Melatonin attenuates inflammatory response‐induced brain edema in early brain injury following a subarachnoid hemorrhage: a possible role for the regulation of pro‐inflammatory cytokines

Melatonin is a strong anti‐oxidant that has beneficial effects against early brain injury (EBI) following a subarachnoid hemorrhage (SAH) in rats; protection includes the reduction of both mortality and neurological deficits. The molecular mechanisms underlying these clinical effects in the SAH model have not been clearly identified. This study examined the influence of melatonin on brain edema secondary to disruption of the blood–brain barrier (BBB) and the relationship between these effects and pro‐inflammatory cytokines in EBI following SAH using the filament perforation model of SAH in male Sprague–Dawley rats. Melatonin (150 mg/kg) or vehicle was given via an intraperitoneal injection 2 hr after SAH induction. Brain samples were extracted 24 hr after SAH. Melatonin treatment markedly attenuated brain edema secondary to BBB dysfunctions by preventing the disruption of tight junction protein expression (ZO‐1, occludin, and claudin‐5). Melatonin treatment also repressed cortical levels of pro‐inflammatory cytokines (IL‐1β, IL‐6, and TNF‐α), which were increased in EBI 24 hr after SAH. To further identify the mechanism of this protection, we demonstrated that administration of melatonin attenuated matrix metallopeptidase 9 expression/activity and vascular endothelial growth factor expression, which are related to the inflammatory response and BBB disruption in EBI after SAH. Taken together, this report shows that melatonin prevents disruption of tight junction proteins which might play a role in attenuating brain edema secondary to BBB dysfunctions by repressing the inflammatory response in EBI after SAH, possibly associated with regulation of pro‐inflammatory cytokines.     

Melatonin attenuates myocardial ischemia‐reperfusion injury via improving mitochondrial fusion/mitophagy and activating the AMPK‐OPA1 signaling pathways

Optic atrophy 1 (OPA1)‐related mitochondrial fusion and mitophagy are vital to sustain mitochondrial homeostasis under stress conditions. However, no study has confirmed whether OPA1‐related mitochondrial fusion/mitophagy is activated by melatonin and, consequently, attenuates cardiomyocyte death and mitochondrial stress in the setting of cardiac ischemia‐reperfusion (I/R) injury. Our results indicated that OPA1, mitochondrial fusion, and mitophagy were significantly repressed by I/R injury, accompanied by infarction area expansion, heart dysfunction, myocardial inflammation, and cardiomyocyte oxidative stress. However, melatonin treatment maintained myocardial function and cardiomyocyte viability, and these effects were highly dependent on OPA1‐related mitochondrial fusion/mitophagy. At the molecular level, OPA1‐related mitochondrial fusion/mitophagy, which was normalized by melatonin, substantially rectified the excessive mitochondrial fission, promoted mitochondria energy metabolism, sustained mitochondrial function, and blocked cardiomyocyte caspase‐9‐involved mitochondrial apoptosis. However, genetic approaches with a cardiac‐specific knockout of OPA1 abolished the beneficial effects of melatonin on cardiomyocyte survival and mitochondrial homeostasis in vivo and in vitro. Furthermore, we demonstrated that melatonin affected OPA1 stabilization via the AMPK signaling pathway and that blockade of AMPK repressed OPA1 expression and compromised the cardioprotective action of melatonin. Overall, our results confirm that OPA1‐related mitochondrial fusion/mitophagy is actually modulated by melatonin in the setting of cardiac I/R injury. Moreover, manipulation of the AMPK‐OPA1‐mitochondrial fusion/mitophagy axis via melatonin may be a novel therapeutic approach to reduce cardiac I/R injury.     

Melatonin alleviates secondary brain damage and neurobehavioral dysfunction after experimental subarachnoid hemorrhage: possible involvement of TLR4‐mediated inflammatory pathway

