Cancer as a Channelopathy-Appreciation of Complimentary Pathways Provides a Different Perspective for Developing Treatments.

Life depends upon the ability of cells to evaluate and adapt to a constantly changing environment and to maintain internal stability to allow essential biochemical reactions to occur. Ions and ion channels play a crucial role in this process and are essential for survival. Alterations in the expression of the transmembrane proteins responsible for maintaining ion balance that occur as a result of mutations in the genetic code or in response to iatrogenically induced changes in the extracellular environment is a characteristic feature of oncogenesis and identifies cancer as one of a constellation of diseases known as channelopathies. The classification of cancer as a channelopathy provides a different perspective for viewing the disease. Potentially, it may expand opportunities for developing novel ways to affect or reverse the deleterious changes that underlie establishing and sustaining disease and developing tolerance to therapeutic attempts at treatment. The role of ions and ion channels and their interactions in the cell's ability to maintain ionic balance, homeostasis, and survival are reviewed and possible approaches that mitigate gain or loss of ion channel function to contribute to new or enhance existing cancer therapies are discussed.

Effect of Cell Cycle on Cell Surface Expression of Voltage-Gated Sodium Channels and Na+,K+-ATPase.

Voltage-gated sodium channels (VGSCs) are the target for many therapies. Variation in membrane potential occurs throughout the cell cycle, yet little attention has been devoted to the role of VGSCs and Na+,K+-ATPases. We hypothesized that in addition to doubling DNA and cell membrane in anticipation of cell division, there should be a doubling of VGSCs and Na+,K+-ATPase compared to non-dividing cells. We tested this hypothesis in eight immortalized cell lines by correlating immunocytofluorescent labeling of VGSCs or Na+,K+-ATPase with propidium iodide or DAPI fluorescence using flow cytometry and imaging. Cell surface expression of VGSCs during phases S through M was double that seen during phases G0-G1. By contrast, Na+,K+-ATPase expression increased only 1.5-fold. The increases were independent of baseline expression of channels or pumps. The variation in VGSC and Na+,K+-ATPase expression has implications for both our understanding of sodium's role in controlling the cell cycle and variability of treatments targeted at these components of the Na+ handling system.

The Role of Targeted Osmotic Lysis in the Treatment of Advanced Carcinoma in Companion Animals: A Case Series.

Background: Targeted osmotic lysis (TOL) is a novel technology that involves concomitant stimulation of voltage-gated sodium channels (VGSCs) and the pharmacological blockade of Na+, K+-ATPase causing lysis of highly malignant cancer cells. Hypothesis/Objectives. TOL offers an option for treating advanced carcinomas in companion animals. Animals. Two cats and 2 dogs that presented to veterinary hospitals for evaluation and treatment of one of several forms of carcinoma. Methods: Digoxin was administered to achieve steady-state, therapeutic concentrations. The animals were then exposed to pulsed electric field stimulation. Pre- and posttreatment assessments of tumor size and quality of life were compared. The treatment frequency and survivability varied, based on the patient's premorbid functioning and response to treatment. Results: Regardless of cancer type, TOL consistently increased survival beyond expected, often improving, but without compromising of quality of life. Conclusions and Clinical Importance. TOL warrants consideration as an option for managing advanced carcinomas.

Targeted Osmotic Lysis: A Novel Approach to Targeted Cancer Therapies.

The conventional treatment of cancer has been based on the delivery of non-selective toxins and/or ionizing energy that affect both the cancer and normal tissues in the hope of destroying the offending disease before killing the patient. Unfortunately, resistance often develops to these treatments and patients experience severe, dose-limiting adverse effects that reduce treatment efficacy and compromise quality of life. Recent advances in our knowledge of the biology of tumor cells and their microenvironment, the recognition of surface proteins that are unique to specific cancers and essential to cell growth and survival and signaling pathways associate with invasion and metastasis have led to the development of targeted therapies that are able to identify specific cellular markers and more selectively deliver lethal treatment to the invading cancer thus improving efficacy and limiting adverse effects. In the context of targeted approaches to cancer therapy, we present targeted osmotic lysis as a novel and fundamentally different approach for treating advanced-stage carcinoma that exploits the conserved relationship between voltage-gated sodium channels and Na+, K+-ATPase and has the potential to increase survival without compromising quality of life in a broad spectrum of highly malignant forms of cancer.

Emergency Use of Targeted Osmotic Lysis for the Treatment of a Patient with Aggressive Late-Stage Squamous Cell Carcinoma of the Cervix.

