Tempol

Tempol is a superoxide scavenger (superoxide dismutase mimetic). It is a member of non-thiol-containing radiation protectors that can permeate the membrane.

In vitro, Tempol disrupted H2O2-mediated reduction in mitochondrial respiration and increase in LDH secretion from rat PT cells, suggesting in a decrease in cell injury and death, [1]. In human prostate cancer cell, Tempol activated uPAR (urokinase receptor) [2].

In vivo, Tempol treatment showed 1) renal function and injury improvement 2) PMN infiltration and lipid peroxidation reduction 3) reduced nitrosative and oxidative stress [1]. In cirrhotic rats, Tempol decreased portal pressure and raised portal blood flow [3]. In 2K1C rats, Tempol inhibited upregulation of TGF-beat and MMPs, and prevented changes of cardiac hypertensive [4]. It also prevented cerebral vessel remodeling in hypertensive rats [5].

References:
1. Chatterjee PK, Cuzzocrea S, Brown PA et al. Tempol, a membrane-permeable radical scavenger, reduces oxidant stress-mediated renal dysfunction and injury in the rat. Kidney Int. 2000 Aug;58(2):658-73.
2.  Lejeune D, Hasanuzzaman M, Pitcock A et al. The superoxide scavenger TEMPOL induces urokinase receptor (uPAR) expression in human prostate cancer cells. Mol Cancer. 2006 Jun 6;5:21.
3.  García-Calderó H, Rodríguez-Vilarrupla A, Gracia-Sancho J et al. Tempol administration, a superoxide dismutase mimetic, reduces hepatic vascular resistance and portal pressure in cirrhotic rats. J Hepatol. 2011 Apr;54(4):660-5.
4.  Rizzi E, Castro MM, Ceron CS et al. Tempol inhibits TGF-β and MMPs upregulation and prevents cardiac hypertensive changes. Int J Cardiol. 2013 Apr 30;165(1):165-73.
5.  Pires PW, Deutsch C, McClain JL et al. Tempol, a superoxide dismutase mimetic, prevents cerebral vessel remodeling in hypertensive rats. Microvasc Res. 2010 Dec;80(3):445-52.

Tempol (4 hydroxy-tempo) inhibits anoxia-induced progression of mitochondrial dysfunction and associated neurobehavioral impairment in neonatal rats.[Pubmed:28320189]

J Neurol Sci. 2017 Apr 15;375:58-67.

BACKGROUND: Anoxia leads to a robust generation of reactive oxygen species/nitrogen species which can result in mitochondrial dysfunction and associated cell death in the cerebral cortex of neonates. AIM: The present study investigated the pharmacological role of Tempol in the treatment of rat neonatal cortical mitochondrial dysfunction induced insult progression (day-1 to day-7) and associated neurobehavioral alterations post-anoxia. METHODS: Rat pups of 30h age or postnatal day 2 (PND2) were randomly divided into 5 groups (n=5 per group): (1) Control; (2) Anoxia; (3) Anoxia+Tempol 75mg/kg; (4) Anoxia+Tempol 150mg/kg; and (5) Anoxia+Tempol 300mg/kg, and subjected to two episode of anoxia (10min each) at 24h of time interval in an enclosed chamber supplied with 100% N2. RESULTS: Tempol significantly decreased nitric oxide (NO) formation and simultaneously improved superoxide dismutase (SOD) and catalase (CAT) activities. Further, we observed a significantly (P<0.05) improvement in mitochondrial respiration, complex enzyme activities, mitochondrial membrane potential (MMP) along with attenuation of transition pore opening (MPT) after treatment with Tempol. Furthermore, Tempol decreased expression of mitochondrial Bax, cytochrome-C, caspase-9 and caspase-3 while the increase in expression of cytoplasmic Bax, mitochondrial Bcl-2 on day-7 in cortical region indicating regulation of intrinsic pathway of apoptosis. Further, it improved anoxia-induced neurobehavioral outcome (hanging and reflex latencies). CONCLUSION: Biochemical, molecular and behavioral studies suggest the role of Tempol in preserving mitochondrial function and associated neurobehavioral outcomes after neonatal anoxia.