Previous studies proved that melatonin protected against secondary brain damage by modulating oxidative stress after experimental subarachnoid hemorrhage (SAH), but it has not been evaluated yet about its effects on inflammatory pathway and secondary cognitive dysfunction in SAH model. This study was undertaken to evaluate the influence of melatonin on toll‐like receptor 4 (TLR4) signaling pathway and neurobehavioral tests after SAH. Adult SD rats were divided into four groups: control group (n = 20), SAH group (n = 20), SAH+vehicle group (n = 20), and SAH+melatonin group (n = 20). The rat SAH model was induced by injection of 0.3 mL fresh arterial, nonheparinized blood into the prechiasmatic cistern in 20 s. In SAH+melatonin group, melatonin was administered i.p. at 150 mg/kg at 2 and 24 hr after the induction of SAH. Cognitive and memory changes were investigated in the Morris water maze. Treatment with melatonin markedly decreased the expressions of TLR4 pathway‐related agents, such as high‐mobility group box 1 (HMGB1), TLR4, nuclear factor‐κB (NF‐κB), myeloid differentiation factor 88 (MyD88), interleukin‐1β (IL‐1β), tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), and inducible nitric oxide synthase (iNOS). Administration of melatonin following SAH significantly ameliorated spatial learning and memory deficits in this prechiasmatic blood injection model. Staining of apoptosis and necrosis indicated that fewer positive cells appeared in melatonin‐treated group than SAH+vehicle group. In conclusion, melatonin may attenuate neurobehavioral dysfunction in this SAH model, and melatonin exhibits neuroprotection possibly not only through anti‐oxidative pathway but also anti‐inflammatory signaling after experimental SAH.     

Melatonin attenuates neuronal apoptosis through up‐regulation of K+–Cl− cotransporter KCC2 expression following traumatic brain injury in rats

Traumatic brain injury (TBI) initiates a complex cascade of neurochemical and signaling changes that leads to neuronal apoptosis, which contributes to poor outcomes for patients with TBI. The neuron‐specific K⁺–Cl^? cotransporter‐2 (KCC2), the principal Cl^? extruder in adult neurons, plays an important role in Cl^? homeostasis and neuronal function. This present study was designed to investigate the expression pattern of KCC2 following TBI and to evaluate whether or not melatonin is able to prevent neuronal apoptosis by modulating KCC2 expression in a Sprague Dawley rat controlled cortical impact model of TBI. The time course study showed decreased mRNA and protein expression of KCC2 in the ipsilateral peri‐core parietal cortex after TBI. Double immunofluorescence staining demonstrated that KCC2 is located in the plasma membrane of neurons. In addition, melatonin (10 mg/kg) was injected intraperitoneally at 5 minutes and repeated at 1, 2, 3, and 4 hours after brain trauma, and brain samples were extracted 24 hours after TBI. Compared to the vehicle group, melatonin treatment altered the down‐regulation of KCC2 expression in both mRNA and protein levels after TBI. Also, melatonin treatment increased the protein levels of brain‐derived neurotrophic factor (BDNF) and phosphorylated extracellular signal‐regulated kinase (p‐ERK). Simultaneously, melatonin administration ameliorated cortical neuronal apoptosis, reduced brain edema, and attenuated neurological deficits after TBI. In conclusion, our findings suggested that melatonin restores KCC2 expression, inhibits neuronal apoptosis and attenuates secondary brain injury after TBI, partially through activation of BDNF/ERK pathway.     

Melatonin modulates neonatal brain inflammation through endoplasmic reticulum stress,autophagy, and miR‐34a/silent information regulator 1 pathway

Maternal infection/inflammation represents one of the most important factors involved in the etiology of brain injury in newborns. We investigated the modulating effect of prenatal melatonin on the neonatal brain inflammation process resulting from maternal intraperitoneal (i.p.) lipopolysaccharide (LPS) injections. LPS (300 μg/kg) was administered to pregnant rats at gestational days 19 and 20. Melatonin (5 mg/kg) was administered i.p. at the same time as LPS. Melatonin counteracted the LPS sensitization to a second ibotenate‐induced excitotoxic insult performed on postnatal day (PND) 4. As melatonin succeeded in reducing microglial activation in neonatal brain at PND1, pathways previously implicated in brain inflammation regulation, such as endoplasmic reticulum (ER) stress, autophagy and silent information regulator 1 (SIRT1), a melatonin target, were assessed at the same time‐point in our experimental groups. Results showed that maternal LPS administrations resulted in an increase in CHOP and Hsp70 protein expression and eIF2α phosphorylation, indicative of activation of the unfolded protein response consequent to ER stress, and a slighter decrease in the autophagy process, determined by reduced lipidated LC3 and increased p62 expression. LPS‐induced inflammation also reduced brain SIRT1 expression and affected the expression of miR‐34a, miR146a, and miR‐126. All these effects were blocked by melatonin. Cleaved‐caspase‐3 apoptosis pathway did not seem to be implicated in the noxious effect of LPS on the PND1 brain. We conclude that melatonin is effective in reducing maternal LPS‐induced neonatal inflammation and related brain injury. Its role as a prophylactic/therapeutic drug deserves to be investigated by clinical studies.     