Upregulation of voltage-gated sodium channels (VGSCs) and Na+/K+-ATPase (sodium pumps) is common across most malignant carcinomas. Targeted osmotic lysis (TOL) is a developing technology in which the concomitant stimulation of VGSCs and pharmacological blockade of sodium pumps causes rapid selective osmotic lysis of carcinoma cells. This treatment of cervical carcinoma is evidence that TOL is a safe, well-tolerated and effective treatment for aggressive advanced carcinomas that has the potential to extend life without compromising its quality. TOL is likely to have broad application for the treatment of advanced-stage carcinomas.

Targeted Osmotic Lysis of Highly Invasive Breast Carcinomas Using Pulsed Magnetic Field Stimulation of Voltage-Gated Sodium Channels and Pharmacological Blockade of Sodium Pumps.

Abstract: Concurrent activation of voltage-gated sodium channels (VGSCs) and blockade of Na+ pumps causes a targeted osmotic lysis (TOL) of carcinomas that over-express the VGSCs. Unfortunately, electrical current bypasses tumors or tumor sections because of the variable resistance of the extracellular microenvironment. This study assesses pulsed magnetic fields (PMFs) as a potential source for activating VGSCs to initiate TOL in vitro and in vivo as PMFs are unaffected by nonconductive tissues. In vitro, PMFs (0-80 mT, 10 msec pulses, 15 pps for 10 min) combined with digoxin-lysed (500 nM) MDA-MB-231 breast cancer cells stimulus-dependently. Untreated, stimulation-only, and digoxin-only control cells did not lyse. MCF-10a normal breast cells were also unaffected. MDA-MB-231 cells did not lyse in a Na+-free buffer. In vivo, 30 min of PMF stimulation of MDA-MB-231 xenografts in J/Nu mice or 4T1 homografts in BALB/c mice, concurrently treated with 7 mg/kg digoxin reduced tumor size by 60-100%. Kidney, spleen, skin and muscle from these animals were unaffected. Stimulation-only and digoxin-only controls were similar to untreated tumors. BALB/C mice with 4T1 homografts survived significantly longer than mice in the three control groups. The data presented is evidence that the PMFs to activate VGSCs in TOL provide sufficient energy to lyse highly malignant cells in vitro and to reduce tumor growth of highly malignant grafts and improve host survival in vivo, thus supporting targeted osmotic lysis of cancer as a possible method for treating late-stage carcinomas without compromising noncancerous tissues.

Selective lysis of breast carcinomas by simultaneous stimulation of sodium channels and blockade of sodium pumps.

Sodium influx through voltage-gated sodium channels (VGSCs) coupled with balanced removal of sodium ions via Na+, K+-ATPase is a major determinant of cellular homeostasis and intracellular ionic concentration. Interestingly, many metastatic carcinomas express high levels of these channels. We hypothesized that if excess VGSCs are activated and Na+, K+-ATPase is simultaneously blocked, the intracellular Na+ concentration should increase, resulting in water movement into the cell, causing swelling and lytic cell death. MDA-MB-231 breast cancer cells over-express VGSCs by 7-fold. To test our hypothesis, we treated these cells in vitro with the Na+, K+-ATPase blocker, ouabain, and then stimulated with a sublethal electric current. For in vivo histologic and survival studies, MDA-MB-231 xenografts were established in Nu/J mice. Mice injected with saline or ouabain were electrically stimulated with trains of 10 msec 10V DC pulses. Within seconds to minutes, the cells swelled and lysed. MCF-10a cells, which express normal VGSCs levels, were unaffected by this treatment. Cells from the weakly-malignant cell line, MCF-7, which express 3-fold greater VGSCs than MCF-10a cells, displayed an intermediate time-to-lysis. The rate of lysis correlated directly with the degree of sodium channel expression and malignancy. We also demonstrated efficacy in cell lines from prostate, colon and lung carcinomas. Treated MDA-MB-231 xenografts showed 60-80% cell death. In survival studies, TOL-treated mice showed significantly slower tumor growth vs. controls. These results are evidence that this "targeted osmotic lysis" represents a novel method for selectively killing cancer cells and warrants further investigation as a potential treatment for advanced and end-stage breast cancer.

Chronic Daily Headache: Mechanisms and Principles of Management.

