Chronic Exposure to Tramadol Induces Neurodegeneration in the Cerebellum of Adult Male Rats

Tramadol use and incident dementia in older adults with musculoskeletal pain: a population-based retrospective cohort study

We aimed to assess the association of tramadol use with the risk of dementia. This population-based retrospective cohort study using the Korean National Health Insurance Service database included a total of 1,865,827 older adult patients aged 60 years or older with common musculoskeletal pain between January 1, 2003, and December 31, 2007. Individuals who were newly dispensed tramadol (N = 41,963) were identified and propensity score-matched with those who were not (N = 41,963). Over a maximum of 14-year follow-up, the incidence rates (events per 1000 person-years) of all-cause dementia were 6.1 for nonusers, 6.2 for those with cumulative tramadol use of 1-14 days, 7.7 for those with 15-90 days of use, and 8.0 for those with > 90 days of use. Longer cumulative duration of tramadol use was associated with an increased risk of all-cause dementia compared with nonuse (1 to 14 days: aHR 1.06, 95% CI 0.96-1.17; 15 to 90 days: aHR 1.14, 95% CI 1.10-1.35; and more than 90 days: aHR 1.18, 95% CI 1.00-1.39; test for trend: P < 0.001). The results showed a similar pattern for Alzheimer's disease and were robust across subgroup and sensitivity analyses, but not for vascular dementia. This study found that exposure to tramadol was associated with an increased risk of dementia. Taking this potential risk into consideration, clinicians should carefully weigh potential benefits and risks when prescribing tramadol to older adults with musculoskeletal pain.

Does Tramadol Exposure Have Unfavorable Effects on Hippocampus? A Review Study

Background

Tramadol, one of the most common opioid pain relievers, acts upon the µ-receptor in the central nervous system (CNS) to alleviate pain associated with various situations like postoperative pain, arthritis, and muscular pain. Additionally, it has been utilized to address depression and anxiety disorders. Extensive research has shown that tramadol can potentially inflict irreversible harm on different regions of the CNS, including the cerebrum, cerebellum, amygdala, and, notably, the hippocampal formation. However, the precise mechanism behind these effects remains unclear. Within this study, we conducted a comprehensive examination of the impacts of tramadol on the CNS, specifically focusing on hippocampal formation.

Methods

In this study, we collected relevant articles published between 2000 and 2022 by conducting searches using specific keywords, including tramadol, tramadol hydrochloride, central nervous system, hippocampus, and hippocampal formation, in various databases.

Findings

The results of this study proposed several processes by which tramadol may impact the CNS, including the induction of apoptosis, autophagy, excessive production of free radicals, and dysfunction of cellular organelles. These processes ultimately lead to disturbances in neural cell function, particularly within the hippocampus. Furthermore, it is revealed that tramadol administration led to a significant decrease in the neural cell count and the volume of various regions within the brain and spinal cord.

Conclusion

Consequently, neuropsychological impairments, such as memory formation, attention deficits, and cognitive impairment, may happen. This finding highlights the potential impacts of tramadol on neural structures and warrants further investigation.

Unraveling the Hippocampal Molecular and Cellular Alterations behind Tramadol and Tapentadol Neurobehavioral Toxicity

Tramadol and tapentadol are chemically related opioids prescribed for the analgesia of moderate to severe pain. Although safer than classical opioids, they are associated with neurotoxicity and behavioral dysfunction, which arise as a concern, considering their central action and growing misuse and abuse. The hippocampal formation is known to participate in memory and learning processes and has been documented to contribute to opioid dependence. Accordingly, the present study assessed molecular and cellular alterations in the hippocampal formation of Wistar rats intraperitoneally administered with 50 mg/kg tramadol or tapentadol for eight alternate days. Alterations were found in serum hydrogen peroxide, cysteine, homocysteine, and dopamine concentrations upon exposure to one or both opioids, as well as in hippocampal 8-hydroxydeoxyguanosine and gene expression levels of a panel of neurotoxicity, neuroinflammation, and neuromodulation biomarkers, assessed through quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemical analysis of hippocampal formation sections showed increased glial fibrillary acidic protein (GFAP) and decreased cluster of differentiation 11b (CD11b) protein expression, suggesting opioid-induced astrogliosis and microgliosis. Collectively, the results emphasize the hippocampal neuromodulator effects of tramadol and tapentadol, with potential behavioral implications, underlining the need to prescribe and use both opioids cautiously.