Melatonin attenuates lipopolysaccharide-induced acute lung inflammation in sleep-deprived mice

Abstract:  Sleep disorders are great problems in modern society. Even minimal changes of sleep can affect health. Especially, patients with pulmonary diseases complain of sleep problems such as sleep disturbance and insomnia. Recent studies have shown an association between sleep deprivation (SD) and inflammation, however, the underlying mechanisms remain unclear. In the present study, we investigated whether melatonin protects against acute lung inflammation in SD. Male ICR mice were deprived sleep using modified multiplatform water bath for 3 days. Acute lung inflammation was induced by lipopolysaccharide (LPS; 5 mg/kg). Melatonin (5 mg/kg) and LPS was administered in SD mice at day 2. Mice were divided into five groups as control, SD, LPS, LPS + SD, and LPS + SD + melatonin (each group, n = 11). Mice were killed on day 3 after treatment of melatonin and LPS for 24 hr. Lung tissues were collected for histological examination and protein analysis. The malondialdehyde (MDA) level was determined for the effect of oxidative stress. Melatonin restored weight loss in LPS + SD. Histological findings revealed alveolar damages with inflammatory cell infiltration in LPS + SD. Melatonin remarkably attenuated the alveolar damages. In western blot analysis, LPS reduced the levels of Bcl-XL and procaspase-3 in SD mice. After treatment with melatonin, the levels of Bcl-XL and procaspase-3 increased when compared with LPS + SD. LPS treatment showed an increase of TUNEL-positive cells, whereas melatonin prevented the increase of cell death in LPS + SD animals. In lipid peroxidation assay, melatonin significantly reduced the elevated MDA level in LPS + SD. Our results suggest that melatonin attenuates acute lung inflammation during SD via anti-apoptotic and anti-oxidative actions.     

4911例颅脑创伤患者的流行病学特征分析

目的 探讨颅脑创伤的发生规律和临床特点.方法 对4 911例颅脑创伤住院患者的性别、年龄、受伤时间、职业、受伤原因、损伤类型、治疗结果等进行分析.结果 本组患者男:女为3.18: 1.00;31～40岁者占25.3%;农民占57.2%;4、5月份发病者占21.52%;车祸致伤占58.8%;创伤发生于普通公路者占59.8%;轻型颅脑损伤占57.5%;病死率为4.6%. 结论 颅脑创伤的发生在年龄、职业、时间、地点、受伤原因、损伤类型等方面均有一定的规律性.     

Melatonin prevents hemorrhagic shock‐induced liver injury in rats through an Akt‐dependent HO‐1 pathway

Abstract: Although melatonin treatment following trauma‐hemorrhage or ischemic reperfusion prevents organs from dysfunction and injury, the precise mechanism remains unknown. This study tested whether melatonin prevents liver injury following trauma‐hemorrhage involved the protein kinase B (Akt)‐dependent heme oxygenase (HO)‐1 pathway. After a 5‐cm midline laparotomy, male rats underwent hemorrhagic shock (mean blood pressure approximately 40 mmHg for 90 min) followed by fluid resuscitation. At the onset of resuscitation, rats were treated with vehicle, melatonin (2 mg/kg), or melatonin plus phosphoinositide 3‐kinase (PI3K) inhibitor wortmannin (1 mg/kg). At 2 hr after trauma‐hemorrhage, the liver tissue myeloperoxidase activity, malondialdehyde, adenosine triphosphate, serum alanine aminotransferase, and aspartate aminotransferase levels were significantly increased compared with sham‐operated control. Trauma‐hemorrhage resulted in a significant decrease in the Akt activation in comparison with the shams (relative density, 0.526 ± 0.031 versus 1.012 ± 0.066). Administration of melatonin following trauma‐hemorrhage normalized liver Akt phosphorylation (0.993 ± 0.061), further increased mammalian target of rapamycin (mTOR) activation (5.263 ± 0.338 versus 2.556 ± 0.225) and HO‐1 expression (5.285 ± 0.325 versus 2.546 ± 0.262), and reduced cleaved caspase‐3 levels (2.155 ± 0.297 versus 5.166 ± 0.309). Coadministration of wortmannin abolished the melatonin‐mediated attenuation of the shock‐induced liver injury markers. Our results collectively suggest that melatonin prevents hemorrhagic shock‐induced liver injury in rats through an Akt‐dependent HO‐1 pathway.     

