Pravastatin protection from cold stress in myocardium of rats

Unraveling the Mystery of Cold Stress-Induced Myocardial Injury

Exposure to low ambient temperature imposes great challenge to human health. Epidemiological evidence has noted significantly elevated emergency admission and mortality rate in cold climate in many regions, in particular, adverse events in cardiovascular system. Cold stress is becoming one of the important risk factors for cardiovascular death. Through recent advance in echocardiography and myocardial histological techniques, both clinical and experimental experiments have unveiled that cold stress triggers a variety of pathological and pathophysiological injuries, including ventricular wall thickening, cardiac hypertrophy, elevated blood pressure, decreased cardiac function, and myocardial interstitial fibrosis. In order to examine the potential mechanism of action behind cold stress-induced cardiovascular anomalies, ample biochemical and molecular biological experiments have been conducted to denote a role for mitochondrial injury, intracellular Ca²⁺ dysregulation, generation of reactive oxygen species (ROS) and other superoxide, altered gene and protein profiles for apoptosis and autophagy, and increased adrenergic receptor sensitivity in cold stress-induced cardiovascular anomalies. These findings suggest that cold stress may damage the myocardium through mitochondrial injury, apoptosis, autophagy, metabolism, oxidative stress, and neuroendocrine pathways. Although the precise nature remains elusive for cold stress-induced cardiovascular dysfunction, endothelin (ET-_A) receptor, endoplasmic reticulum (ER) stress, transient receptor potential vanilloid, mitochondrial-related protein including NRFs and UCP-2, ROS, Nrf2-Keap1 signaling pathway, Bcl-2/Bax, and lipoprotein lipase (LPL) signaling may all play a pivotal role. For myocardial injury evoked by cold stress, more comprehensive and in-depth mechanisms are warranted to better define the potential therapeutic options for cold stress-associated cardiovascular diseases.

Evaluation of cebranopadol, a dually acting nociceptin/orphanin FQ and opioid receptor agonist in mouse models of acute, tonic, and chemotherapy-induced neuropathic pain

BACKGROUND

Cebranopadol (a.k.a. GRT-6005) is a dually acting nociceptin/orphanin FQ and opioid receptor agonist that has been recently developed in Phase 2 clinical trials for painful diabetic neuropathy or cancer pain. It also showed analgesic properties in various rat models of pain and had a better safety profile as compared to equi-analgesic doses of morphine. Since antinociceptive properties of cebranopadol have been studied mainly in rat models, in the present study, we assessed analgesic activity of subcutaneous cebranopadol (10 mg/kg) in various mouse pain models.

METHODS

We used models of acute, tonic, and chronic pain induced by thermal and chemical stimuli, with a particular emphasis on pharmacoresistant chronic neuropathic pain evoked by oxaliplatin in which cebranopadol was used alone or in combination with simvastatin.

KEY RESULTS

As shown in the hot plate test, the analgesic activity of cebranopadol developed more slowly as compared to morphine (90-120 min vs. 60 min). Cebranopadol displayed a significant antinociceptive activity in acute pain models, i.e., the hot plate, writhing, and capsaicin tests. It attenuated nocifensive responses in both phases of the formalin test and reduced cold allodynia in oxaliplatin-induced neuropathic pain model. Its efficacy was similar to that of morphine. Used in combination and administered simultaneously, 4 or 6 h after simvastatin, cebranopadol did not potentiate antiallodynic activity of this cholesterol-lowering drug. Cebranopadol did not induce any motor deficits in the rotarod test.

CONCLUSION

Cebranopadol may have significant potential for the treatment of various pain types, including inflammatory and chemotherapy-induced neuropathic pain.

Memantine effects on liver and adrenal gland of rats exposed to cold stress

Background

Memantine attenuates heart stress due cold stress, however, no study focused its effects on liver and adrenal gland. We evaluated its effects on lipid depletion in adrenal gland and glycogen depletion in liver of rats exposed to cold stress.

Methods

Male rats divided into 4 groups: 1)Control (CON); 2)Memantine (MEM); 3)Induced cold stress (IH) and; 4)Induced cold stress memantine (IHF). Memantine were administrated by gavage (20 mg/kg/day) during eight days. Cold stress were performed during 4 hours once at - 8°C. Lipid and glycogen depletion were presented as its intensity levels.

Results

Rats exposed to cold stress presented the highest glycogen (p < 0.001) and lipid depletion (p < 0.001) in liver and adrenal gland, respectively. We noted that memantine significantly reduced lipid depletion in adrenal gland and glycogen depletion in liver.

Conclusion

Memantine prevented glycogen depletion in liver and lipid depletion in adrenal gland of rats under a cold stress condition.

Electric countershock and cold stress effects on liver and adrenal gland

OBJECTIVES

Cold exposure induces glycogen and lipid depletion in the liver and the adrenal gland, respectively. However, no previous study has determined the effects of electrical countershock on those tissues. We aimed to evaluate the effects of electrical countershock on lipid depletion in the adrenal gland and on glycogen depletion in the liver.

METHODS

We used 40 male Wistar rats divided into four groups: the control group, in which the animals were subjected to a resting period of seven days; the electrical discharge group, in which the animals were subjected to a resting period followed by administration of ten 300-mV electrical discharges; the electrical post-discharge group, in which the animals received ten electrical shocks (300 mV) followed by rest for seven consecutive days; and the cold stress group, in which the animals were subjected to a resting period and were then exposed to -8 degrees C temperatures for four hours. All animals underwent a laparotomy after treatment. The lipid and glycogen depletions are presented using intensity levels (where + = low intensity and ++++ = high intensity, with intermediate levels in between).

RESULTS

The rats exposed to the cold stress presented the highest glycogen and lipid depletion in the liver and the adrenal gland, respectively. Furthermore, we noted that the electrical countershock significantly increased lipid depletion in the adrenal gland and glycogen depletion in the liver. One week after the electrical countershock, the liver and adrenal gland profiles were similar to that of the control group.

CONCLUSION

Electrical countershock immediately increased the glycogen depletion in the liver and the lipid depletion in the adrenal gland of rats.

Memantine prevents cardiomyocytes nuclear size reduction in the left ventricle of rats exposed to cold stress

OBJECTIVES

Memantine is an N-methyl-d-aspartate (NMDA) glutamate receptor antagonist used to treat Alzheimer's disease. Previous studies have suggested that receptor blockers act as neuroprotective agents; however, no study has specifically investigated the impact that these drugs have on the heart. We sought to evaluate the effects of memantine on nuclear size reduction in cardiac cells exposed to cold stress.

METHOD

We used male EPM-Wistar rats (n=40) divided into 4 groups: 1) Matched control (CON); 2) Memantine-treated rats (MEM); 3) Rats undergoing induced hypothermia (IH) and 4) Rats undergoing induced hypothermia that were also treated with memantine (IHM). Animals in the MEM and IHM groups were treated by oral gavage administration of 20 mg/kg/day memantine over an eight-day period. Animals in the IH and IHM groups were submitted to 4 hours of hypothermia in a controlled environment with a temperature of -8 degrees C on the last day of the study.

RESULTS

The MEM group had the largest cardiomyocyte nuclear size (151 +/- 3.5 microm(3) vs. CON: 142 +/- 2.3 microm(3); p<0.05), while the IH group had the smallest mean value of nuclear size. The nuclear size of the IHM group was preserved (125 +/- 2.9 microm(3)) compared to the IH group (108 +/- 1.7 microm(3); p<0.05).

CONCLUSION

Memantine prevented the nuclear size reduction of cardiomyocytes in rats exposed to cold stress.