Evaluation of histological and ultrastructural changes provoked by prenatal tramadol on postnatal cortical cerebellar neuronal development in rats: possible implication of Ki67, GFAP and MicroRNA-7/P53 signalling trajectories

Tramadol is a novel centrally acting analgesic. Despite, its implementation during pregnancy may impair neuronal survival and synaptic development in neonatal cerebella. The current investigation assessed the histological and ultrastructural alterations in postnatal cortical cerebellar neuronal development induced by prenatal tramadol. 30 offsprings were divided to control group I: fifteen pups born to mothers given saline from D10 till D21 of gestation. Tramadol-treated group II: fifteen pups born to mothers received tramadol HCL (50 mg/kg/day) from D10 till D21 of gestation. Pups were categorized into three subgroups (a, b, and c) and offered for sacrifice on the seventh, fourteenth and twenty-first post-natal days. Light microscopic examination revealed the overcrowding and signs of red degeneration affecting purkinje cell layer. Neurodegenerative signs of both purkinje and granule cell neurons were also confirmed by TEM in form of chromatin condensation, dilated Golgi channels, disrupted endoplasmic reticulum, marked infolding of the nuclear envelope and decrease in granule cell precursors. In addition, the astrocytic processes and terminal nerve axons appeared with different degrees of demyelination and decreased number of oligodendrocytes and degenerated mitochondria. Furthermore, group II exhibited an increase in P53 immune expression. The area percentage of apoptotic cells detected by TUNEL assay was significantly increased. Besides to the significant decrease of Ki67 immunoreactivity in the stem neuronal cell progenitors. Quantitative PCR results showed a significant decline in micro RNA7 gene expression in tramadol treated groups resulting in affection of multiple target genes in P53 signaling pathways, improper cortical size and defect in neuronal development.

Coenzyme Q10 attenuates neurodegeneration in the cerebellum induced by chronic exposure to tramadol

BACKGROUND

Chronic use of tramadol can cause neurotoxic effects and subsequently cause neurodegeneration in the cerebellum. The main damage mechanisms identified are oxidative stress and inflammation. Currently, we investigated the effects of coenzyme Q10 (CoQ10) in attenuates of neurodegeneration in the cerebellum induced by chronic exposure to tramadol.

MATERIAL AND METHODS

Seventy-two male mature albino rats were allocated into four equal groups, including; non-treated group, CoQ10 group (which received CoQ10 at 200 mg/kg/day orally for three weeks), tramadol group (which received tramadol hydrochloride at 50 mg/kg/day orally for three weeks), and tramadol+CoQ10 group (which received tramadol and CoQ10 at the same doses as the previous groups). Tissue samples were obtained for stereological, immunohistochemical, biochemical, and molecular evaluations. Also, functional tests were performed to evaluate behavioral properties.

RESULTS

We found a significant increase in stereological parameters, antioxidant factors (catalase, glutathione, and superoxide dismutase), and behavioral function scores in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05). In addition, malondialdehyde levels, the density of apoptotic cells, as well as the expression of pro-inflammatory (tumor necrosis factor-alpha, interleukin 1 beta, and interleukin 6) and autophagy (lysosome-associated membrane protein 2, autophagy-related 5, beclin 1, and autophagy-related 12) genes were considerably reduced in the tramadol+CoQ10 group compared to the tramadol group (p < 0.05).

CONCLUSION

We conclude that the administration of CoQ10 has neuroprotective effects in the cerebellum of rats that have chronic exposure to tramadol.

Tramadol induces apoptosis, inflammation, and oxidative stress in rat choroid plexus

BACKGROUND

The choroid plexus (CP) is the principal source of cerebrospinal fluid (CSF). It can produce and release a wide range of materials, including growth and neurotrophic factors which have a crucial role in the maintenance and proper functioning of the brain. Tramadol is a synthetic analog of codeine, mainly prescribed to alleviate mild to moderate pains. Nevertheless, it causes several side effects, such as emotional instability and anxiety.

METHODS

In this study, we focused on alterations in the expression of inflammatory and apoptotic genes in the CP under chronic tramadol exposure. Herein, rats were treated daily with tramadol at 50 mg/kg doses for three weeks. CSF samples were collected, with superoxide dismutase (SOD) and glutathione (GSH) measured in the CSF.

RESULTS

We found that tramadol reduced the SOD and GSH levels in the CSF. Furthermore, the stereological analysis revealed a significant increase in the CP volume, epithelial cells, and capillary number upon tramadol administration. Tramadol elevated the number of blob mitochondria in CP. Also, we observed the upregulation of inflammatory and apoptosis genes following tramadol administration in the CP.