Melatonin and ischemia-reperfusion injury of the brain

Abstract:  This review summarizes the reports that have documented the neuroprotective effects of melatonin against ischemia/reperfusion brain injury. The studies were carried out on several species, using models of acute focal or global cerebral ischemia under different treatment schedules. The neuroprotective actions of melatonin were observed during critical evolving periods for cell processes of immediate or delayed neuronal death and brain injury, early after the ischemia/reperfusion episode. Late neural phenomena accounting either for brain damage or neuronal repair, plasticity and functional recovery taking place after ischemia/reperfusion have been rarely examined for the protective actions of melatonin. Special attention has been paid to the advantageous characteristics of melatonin as a neuroprotective drug: bioavailability into brain cells and cellular organelles targeted by morpho-functional derangement; effectiveness in exerting several neuroprotective actions, which can be amplified and prolonged by its metabolites, through direct and indirect antioxidant activity; prevention and reversal of mitochondrial malfunction, reducing inflammation, derangement of cytoskeleton organization, and pro-apoptotic cell signaling; lack of interference with thrombolytic and neuroprotective actions of other drugs; and an adequate safety profile. Thus, the immediate results of melatonin actions in reducing infarct volume, necrotic and apoptotic neuronal death, neurologic deficits, and in increasing the number of surviving neurons, may improve brain tissue preservation. The potential use of melatonin as a neuroprotective drug in clinical trials aimed to improve the outcome of patients suffering acute focal or global cerebral ischemia should be seriously considered.     

Dexamethasone for the treatment of traumatic brain injured patients with brain contusions and pericontusional edema: Study protocol for a prospective,randomized and double blind trial

Background:Traumatic brain injury (TBI) constitutes a leading cause of death and disability. Patients with TBI and cerebral contusions developing pericontusional edema are occasionally given dexamethasone on the belief that this edema is similar to that of tumors, in which the beneficial effect of dexamethasone has been demonstrated.Methods:The DEXCON TBI trial is a multicenter, pragmatic, randomized, triple-blind, placebo controlled trial to quantify the effects of dexamethasone on the prognosis of TBI patients with brain contusions and pericontusional edema. Adult patients who fulfill the elegibility criteria will be randomized to dexamethasone/placebo in a short and descending course: 4 mg/6 h (2 days); 4 mg/8 hours (2 days); 2 mg/6 hours (2 days); 2 mg/8 hours (2 days); 1 mg/8 hours (2 days); 1 mg/12 hours (2 days). The primary outcome is the Glasgow Scale Outcome Extended (GOSE) performed 1 month and 6 months after TBI. Secondary outcomes are: number of episodes of neurological deterioration; symptoms associated with TBI; adverse events; volume of pericontusional edema before and after 12 days of treatment; results of the neuropsychological tests one month and 6 months after TBI. The main analysis will be on an “intention-to-treat” basis. Logistic regression will estimate the effect of dexamethasone/placebo on GOSE at one month and at 6 months, dichotomized in unfavorable outcome (GOSE 1–6) and favorable outcome (GOSE 7–8). Efficacy will also be analyzed using the ''sliding dichotomy’. An interim and safety analysis will be performed including patients recruited during the first year to calculate the conditional power. A study with 600 patients would have 80% power (2 sided alpha = 5%) to detect a 12% absolute increase (from 50% to 62%) in good recovery.Discussion:This is a confirmative trial to elucidate the therapeutic efficacy of dexamethasone in a very specific group of TBI patients: patients with brain contusions and pericontusional edema. This trial could become an important milestone for TBI patients as nowadays there is no effective treatment in this type of patients.Trial Registration:eudraCT: 2019–004038–41; Clinical Trials.gov: {"type":"clinical-trial","attrs":{"text":"NCT04303065","term_id":"NCT04303065"}}NCT04303065.     

Melatonin attenuates methamphetamine‐induced overexpression of pro‐inflammatory cytokines in microglial cell lines

Abstract: Methamphetamine (METH), the most commonly abused drug, has long been known to induce neurotoxicity. METH causes oxidative stress and inflammation, as well as the overproduction of both reactive oxygen species (ROS) and reactive nitrogen species (RNS). The role of METH‐induced brain inflammation remains unclear. Imbroglio activation contributes to the neuronal damage that accompanies injury, disease and inflammation. METH may activate microglia to produce neuroinflammatory molecules. In highly aggressively proliferating immortalized (HAPI) cells, a rat microglial cell line, METH reduced cell viability in a concentration‐ and time‐dependent manner and initiated the expression of interleukin 1β (IL‐1β), interleukin 6 (IL‐6) and tumor necrosis factor α. METH also induced the production of both ROS and RNS in microglial cells. Pretreatment with melatonin, a major secretory product of the pineal gland, abolished METH‐induced toxicity, suppressed ROS and RNS formation and also had an inhibitory effect on cytotoxic factor gene expression. The expression of cytotoxic factors produced by microglia may contribute to central nervous system degeneration in amphetamine abusers. Melatonin attenuates METH toxicity and inhibits the expression of cytotoxic factor genes associated with ROS and RNS neutralization in HAPI microglia. Thus, melatonin might be one of the neuroprotective agents induced by METH toxicity and/or other immunogens.     