Primary headache is a common malady that is often under-recognized and frequently inadequately managed in spite of the fact that it affects up to 95 % of the population in a lifetime. Many forms of headache, including episodic tension and migraine headaches, if properly diagnosed, are reasonably amenable to treatment, but a smaller, though not insignificant, percent of the population suffer daily from a chronic, intractable form of headache that destroys one's productivity and quality of life. These patients are frequently seen in neurological practices at a point when treatment options are limited and largely ineffective. In the following review, we will discuss mechanisms drawn from recent studies that address the transition from acute to chronic pain that may apply to the transformation from episodic to chronic daily headaches which may offer opportunities for preempting headache transformation.

Critical appraisal of extended-release hydrocodone for chronic pain: patient considerations.

Opioid analgesics are currently the most effective pharmacologic option for the management of both acute and chronic forms of moderate-to-severe pain. Although the "as-needed" use of immediate-release formulations is considered optimum for treating acute, painful episodes of limited duration, the scheduled dosing of extended-release formulations with immediate-release supplementation for breakthrough pain is regarded to be most effective for managing chronic conditions requiring around-the-clock treatment. The recent introduction of extended-release formulations of the opioid analgesic hydrocodone potentially broadened the possibility of providing pain relief for individuals for whom current formulations are either ineffective or not tolerated. However, reaction to the approval of the new formulations has fueled controversy over the general safety and need for opioid medications, in light of their potential for misuse, abuse, diversion, and addiction. Here, we discuss how the approval of extended-release formulations of hydrocodone and the emotionally charged controversy over their release may affect physician prescribing and the care available to patients in need of chronic opioid therapy for the management of pain.

A plea for rational mitigation of poor outcomes in the 'off-label use' of medications for the management of pain.

Neuropathic pain is a common and difficult to manage public health problem characterized by frequent treatment failure and high management costs. The variable presentation and response to treatment among patients make it difficult for physicians to apply a single, standardized approach for management. The physician's role in treating neuropathic pain is complex. Clinical decisions must be drawn from personal and shared experience, case reports, and evidence-based, controlled trials performed on selected populations of patients with common, narrowly-defined conditions. Recent advances in our understanding of the mechanisms that underlie the processing of nociceptive stimuli and the perception of pain have led to the increased 'off-label use' of adjuvant medications in an attempt to provide relief for many patients who heretofore have suffered unnecessarily with intractable neuropathic pain. Unfortunately, as with any treatment, sound clinical decisions can occasionally result in an untoward adverse response. It is therefore imperative that potential adverse effects inherent to all medications be considered and weighed against the untoward consequences of withholding treatment prior to incorporating their use in any course of management. This commentary presents a case report that illustrates a particularly devastating consequence that was encountered when a medication was selected for 'off-label use' in the treatment of intractable pain and presents an opinion for consideration in developing guidelines for determining acceptable risk and standard of care based upon rational adherence or deviation from the approved indications offered for the use of a medication at the time of its introduction into practice is granted.

Hydrocodone extended-release: pharmacodynamics, pharmacokinetics and behavioral pharmacology of a controversy.

Recently, the U.S. Food and Drug Administration (FDA) approved Zohydro(®), an extended release formulation of the opioid analgesic hydrocodone that contains no acetaminophen. This approval was against the recommendation of the FDA's Expert Panel. Subsequently, both chronic pain advocates and anti-drug abuse advocates have steadfastly expressed their support of, or astonishment at this decision. Here, we review the pharmacokinetics, pharmacodynamics, safety and abuse liability of this hydrocodone formulation and how it relates to the Expert Panel's opinion and the FDA decision. We discuss the important issues, risk mitigation, potential use of abuse deterrents, and how the different viewpoints of the Expert Panel and FDA decision makers resulted in the approval and subsequent controversy.

Ranolazine attenuates mechanical allodynia associated with demyelination injury.

OBJECTIVE: The aim of this study was to determine whether ranolazine, a new medication that targets sodium channels to improve cardiac ischemia and angina, could be an effective analgesic agent for pain associated with demyelination injury. BACKGROUND: Many agents have been used to treat neuropathic pain but not all neuropathic conditions respond similarly to treatment. We have demonstrated that ranolazine, an agent that blocks voltage-gated sodium channels Nav 1.4, 1.5, 1.7, and 1.8, is effective in attenuating mechanical hyperalgesia in both complete Freund's adjuvant and spared nerve injury preclinical models of inflammatory and neuropathic pain, respectively. Here we test the efficacy of this drug in a newly validated model of demyelination injury that responds uniquely to a number of treatment options. METHODS: After determination of baseline nerve conduction velocities (NCVs) and withdrawal responses from heat and mechanical stimulation in male Sprague-Dawley rats (300-350 g), 1 µg/30 µL of doxorubicin was injected into one sciatic nerve. The contralateral nerve provided a sham-injected control. Two weeks after doxorubicin injection, NCV and sensitivity to heat and mechanical stimulation were reassessed before and after treatment with ranolazine (10, 30, 50 mg/kg) administered intraperitoneally using an experimenter-blinded, randomized design. RESULTS: Doxorubicin injection produced a significant hyperalgesic effect in response to mechanical but not heat stimulation. Conduction velocities in the injected limbs were reduced when compared with controls. Ranolazine reduced mechanical allodynia with peak efficacy at 30 mg/kg. Fifty milligram/kilogram ranolazine restored NCVs by approximately 50%, but had no effect in the uninjected limb. CONCLUSIONS: Ranolazine exerts broad-spectrum actions to reduce mechanical allodynia that is associated with peripheral demyelination injury.