Effects of Tempol and Quercetin on Human Sperm Function after Cryopreservation.[Pubmed:28376137]

Cryo Letters. 2017 Jan/Feb;38(1):29-36.

BACKGROUND: Quercetin is a flavonoid with high reactive oxygen species (ROS) scavenging and ion chelating activity. It also enhances the activity of antioxidant enzymes and reduces enzymatic activity such as NADPH oxidase and NADH-dependent oxido-reductase. Tempol, as a superoxide dismutase mimetic agent, converts superoxide to less toxic hydrogen peroxide (H2O2), but cannot reduce highly toxic hydroxyl radicals in Fenton or Haber-Weiss reactions mediated with free iron or cupper. OBJECTIVE: The study was to compare the effect of Quercetin and Tempol in an optimized commercial cryo-protective media on ROS induced cryoinjury for the first time. MATERIALS AND METHODS: Following administration of these compounds during freezing process, sperm motility, viability, ROS production and DNA integrity were assessed before and after freezing/thawing process. RESULTS: Data showed that 10 microM Quercetin and 5 microM Tempol significantly improved sperm motility and viability, but they together had no additive effect. Supplementation with Quercetin alone or combination of Quercetin with Tempol decrease the ROS concentration, but the reduction was not significant for Tempol alone compared to control group. Quercetin and Tempol significantly decrease DNA fragmentation. CONCLUSION: The supplementation of Quercetin or Tempol, but not their combination improves the quality of cryopreserved human semen.

Effect of Tempol on the prevention of irradiation-induced mucositis in miniature pigs.[Pubmed:28326646]

Oral Dis. 2017 Sep;23(6):801-808.

OBJECTIVE: The goals of this study were to (i) establish a useful miniature pig (minipig) model for irradiation-induced oral mucositis and (ii) evaluate the effect of Tempol to prevent its development. METHODS AND MATERIALS: Minipigs were irradiated with 6 Gy for five consecutive days targeting the entire oral cavity. To prevent radiation damage, minipigs were treated with 30 mg kg(-1) Tempol 10 min before irradiation (n = 4), while the radiation-alone group was similarly injected with saline (n = 4). Lesions were graded using an oral mucositis score and visual inspection every 3 days, and biopsy of multiple sites was performed at day 18. Weight and chest and abdominal circumferences were measured every 3 days. RESULTS: Lesions began about 12 days after the first irradiation fraction and healed about 30 days after irradiation. Epithelial thickness was calculated on the lingual and buccal mucosa on the 18th day after the first irradiation fraction. Tempol provided modest protection from ulceration after irradiation using this treatment strategy. CONCLUSIONS: This study established a useful large animal model for irradiation-induced oral mucositis and showed modest beneficial effects of Tempol in limiting tissue damage. The latter finding may be potentially valuable in preventing oral mucositis in patients receiving irradiation for head and neck cancers.

Oral administration of the nitroxide radical TEMPOL exhibits immunomodulatory and therapeutic properties in multiple sclerosis models.[Pubmed:28238951]

Brain Behav Immun. 2017 May;62:332-343.

Therapies with both immunomodulatory and neuroprotective properties are thought to have the greatest promise in reducing the severity and progression of multiple sclerosis (MS). Several reactive oxygen (ROS) and reactive nitrogen species (RNS) are implicated in inflammatory-mediated damage to the central nervous system (CNS) in MS and its animal model, experimental autoimmune encephalomyelitis (EAE). Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) is a stable nitroxide radical with potent antioxidant activity. The goal of our studies was to investigate the immunomodulatory effects and therapeutic potential of orally-delivered Tempol in the mouse EAE model. Mice receiving Tempol chow ad libitum for 2weeks prior to induction of active EAE showed delayed onset and reduced incidence of disease compared to control-fed animals. Reduced disease severity was associated with limited microglial activation and fewer inflammatory infiltrates. Tempol's effects were immunomodulatory, not immunosuppressive: T cells produced less interferon-gamma and tumor necrosis factor-alpha, and Tempol-fed mice exhibited a shift towards TH2-type antibody responses. Both myeloid and myeloid-dendritic cells of Tempol-fed EAE animals had significantly lower levels of MHC class II expression than controls; CD40 was also significantly reduced. Tempol administration was associated with an enrichment of CD8(+) T cell populations and CD4(+)FoxP3(+) regulatory populations. Tempol reduced the severity of clinical disease when administered after the induction of disease, and also after the onset of clinical symptoms. To exclude effects on T cell priming in vivo, Tempol was tested with the passive transfer of encephalitogenic T cells and was found to reduce the incidence and peak severity of disease. Protection was associated with reduced infiltrates and a relative sparing of neurofilaments and axons. The ability of oral Tempol to reduce inflammation and axonal damage and loss demonstrate both anti-inflammatory and protective properties, with significant promise for the treatment of MS and related neurological disorders.

