Thursday, May 13, 2010

May 2010: Increased Pulmonary Function with Switch to Vaporized Cannabis. (SUNY; Albany, New York)

First some background: When solid particles are burned, they release a variety of molecules as smoke due to the addition of energy in the form of fire. With this addition of energy, a series of chemical reactions occur that release liquid particles and gases that often are of different composition than the original compound. Most often, when an organic compound, such as cannabis, is burned, it emits gases such as carbon monoxide and hydrogen cyanide that may be harmful to the user. Aside from the stigma attached to the name, the potential harmful effects of smoke are one of the main reasons why marijuana is not widely accepted in the medical community. However, there are other ways of administration besides inhaling smoke, such oral or inhaling vapor. Vaporizers heat the cannabis to around 400⁰ F without burning the plant material, reaching the boiling point of most cannabinoids and releasing them in a mist, with not enough heat applied to release other, more harmful compounds.

The new information: In this experiment, twenty frequent cannabis smokers were used to determine the differential effects of inhaling smoke or vapor. The twenty smokers had previously reported at least two respiratory side-effects and were asked to self-report their severity of symptoms. Additionally, their forced expiratory volume (FEV1) and forced vital capacity (FVC) were measured. FEV1 refers to the maximum volume of air that can be exhaled in 1 second, and FVC refers to the total volume of air that the lung can hold. The smokers were then switched to using vaporizers for one month and the measurements were repeated. Initially, average self-reported symptoms were graded to be 26.1, FVC was 4.54L, and FEV1 was 3.22L; after 1 month of vaporizer use, average self-reported symptoms dropped to 6.92, FVC was 4.76L, and FEV1 was 3.6L. The study used 8 males and 4 females (8 of the subjects ended up smoking during the 1 month period) with an average age of 20 years. For these figures, the normal values for FVC and FEV1 should be 4.89 and 4.06L respectively. It should also be noted that approximately a quarter (3) of the subjects also reported tobacco use.

What this means: The results of this experiment indicate that utilizing vaporized cannabis instead of smoke may improve respiratory side-effects and overall pulmonary function. Additionally, this study only represented the improvement after one month of switching to vaporized cannabis, and improvements may increase with an increased time interval. Therefore, utilizing cannabis in vaporized form is significantly safer than smoking it.

Earleywine, M. and Van Dam, N.T. “Pulmonary Function in Cannabis Users: Support for a Clinical Trial of the Vaporizer.” The International Journal on Drug Policy. (2010): preprint.

Monday, May 10, 2010

May 2010: Cannabinoids do not cause oxidative stress as previously thought. (Universidade do Porto; Porto, Portugal)

First some background: In order for human beings to survive, they must consume oxygen. This oxygen consumption drives the most basic of metabolic processes, allowing us to efficiently utilize carbohydrates, proteins, and fats as cellular sources of energy. The final conversion of these molecules to energy occurs within a cellular organelle known as the mitochondria. Within the mitochondria, oxygen is reduced and coupled with hydrogen to produce water, and a resulting hydrogen gradient drives the formation of ATP (cellular energy). However, this process is slightly inefficient, as some of the reduced oxygen fails to couple with hydrogen and become reactive oxygen species, such as superoxide. These reactive oxygen species may cause damage to a cell’s DNA, RNA, or proteins, but are normally converted by a series of enzymes (e.g. superoxide dismutase) into non-reactive molecules. Oxidative stress occurs when the balance between reactive species formation and conversion are disrupted, causing an accumulation of reactive oxygen species and an increase in cellular damage. Reactive oxygen species may also be formed as a byproduct of several other processes such as drug metabolism by cytochrome P450 enzymes. ∆9-Tetrahydrocannabinol (THC) has been previously reported to cause oxidative stress due to an increase in reactive oxygen species formation.1

The new information: In this experiment, mice were injected with either THC, vehicle (the contents of the THC injection without the actual THC), or nothing. The mice livers were then analyzed for the activity level of enzymes that interact with reactive oxygen species: superoxide dismutase, catalase, glutathione-S-transferase, glutathione reductase, and glutathione peroxidase. Additionally, the biomarkers indicating oxidative stress in the mouse liver were lipid peroxidation, protein carbonylation, and DNA oxidation. The results showed that THC caused no change in the activity levels of all 5 enzymes and no biomarkers for oxidative stress were observed. Additionally, the vehicle actually caused an increase in glutathione peroxidase activity, indicating an increase in levels of hydroperoxides, a type of reactive oxygen species. But in the THC injection, the glutathione peroxidase activity level was normal, indicating that THC actually reduced the level of oxidative stress caused by the vehicle.