Regulation and pharmacological blockade of sodium-potassium ATPase: a novel pathway to neuropathy.

Inflammation causes upregulation of NaV1.7 sodium channels in the associated dorsal root ganglia (DRG). The resultant increase in sodium influx must be countered to maintain osmotic homeostasis. The primary mechanism to pump sodium out of neurons is Na(+), K(+)-ATPase. To test whether there is a compensatory upregulation of Na(+), K(+)-ATPase after inflammation, rats received an injection of complete Freund's adjuvant (CFA) into one hindpaw and saline into the contralateral hindpaw. Three days later, L4-L6 DRGs were extracted and analyzed using gel electrophoresis and immunohistochemistry. Immunoreactivity for both the α-1 and α-3 subunits were increased in DRG associated with CFA-treatment, compared to saline-treatment. To test whether dysregulation of Na(+), K(+)-ATPase may cause cell death after inflammation, we produced a pharmacological blockade with ouabain (10mg/kg, s.c.) three days after CFA injection and paws were stimulated or not. Twenty-four hours later, DRG were removed and stained with cresyl violet. Greater cell death was seen in DRG from ouabain-treated animals on the CFA treated side than the saline-treated side. Paw stimulation doubled this difference. Control DRG showed little neuronal death. These results are evidence that regulation of Na(+), K(+)-ATPase during major inflammatory disease states is critical for homeostatic protection of primary afferent neurons.

Morphine-induced cognitive impairment is attenuated by induced pain in rats.

Opioid medications are frequently used in the effective treatment of intractable pain, but prolonged use of such medications can be complicated by a host of adverse effects. Among these adverse effects, tolerance and mental clouding can be especially disabling and can lead to both a reduced effectiveness of treatment and a reduced quality of life for many requiring treatment with these medications. Here we examined the relative contributions of complete Freund's adjuvant (CFA)-induced inflammatory pain and opioid medication on spatial memory for a well-learned task in male Sprague-Dawley rats. Although CFA, by itself, had little effect on spatial memory, morphine administered to pain-free animals produced profound detrimental effects on spatial memory that persisted longer than the analgesic effectiveness of the drug. However, no significant cognitive deficits were observed in animals receiving morphine in the presence of CFA-induced pain. Taken together, these results are evidence that the pain state of the organism can alter some of the negative effects of morphine.

Measurement of CFA-induced hyperalgesia and morphine-induced analgesia in rats: dorsal vs plantar mechanical stimulation of the hindpaw.

OBJECTIVE: To compare the sensitivity of stimulating the plantar and dorsal hindpaw surfaces in the detection of mechanical allodynia and morphine analgesia. BACKGROUND: Several approaches are used to assess nociceptive reactivity to mechanical stimulation in animal models of pain. Although certain techniques seem to be favored for studying specific nociceptive conditions, the differences between techniques have not been directly compared and characterized. We chose to compare methods employing stimulation applied to the dorsum of the paw with stimulation of the plantar surface to demonstrate the utility of each approach in determining baseline nociceptive thresholds, changes in those thresholds after injury, and analgesic efficacy. METHODS: Withdrawal thresholds from mechanical stimulation applied to the dorsal and plantar surface of the hindpaw were measured in rats treated with morphine after receiving subcutaneous injections of complete Freund's adjuvant (CFA) using Semmes-Weinstein (S-W) monofilaments and electro von Frey (EVF) stimulation. RESULTS: In contrast to stimulation of the dorsal surface, plantar hindpaw stimulation seldom elicited an aversive withdrawal response. Differences in withdrawal response from baseline were only detectable within the first 5 hours post-CFA and only with EVF stimulation. No significant differences in stimulation techniques were observed after the initial 5-hour window. Effective dose 50 (ED(50)) for analgesic efficacy was consistently lower using dorsal stimulation. CONCLUSIONS: Stimulation of the plantar surface of the paw is superior for detecting small changes in paw sensitivity at very low stimulus intensities, whereas stimulation of the dorsal surface is superior for delineating baseline pain thresholds and for detecting robust analgesia. CLINICAL RELEVANCE: Reliable and sensitive assessment of animal pain behaviors is critical to translational pain research. This study demonstrates the importance of using proper test protocols in animal studies and its implication in preclinical screening of potential analgesics.