Neuroprotective effects of tempol, a catalytic scavenger of peroxynitrite-derived free radicals, in a mouse traumatic brain injury model.[Pubmed:18319733]

J Cereb Blood Flow Metab. 2008 Jun;28(6):1114-26.

We examined the ability of Tempol, a catalytic scavenger of peroxynitrite (PN)-derived free radicals, to reduce cortical oxidative damage, mitochondrial dysfunction, calpain-mediated cytoskeletal (alpha-spectrin) degradation, and neurodegeneration, and to improve behavioral recovery after a severe (depth 1.0 mm), unilateral controlled cortical impact traumatic brain injury (CCI-TBI) in male CF-1 mice. Administration of a single 300 mg/kg intraperitoneal dose of Tempol 15 mins after TBI produced a complete suppression of PN-mediated oxidative damage (3-nitrotyrosine, 3NT) in injured cortical tissue at 1 h after injury. Identical Tempol dosing maintained respiratory function and attenuated 3NT in isolated cortical mitochondria at 12 h after injury, the peak of mitochondrial dysfunction. Multiple dosing with Tempol (300 mg/kg intraperitoneally at 15 mins, 3, 6, 9, and 12 h) also suppressed alpha-spectrin degradation by 45% at its 24 h post-injury peak. The same dosing regimen improved 48 h motor function and produced a significant, but limited (17.4%, P<0.05), decrease in hemispheric neurodegeneration at 7 days. These results are consistent with a mechanistic link between PN-mediated oxidative damage to brain mitochondria, calpain-mediated proteolytic damage, and neurodegeneration. However, the modest neuroprotective effect of Tempol suggests that multitarget combination strategies may be needed to interfere with posttraumatic secondary injury to a degree worthy of clinical translation.

The superoxide scavenger TEMPOL induces urokinase receptor (uPAR) expression in human prostate cancer cells.[Pubmed:16756681]

Mol Cancer. 2006 Jun 6;5:21.

There is little understanding of the effect that reactive oxygen metabolites have on cellular behavior during the processes of invasion and metastasis. These oxygen metabolites could interact with a number of targets modulating their function such as enzymes involved in basement membrane dissolution, adhesion molecules involved in motility or receptors involved in proliferation. We investigated the effect of increased scavenging of superoxide anions on the expression of the urokinase receptor (uPAR) in PC-3M human prostate cancer cells. Urokinase receptor is a GPI-linked cell surface molecule which mediates multiple functions including adhesion, proliferation and pericellular proteolysis. Addition of the superoxide scavenger 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (Tempol) to PC-3M cultures stimulated expression of uPAR protein peaking between 48 and 72 hours. Cell surface expression of the uPAR was also increased. Surprisingly, uPAR transcript levels increased only slightly and this mild increase did not coincide with the striking degree of protein increase. This disparity indicates that the Tempol effect on uPAR occurs through a post-transcriptional mechanism. Tempol presence in PC-3M cultures reduced intracellular superoxide-type species by 75% as assayed by NBT dye conversion; however this reduction significantly diminished within hours following Tempol removal. The time gap between Tempol treatment and peak uPAR protein expression suggests that reduction of reactive oxygen metabolites in prostate cancer cells initiates a multistep pathway which requires several hours to culminate in uPAR induction. These findings reveal a novel pathway for uPAR regulation involving reactive oxygens such as superoxide anion.