What this means: This experiment shows that THC in fact does not cause oxidative stress in the liver, and disproves several theories that have been previously presented. This goes to further dispel some of the notions that cannabinoids are more harmful than beneficial for the patient. Additionally, by opposing the increase in glutathione peroxidase activity caused by the vehicle, THC may in fact be an antioxidant in the liver as it has been shown to be in the brain.2 This indicates that cannabinoids may be beneficial in treating other liver diseases besides hepatitis C.

1Sarafian, T.A., et al. “Oxidative Stress Produced by Marijuana Smoke. An Adverse Effect Enhanced by Cannabinoids.” American Journal of Respiratory Cell and Molecular Biology. 20.6(1999): 1286-93.

2Hampson, A.J., et al. “Cannabidiol and (−)Δ9-Tetrahydrocannabinol are Neuroprotective Antioxidants.” Proceedings of the National Academy of Sciences of the United States of America. 95.14(1998): 8268-73.

Pinto, C.E., et al. “Effect of (-)-Delta(9)-Tetrahydrocannabinoid on the Hepatic Redox State of Mice.” Brazilian Journal of Medical and Biological Research. 43.4(2010): 325-9.

Wednesday, May 5, 2010

May 2010: Cannabinoids may be used to target brain cancer cells. (University of the Basque Country; Leioa, Spain)

First some background: Brain cancer refers to the uncontrolled growth of cells in the brain, mainly neurons or glial cells. Glial cells refer to brain cells which do not actually conduct the signals that give rise to bodily function, but rather play a supportive role for neurons. When cancer arises from glial cells, such as oligodendrocytes, astrocytes, microglia, and ependyma, the tumor is referred to as a glioma. Malignant gliomas are the most prominent form of life-threatening brain cancer as well as one of the most aggressive forms of cancer known; thus although gliomas are not the most common, they are one of the most deadly cancers. Additionally, unlike lung or colon cancer, there are no known environmental factors that may cause brain cancer besides vinyl chloride or radiation, which the average person is not readily exposed to; and diagnosing brain cancer involves more expensive imaging techniques. These factors combined make gliomas one of the hardest forms of cancer to battle.

The new information: This experiment aimed to elucidate changes in cannabinoid receptor expression of gliomas. It was conducted by introducing antibodies raised against the receptors to human glial tumors and measuring the rate and levels at which the antibodies bound both cannabinoid receptor 1 and 2 (CB1 and CB2). It was found that in glioblastoma multiforme (the typical glioma), levels of CB1 were decreased by 43% and levels of CB2 were increased by 765% compared to a sample of normal, healthy brain tissue.

What this means: By altering levels of cannabinoid receptors, the brain cancer cells now differentiate themselves in terms of their response to cannabinoids. It has been widely documented that cannabinoids may induce cell apoptosis via CB2 receptors, and thus this astounding increase in CB2 receptor expression by gliomas make them far more susceptible to programmed cell death than other brain cells. Thus, levels of cannabinoids that would be safe for normal brain tissue would cause death in brain cancer cells. Therefore, cannabis may have potential therapeutic effects for those diagnosed with brain cancer, and more specifically, glioblastoma multiforme (GBM).

De Jesús, M.L., et al. “Opposite changes in cannabinoid CB1 and CB2 receptor expression in human gliomas.” Neurochemistry International. 56.6-7(2010): 829-33.

Thursday, April 22, 2010

April 2010: A Mechanism by Which Cannabinoids Act as an Antidepressant is Illustrated. (Charles University; Prague, Czech Republic)

Note: Starting in May, there will consistently be two new summaries a week.

