebo. Primary outcome measures are lowest oxygen saturation (or greatest level of supplemental oxygenation) for non-ventilated patients and worst PaO2/FiO2 for ventilated patients. Following power calculations, 60 hospitalised patients and 100 ventilated patients will be recruited to demonstrate a 20% difference. The duration of follow-up is up to the point of discharge. ETHICS AND DISSEMINATION: Ethical approval was obtained through the independent Human Research Ethics Committee. Participant recruitment will commence in May 2020. Results will be published in peer-reviewed medical journals. TRIAL REGISTRATION NUMBER: ACTRN126200000454976.

Gastrin-releasing peptide: different forms, different functions.

All forms of the neuropeptide gastrin-releasing peptide (GRP) are derived from the precursor proGRP1-125. Amidated GRP18-27, which together with amidated GRP1-27 was long thought to be the only biologically relevant product of the GRP gene, is involved in a multitude of physiological functions and acts as a mitogen, morphogen, and proangiogenic factor in certain cancers. Recently, GRP has been implicated in several psychiatric conditions, in the maintenance of circadian rhythm, in spinal transmission of the itch sensation, and in inflammation and wound repair. The actions of GRP are mediated by the GRP receptor. Over the last decade, nonamidated peptides derived from proGRP, such as the glycine-extended form GRP18-28 and recombinant and synthetic fragments from proGRP31-125, have been shown to be biologically active in a range of tissues and in cancer cell lines. While GRP18-28 acts via the GRP receptor, the identity of the receptor for proGRP31-125 and its fragments has not yet been established. Nonamidated fragments are also present in normal tissues and in various cancers. In fact, proGRP31-98 is the most sensitive serum biomarker in patients with small cell lung cancer and is a significant predictor of poor survival in patients with advanced prostate cancer.

Why is it worth testing the ability of zinc to protect against ischaemia reperfusion injury for human application.

Ischaemia (interruption in the blood/oxygen supply) and subsequent damage induced by reperfusion (restoration of blood/oxygen supply) ultimately leads to cell death, tissue injury and permanent organ dysfunction. The impact of ischaemia reperfusion injury (IRI) is not limited to heart attack and stroke but can be extended to patients undergoing surgeries such as partial nephrectomy for renal cancer, liver resection for colorectal cancer liver metastasis, cardiopulmonary bypass, and organ transplantation. Unfortunately, there are no drugs that can protect organs against the inevitable peril of IRI. Recent data show that a protocol incorporating specific Zn formulation, dosage, number of dosages, time of injection, and mode of Zn delivery (intravenous) and testing of efficacy in a large preclinical sheep model of IRI strongly supports human trials of Zn preconditioning. No doubt, scepticism still exists among funding bodies and research fraternity on whether Zn, a naturally occurring metal, will work where everything else has failed. Therefore, in this article, we review the conflicting evidence on the promoter and protector role of Zn in the case of IRI and highlight factors that may help explain the contradictory evidence. Finally, we review the literature related to the knowledge of Zn's mechanism of action on ROS generation, apoptosis, HIF activation, inflammation, and signal transduction pathways, which highlight Zn's likelihood of success compared to various other interventions targeting IRI.

Corrigendum to "Targeting HIF-1α to Prevent Renal Ischemia-Reperfusion Injury: Does It Work?"

[This corrects the article DOI: 10.1155/2018/9852791.].

Preconditioning against renal ischaemia reperfusion injury: the failure to translate to the clinic.

Acute kidney injury (AKI) as a result of ischaemia-reperfusion represents a major healthcare burden worldwide. Mortality rates from AKI in hospitalized patients are extremely high and have changed little despite decades of research and medical advances. In 1986, Murry et al. demonstrated for the first time the phenomenon of ischaemic preconditioning to protect against ischaemia-reperfusion injury (IRI). This seminal finding paved the way for a broad body of research, which attempted to understand and ultimately harness this phenomenon for human application. The ability of preconditioning to limit renal IRI has now been demonstrated in multiple different animal models. However, more than 30 years later, a safe and consistent method of protecting human organs, including the kidneys, against IRI is still not available. This review highlights agents which, despite strong preclinical data, have recently failed to reduce AKI in human trials. The multiple reasons which may have contributed to the failure to translate some of the promising findings to clinical therapies are discussed. Agents which hold promise in the clinic because of their recent efficacy in preclinical large animal models are also reviewed.

Targeting HIF-1α to Prevent Renal Ischemia-Reperfusion Injury: Does It Work?

Partial nephrectomy (open or minimally invasive) usually requires temporary renal arterial occlusion to limit intraoperative bleeding and improve access to intrarenal structures. This is a time-critical step due to the critical ischemia period of renal tissue. Prolonged renal ischemia may lead to irreversible nephron damage in the remaining tissue and, ultimately, chronic kidney disease. This is potentiated by the incompletely understood ischemia-reperfusion injury (IRI). A key mechanism in IRI prevention appears to be the upregulation of an intracellular transcription protein, Hypoxia-Inducible Factor (HIF). HIF mediates metabolic adaptation, angiogenesis, erythropoiesis, cell growth, survival, and apoptosis. Upregulating HIF-1α via ischemic preconditioning (IPC) or drugs that simulate hypoxia (hypoxia-mimetics) has been investigated as a method to reduce IRI. While many promising chemical agents have been trialed for the prevention of IRI in small animal studies, all have failed in human trials. The aim of this review is to highlight the techniques and drugs that target HIF-1α and ameliorate IRI associated with renal ischemia. Developing a technique or drug that could reduce the risk of acute kidney injury associated with renal IRI would have an immediate worldwide impact on multisystem surgeries that would otherwise risk ischemic tissue injury.

Zinc ion dyshomeostasis increases resistance of prostate cancer cells to oxidative stress via upregulation of HIF1α.

Zinc ions (Zn2+) are known to influence cell survival and proliferation. However the homeostatic regulation of Zn2+ and their role in prostate cancer (PC) progression is poorly understood. Therefore the subcellular distribution and uptake of Zn2+ in PC cells were investigated. Inductively coupled plasma mass spectroscopy and fluorescent microscopy with the Zn2+-specific fluorescent probe FluoZin-3 were used to quantify total and free Zn2+, respectively, in the normal prostate epithelial cell line (PNT1A) and three human PC cell lines (PC3, DU145 and LNCaP). The effects of Zn2+ treatment on proliferation and survival were measured in vitro using MTT assays and in vivo using mouse xenografts. The ability of Zn2+ to protect against oxidative stress via a HIF1α-dependent mechanism was investigated using a HIF1α knock-down PC3 model. Our results demonstrate that the total Zn2+ concentration in normal PNT1A and PC cells is similar, but PC3 cells contain significantly higher free Zn2+ than PNT1A cells (p < 0.01). PNT1A cells can survive better in the presence of high concentrations of Zn2+ than PC3 cells. Exposure to 10 µM Zn2+ over 72 hours significantly reduces PC3 cell proliferation in vitro but not in vivo. Zn2+ increases PC3 cell survival up to 2.3-fold under oxidative stress, and this protective effect is not seen in PNT1A cells or in a HIF1α-KD PC3 cell model. A state of Zn2+ dyshomeostasis exists in PC. HIF1α is an integral component of a Zn2+-dependent protective mechanism present in PC3 cells. This pathway may be clinically significant through its contribution to castrate-resistant PC survival.