CONCLUSIONS

Our findings indicate that tramadol induces neurotoxicity in the CP via apoptosis, inflammation, and oxidative stress.

Exposure to Δ9-tetrahydrocannabinol leads to a rise in caspase-3, morphological changes in microglial, and astrocyte reactivity in the cerebellum of rats

The present study aimed to elucidate the effect of 10 mg/kg Δ9-tetrahydrocannabinol (THC) on cerebellar neuronal and glial morphology, apoptosis and inflammatory gene expression using a series of histological assays including stereology, Sholl analysis, immunofluorescence and real-time qPCR in male Wistar rats. A decrease in the number of Purkinje neurons and the thickness of the granular layer in the cerebellum was reported in THC-treated rats. Increased expression of Iba-1 and arborization of microglial processes were evidence of microgliosis and morphological changes in microglia. In addition, astrogliosis and changes in astrocyte morphology were other findings associated with THC administration. THC also led to an increase in caspase-3 positive cells and a decrease in autophagy and inflammatory gene expression such as mTOR, BECN1 and LAMP2. However, there were no significant changes in the volume of molecular layers and white matter, the spatial arrangement of granular layers and white matter, or the spatial arrangement of granular layers and white matter in the cerebellum. Taken together, our data showed both neuroprotective and neurodegenerative properties of THC in the cerebellum, which require further study in the future.

Role of apoptosis and autophagy in mediating tramadol-induced neurodegeneration in the rat hippocampus

BACKGROUND

Tramadol (TRA) is an analgesic prescribed for treating mild to moderate pains, the abuse of which has increased in recent years. Chronic tramadol consumption produces neurotoxicity, although the mechanisms are unclear. The present study investigated the involvement of apoptosis and autophagy signaling pathways and the mitochondrial system in TRA-induced neurotoxicity.

MATERIALS AND METHODS

Sixty adult male Wistar rats were divided into five groups that received standard saline or TRA in doses of 25, 50, 75, 100, or 150 mg/kg intraperitoneally for 21 days. On the 22nd day, the Open Field Test (OFT) was conducted. Jun N-Terminal Kinase (JNK), B-cell lymphoma-2 (Bcl-2), Beclin1, and Bcl-2-like protein 4 (Bax) proteins and tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) were measured in rat hippocampal tissue.

RESULTS

TRA at doses 75, 100, and 150 mg/kg caused locomotor dysfunction in rats and increased total and phosphorylated forms of JNK and Beclin-1, Bax, and Caspase-3. TRA at the three higher doses also increased the phosphorylated (inactive) form of Bcl-2 level while decreasing the unphosphorylated (active) form of Bcl-2. Similarly, the protein levels of TNF-α and IL-1β were increased dose-dependently. The mitochondrial respiratory chain enzymes were reduced at the three higher doses of TRA.

CONCLUSION

TRA activated apoptosis and autophagy via modulation of TNF-α or IL-1β/JNK/Bcl-2/Beclin1 and Bcl-2/Bax signaling pathways and dysfunction of mitochondrial respiratory chain enzymes.

Effect of tramadol on apoptosis and synaptogenesis in hippocampal neurons: The possible role of µ-opioid receptor

Tramadol is a synthetic opioid with centrally acting analgesic activity that alleviates moderate to severe pain and treats withdrawal symptoms of the other opioids. Like other opioid drugs, tramadol abuse has adverse effects on central nervous system components. Chronic administration of tramadol induces maladaptive plasticity in brain structures responsible for cognitive function, such as the hippocampus. However, the mechanisms by which tramadol induces these alternations are not entirely understood. Here, we examine the effect of tramadol on apoptosis and synaptogenesis of hippocampal neuronal in vitro. First, the primary culture of hippocampal neurons from neonatal rats was established, and the purity of the neuronal cells was verified by immunofluorescent staining. To evaluate the effect of tramadol on neuronal cell viability MTT assay was carried out. The western blot analysis technique was performed for the assessment of apoptosis and synaptogenesis markers. Results show that chronic exposure to tramadol reduces cell viability of neuronal cells and naloxone reverses this effect. Also, the level of caspase-3 significantly increased in tramadol-exposed hippocampal neurons. Moreover, tramadol downregulates protein levels of synaptophysin and stathmin as synaptogenesis markers. Interestingly, the effects of tramadol were abrogated by naloxone treatment. These findings suggest that tramadol can induce neurotoxicity in hippocampal neuronal cells, and this effect was partly mediated through opioid receptors.