First some background: Mood disorders effect approximately 5-13% of the United States population, with major depressive disorder (unipolar depression) reflecting 4-9%.* Although the etiology of depression is not well understood, it is associated with decreased hippocampal volume. Within the hippocampus, a region named the subgranular zone is one of only two areas in the brain where new brain cells can be produced. This area of the hippocampus contains stem cells that form new neurons and differentiate in response to brain-derived neurotrophic factor (BDNF). Antidepressants work by increasing levels of serotonin, dopamine, and norepinephrine in the brain. Increased levels of serotonin and norepinephrine cause an increase in BDNF levels, thus causing an increase in hippocampal volume. Current pharmacological mechanisms for treating depression utilize reuptake inhibitors, which increase levels of these chemicals by inhibiting their reuptake into brain cells. However, older antidepressants, less favored now because of their side effects, are targeted to inhibit the enzyme monoamine oxidase (e.g. isocarboxazid, phelezine). Monoamines refer to a class of molecules which include the aforementioned neurotransmitters serotonin, dopamine, and norepinephrine as well as several others such as histamine. The enzyme monoamine oxidase catalyzes the degradation of these monoamines, thus a monoamine oxidase inhibitor (MAOI) would cause higher levels of these chemicals in the brain. There are two types of monoamine oxidase enzymes found in the human body, MAO-A and MAO-B. MAO-A is found mainly in brain cells that utilize norepinephrine and is able to degrade norepinephrine, serotonin, and dopamine most effectively; while MAO-B is found mainly in brain cells that utilize serotonin and is able to degrade β-phenylethanolamine and dopamine most effectively.

The new information: This experiment tested the effect of three cannabinoids on the activity of both monoamine oxidase enzymes. The three cannabinoids used were ∆9-tetrahydrocannabinol (THC), anandamide (a cannabinoid that occurs naturally in our body), and the synthetic cannabinoid WIN (WIN 55,212-2). The concentrations needed to inhibit 50% of the enzyme activity were then compared with the MAOI medication iproniazid. It was found that the MAO-A enzyme was blocked at lowest concentrations by WIN, followed closely by THC, with a large gap in concentration between THC and anandamide. The MAO-B enzyme was blocked at approximately equal concentrations of THC and WIN, with a large gap in concentrations between them and anandamide. Additionally, the concentrations at which all three blocked the MAOs were much greater than the concentration of iproniazid needed for the same result. The concentrations were measured in micromoles per liter, meaning that they were measured based on number of molecules and not their size or weight.

What this means: The results of this experiment illustrate in detail the dependence of the antidepressant effect of cannabis on concentration of cannabinoids. Because the effect of THC on monoamine oxidase is not as powerful as MAOI medications, there will not be the dangerous drug and food interactions that are notorious side effects of MAOIs. However, marijuana would nonetheless increase the amount of serotonin and norepinephrine in the brain, thus leading to an expansion in the size of the hippocampus. This neurogenerative effect is part of what leads to the antidepressant properties of marijuana. Additionally, damage to the hippocampus is also seen in Alzheimer’s disease, decreases in long-term memory, post-traumatic stress disorder, schizophrenia, and epilepsy caused by hippocampal sclerosis. Thus cannabis may hypothetically be helpful in the treatment of these conditions and more through its action as an inhibitor of the enzyme monoamine oxidase.

*Nestler, E.J., Hyman, S.E., and Malenka, R.C. Molecular Neuropharmacology: A Foundation for Clinical Neuroscience. New York: McGraw-Hill, 2009.

Fišar, Z. “Inhibition of Monoamine Oxidase Activity by Cannabinoids.” Naunyn-Schmiedeberg’s Archives of Pharmacology. (2010): preprint.

Sunday, April 11, 2010

June 2010: Cannabinoids inhibit a group of cancer-causing enzymes. (Hokuriku University; Kanazawa, Japan)

Note: June refers to the publication date

First some background: The human body contains an expansive number of enzymes, proteins which increase the rate of chemical reactions in our bodies. These enzymes typically facilitate the various molecular metabolic processes that are occurring at any given second within our cells, but some of their products and/or byproducts can be harmful, even carcinogenic (cause cancer). Perhaps the largest group of enzymes in our bodies is the cytochrome P450 (CYP) family, which catalyze the monooxidation (addition of one oxygen) of various organic molecules. One of the main functions of this enzyme family is the metabolism of drugs in the liver. However, some subfamilies, such as the CYP1 subfamily (enzymes CYP1A1, CYP1A2, CYP1B1), also induce the formation of carcinogenic compounds from polycyclic aromatic hydrocarbons. Polycyclic aromatic hydrocarbons are common constituents of smoke, especially cigarette smoke, and are known as procarcinogens. The label procarcinogen indicates that the molecule in and of itself will not cause cancer, but can be induced to cause cancer when altered by a metabolic process.

The new information: This experiment tested the effects of three cannabinoids found in marijuana on the catalytic effects of CYP1 enzymes. The three cannabinoids used were delta(9)-tetrahydrocannabinol (THC), cannabidiol, and cannabinol; it was found that all three cannabinoids inhibited all three CYP1 enzymes to some degree, with THC being the least potent inhibitor, cannabidiol inhibiting CYP1A1 most effectively, and cannabinol inhibiting CYP1A2 and CYP1B1 most effectively. Additionally, it was shown that all three cannabinoids were competitive inhibitors, meaning that at higher concentrations/potencies of other substrates for the CYP1 enzymes, the cannabinoids were displaced.