Insulin is essential for the recovery from allodynia induced by complete Freund's adjuvant.

OBJECTIVE: To determine the effect of streptozotocin (STZ)-induced diabetes on the development and recovery of thermal and mechanical hyperalgesia associated with inflammation induced by subcutaneous injection of complete Freund's adjuvant (CFA). BACKGROUND: The response to nociceptive injury in diabetes differs from that seen in normal individuals in that diabetic patients have increased susceptibility to infections and recover slowly or incompletely from infections and tissue injury due to an abnormal inflammatory response. We have chosen to examine the effect of STZ-induced hypoinsulinemia on the hyperalgesia associated with the enhanced inflammatory state that is induced by the subcutaneous injection of CFA to delineate the potential role of insulin in the development of chronic pain. METHODS: STZ- and vehicle-treated Sprague-Dawley rats were tested using thermal and mechanical stimulation after subcutaneous injection of CFA. The behavioral response was compared with that similarly determined in non-diabetic controls and insulin-depleted rats that received insulin replacement. RESULTS: Recovery of the thermal hyperalgesic response to baseline levels occurred over a period of 9-14 days, but the allodynic response to mechanical stimulation persisted for the duration of the study in STZ-treated rats. Insulin replacement prevented the delay in recovery of mechanical allodynia, but had no obvious effect on nociception in uninflamed tissue. CONCLUSIONS: Normal insulin function is essential for recovery from mechanical allodynia associated with inflammation induced by CFA. Altered insulin metabolism may selectively influence fiber-type specific mechanisms related to mechanical allodynia associated with inflammation and wound healing.

Ranolazine attenuation of CFA-induced mechanical hyperalgesia.

OBJECTIVE: To determine whether ranolazine, a new anti-angina medication, could be an effective analgesic agent in complete Freund's adjuvant-induced inflammatory pain. BACKGROUND: Plantar injection of complete Freund's adjuvant (CFA) produces an extended period of hyperalgesia that is associated with a dramatic up-regulation of Na(v) 1.7 sodium channels in populations of large and small dorsal root ganglion neurons related to the injection site. Ranolazine appears to produce its anti-angina effect through blocking the late sodium current associated with the voltage-gated sodium channel, Na(v) 1.5. Because ranolazine also inhibits Na(v) 1.7, and 1.8, we sought to determine whether it could be an effective analgesic agent in CFA-induced inflammatory pain. METHODS: Baseline determinations of withdrawal from thermal and mechanical stimulation were made in Sprague-Dawley rats ( approximately 300-350 x g). Following determination of baseline, one hindpaw in each group was injected with 0.1 mL of CFA. The contralateral paw received saline. Thermal and mechanical stimulation was repeated on the third day post-injection. Vehicle (0.9% isotonic saline; pH 3.0) or ranolazine was then administered in randomized and blinded doses either by intraperitoneal (ip) injection (0, 10, 20, and 50 mg/kg) or by oral gavage (po; 0, 20, 50, 100, and 200 mg/kg). Animals were again tested 30 minutes (ip) and 1 hour (po) after drug administration. RESULTS: Ranolazine produced dose-dependant analgesia on mechanical allodynia induced by CFA injection, but had no effect on thermal hyperalgesia. CONCLUSIONS: Ranolazine's potential as a new option for managing both angina and chronic inflammatory pain warrants further study.

Ranolazine attenuates behavioral signs of neuropathic pain.

Ranolazine modulates the cardiac voltage-gated sodium channel (NaV 1.5) and is approved by the FDA in the treatment of ischemic heart disease. Ranolazine also targets neuronal (NaV 1.7, 1.8) isoforms that are implicated in neuropathic pain. Therefore, we determined the analgesic efficacy of ranolazine in a preclinical animal model of neuropathic pain. Both intraperitoneal and oral administration of ranolazine dose-dependently inhibited the mechanical and cold allodynia associated with spared nerve injury, without producing ataxia or other behavioral side effects. These data warrant clinical investigation of the potential use of ranolazine in the treatment of neuropathic pain.