What this means: By illustrating that three of the major cannabinoids found in marijuana can cause potent inhibition of all three enzymes in the CYP1 subfamily, marijuana may prevent certain forms of cancer. Polycyclic aromatic hydrocarbons are common components in environmental pollution, and are usually inhaled, resulting in lung cancer. By inhibiting the enzyme that converts the procarcinogen into the cancer-causing compound, cannabis may be prophylactically used to prevent one of the main causes of lung cancer. Additionally, because CYP1 enzymes are also involved in drug metabolism, cannabis could be use to augment various pharmaceuticals for maximal effectiveness. In order for a drug to be excreted from the body, it generally first passes through at least two phases of metabolism, with cytochrome P450 enzymes representing one of the major components of the first phase. Thus if a drug is known to be metabolized by one of the CYP1 enzymes and cannabis is co-administered, it would take longer for the drug to be broken down in and removed from our bodies. Therefore, cannabis could extend the half-life of various medications, possibly reducing the cost to patients.

Yamaori, S., et al. “Characterization of Major Phytocannabinoids, Cannabidiol and Cannabinol, as Isoform-selective and Potent Inhibitors of Human CYP1 Enzymes.” Biochemical Pharmacology. 79.11(2010): 1691-8.

Tuesday, April 6, 2010

March 2010: Cannabinoids inhibit and may prevent neuropathic pain in diabetes. (University of Calgary; Alberta, Canada)

First some background: According to the World Health Organization, more than 220 million people worldwide are living with diabetes. Within the United States, the National Diabetes Fact Sheet cites 23.6 million people, or 7.6% of the population, as currently living with diabetes; and an additional 1.6 million as diagnosed each year. There are two common forms of diabetes: type I and type II. Type I diabetes usually affects an individual at birth, as they are unable to produce insulin in sufficient quantity. Type II diabetes typically occurs later in an individual's life and reflects a decreased ability of cells to utilize insulin. Insulin is a hormone secreted from Beta cells of the pancreas mainly in response to increased glucose levels in the blood. Insulin acts to allow glucose to be taken up by cells in muscle, liver, and fat, and subsequently being converted into stored forms of energy. With the accompanying lack of insulin or its function in diabetes, glucose, the simplest form of sugar, accumulates in the bloodstream, leading to a multitude of pathologies including neuropathic pain. Hyperglycemia (elevated blood glucose) causes small blood vessels to uptake higher levels of glucose, leading to thicker as well as weaker blood vessel membranes. With these thicker blood vessels comes a reciprocal decrease in blood flow, leading to decreased oxygen levels in many organs, including the brain. The decreased oxygen levels in the brain decreases the conduction velocity of neurons and may cause structural changes in brain cells. Additionally, Hyperglycemia causes the upregulation of oxygen radicals as well as the activation of microglia, both of which can damage nerve cells. Microglia are a type of brain cell that act as immune cells of the brain, they respond to infections of the brain and spinal cord. However, their activation in diabetes causes them to release cytotoxic chemicals in absence of infection, which can damage nerve cells. This damage and structural change in nerve cells is thought to be responsible for the phenomenon of diabetic peripheral neuropathy. It has been previously shown that inhibiting microglial activation leads to a dissipation of neuropathic pain in mouse models of diabetes.* It is also well known that both neurons and microglial cells express cannabinoid receptors.

The new information: This experiment involved inducing diabetes in mice in the presence and absence of cannabinoid agonists and observing the mice over a course of 8 months. There were six main experimental groups, one of which diabetes was induced without cannabinoid treatment, serving as a control. In a second group, diabetes was induced in conjunction with cannabidiol treatment. It was found that in this second group, neuropathic pain did not develop over the course of 8 months and the levels of activated microglia in the spinal cord were greatly reduced compared to the control. Additionally, when cannabidiol treatment was stopped, the mice continued to show reduced microglia as well as no signs of neuropathic pain. A third and fourth group involved the induction of diabetes and treatment with both CB1 and CB2 cannabinoid receptor agonists once symptoms of neuropathic pain started. The results indicated that both CB1 and CB2 agonists inhibited the symptoms of neuropathic pain, but the pain returned after treatment was stopped. The last two groups involved treatment with CB1 and CB2 cannabinoid receptor antagonists, which block the effect of cannabinoids, and no change was seen in the levels of pain compared to the control group.

What this means: This experiment provided more evidence that cannabinoids may be used in the treatment of neuropathic pain. However, the novel information obtained is much more surprising. When treated with cannabidiol at the onset of diabetes, the diabetic mice did not have any symptoms of neuropathic pain even when treatment was stopped. This suggests that treatment with cannabidiol at the onset of diabetes may produce permanent protective changes for nerve cells. Therefore, cannabis could hypothetically be used short-term at the onset of type II diabetes in adults for lifetime or long-term prevention of diabetic peripheral neuropathy.

*Tsuda, M., et al. “Activation of Dorsal Horn Microglia Contributes to Diabetes-induced Tactile Allodynia via Extracellular Signal-regulated Protein Kinase Signaling.” Glia. 56.4(2008): 378-86.

Toth, C., et al. “Cannabinoid-mediated Modulation of Neuropathic Pain and Microglial Accumulation in a Model of Murine Type I Diabetic Peripheral Neuropathic Pain.” Molecular Pain. 6.16(2010).

Monday, March 29, 2010

March 2010: A novel process by which cannabinoids alleviate pain has been determined molecularly (Medizinische Hochschule Hannover; Hannover, Germany)

First some background: Chronic pain is often a difficult condition to treat and sometimes even diagnose. Originating as a protective mechanism, pain notifies us when an external stimulus may cause us harm or when something internal start to go awry. However, in certain types of chronic pain and what is referred to as neuropathic pain, this once protective mechanism exhibits functional degeneracy, where its function in the human body is not established. What has been well established however, is the process by which we feel this pain. When peripheral cells are damaged, an inflammatory response ensues, leading to the release of chemicals such as bradykinin, histamine, prostanoids, and tachykinins. These chemicals as well as physical pressure and severe temperatures act on dendritic terminals of nociceptive neurons, mostly activating TRP (transient receptor potential) channels. These TRP channels are a family of stimulus-sensitive non-selective cation channels, thus permeable to sodium, calcium, magnesium, and other positively charged ions. Activation of TRP channels causes a signal to be sent along this nociceptive (pain) neuron, whose cell body resides in the dorsal root ganglion. These cell bodies then relay their signal to a different neuron in the spinal cord. This spinal cord neuron, located in the dorsal horn, also receives input from several other neurons, dictating the level of pain felt and are usually inhibitory. It is well documented that cannabinoids can act in a retrograde fashion at these synapses utilizing CB1 (cannabinoid receptor 1) in order to inhibit the signal coming from the primary afferent neuron (the one that originally sensed the pain). Additionally, it has been established that cannabinoids may act at TRP channels directly, desensitizing them to painful stimuli. However, in recent years, it has emerged that cannabinoids may also act on other parts of the pain pathway.

The new information: Although it has been previously noted that cannabinoids act on different parts of the pain pathway, including glycine receptors, the exact molecular mechanism has not been established. The modulatory inhibitory neurons utilize one of two neurotransmitters to decrease the painful signal coming from the primary afferent neuron: GABA (gamma-aminobutyric acid) and glycine. It is known that cannabinoids somehow act on glycine receptors in order to decrease the sensation of pain. This experiment involved mutating the glycine receptor in specific regions to determine how cannabinoids, specifically cannabidiol, interact with the receptor. By mutating an amino acid in the second transmembrane domain from serine (polar) to isoleucine (nonpolar), cannabidiol had no effect on the receptor. However, in absence of the mutation, cannabidiol caused both co-activation and direct activation of the glycine receptor. Co-activation is also referred to as positive allosteric modulation, where the cannabinoid by itself will not activate the receptor, but in presence of glycine (the receptor agonist), there is an increased intracellular response. Additionally, cannabidiol was shown to directly activate this receptor, causing inhibition of the noxious (painful) signal.

What this means: As mentioned in previous entries, THC (∆9-tetrahydrocannabinol) is not the only cannabinoid found in plants of the Cannabis genus. The remaining cannabinoids all have differing structures, properties, and functions. However, the current pharmaceutical market utilizes only THC containing medication, which cannot fully utilize the benefits of Marijuana. By showing the exact molecular mechanism by which cannabidiol interacts with glycine receptors, another means by which cannabis lead to analgesia has been established.

Foadi, N., et al. “Lack of Positive Allosteric Modulation of Mutated Alpha(1)S267I Glycine Receptors by Cannabinoids.” Naunyn-Schmiedeberg's Archives of Pharmacology. (2010): preprint.