褪黑素通过介导线粒体自噬改善糖尿病心肌梗死后心肌损伤

目的 探讨褪黑素通过介导线粒体自噬对糖尿病(DM)心肌梗死(MI)后心肌损伤的保护作用及相关机制。方法 将32只C57BL/6J雄性小鼠按照随机数表法随机分为4组,每组8只:(1)假手术组(sham组);(2)糖尿病组(DM组);(3)糖尿病急性心肌梗死组(DMI组);(4)糖尿病急性心肌梗死+褪黑素组(DMI+Mel组)。4周后行超声心动图检测小鼠心脏功能。取心脏行切片染色,检测小鼠心肌间质纤维化程度和心肌细胞凋亡水平。培养H9c2细胞,分为以下4组:(1)对照组(CON组);(2)高糖高脂组(HG/HF组);(3)高糖高脂缺氧组(HG/HF+hypoxia组);(4)HG/HF+hypoxia+Mel组。行相应处理后,采用蛋白质印迹法检测B细胞淋巴瘤-2蛋白(Bcl-2)、含半胱氨酸的天冬氨酸蛋白水解酶-3蛋白(Caspase-3)、Bcl-2关联X蛋白(Bax)和微管相关蛋白1轻链3-β(LC3)、死骨片蛋白1(P62)、帕金蛋白(Parkin)等线粒体自噬相关蛋白的表达,采用荧光素酶法检测细胞内三磷酸腺苷(ATP)浓度。采用SPSS 25.0统计软件进行数据分析。根据数据类型,分别采用方差分析和Dunnett法进行组间比较。结果 与sham组相比,DMI组和DMI+Mel组小鼠的左心室射血分数(LVEF)和左室短轴缩短率(LVFS)显著降低;左室收缩末期内径(LVESD)、左室舒张末期内径(LVEDD)、心肌细胞横截面积、间质纤维化程度和细胞凋亡率显著升高,差异均有统计学意义(P＜0.05)。与DMI组相比,DMI+Mel组小鼠的心功能明显改善;LVESD、LVEDD、心肌细胞横截面积、间质纤维化程度和细胞凋亡率显著降低,差异均有统计学意义(P＜0.05)。与CON组相比,HG/HF组和HG/HF+hypoxia组细胞Bax、Caspase-3、P62表达显著升高,Bcl-2、LC3-Ⅱ/LC3-Ⅰ及Parkin水平显著降低,细胞内ATP含量显著降低,差异均有统计学意义(P＜0.05)。与HG/HF组和HG/HF+hypoxia组相比,HG/HF+hypoxia+Mel组细胞Bax、Caspase-3、P62表达显著降低,Bcl-2、LC3-Ⅱ/LC3-Ⅰ、Parkin水平显著升高,细胞内ATP含量显著升高,差异均有统计学意义(P＜0.05)。结论 褪黑素可通过增强线粒体自噬减轻糖尿病心肌梗死后心肌细胞的损伤,从而改善心脏功能。     

重型颅脑损伤治疗的研究进展

重型颅脑损伤是神经外科临床常见的危重症之一,其病情复杂,治疗难度较大,病死率高,其治疗主要采取综合的方法。多年来,经国内外神经外科专家的不断探索和研究,对重型颅脑损伤的治疗取得了巨大的成果,但仍存在很大难点和不确定的因素,故其治疗方法仍是神经外科领域目前的研究课题。该文主要就近年来国内外重型颅脑损伤治疗的研究进展进行综述。     

Monitoring of glucose in brain, adipose tissue, and peripheral blood in patients with traumatic brain injury: a microdialysis study

Background:

Episodes of hyperglycemia are considered to be a secondary insult in traumatically brain-injured patients and have been shown to be associated with impaired outcome. Intensive insulin therapy to maintain a strict glucose level has been suggested to decrease morbidity and mortality in critically ill patients but this aggressive insulin treatment has been challenged. One aspect of strict glucose control is the risk of developing hypoglycemia. Extracellular intracerebral hypoglycemia monitored by intracerebral microdialysis has been shown to correlate with poor outcome. Monitoring of blood glucose during neurointensive care is important because adequate glucose supply from the systemic circulation is crucial to maintain the brain''s glucose demand after brain injury. This study investigates the correlation of glucose levels in peripheral blood, subcutaneous (SC) fat, and extracellular intracerebral tissue in patients with severe traumatic brain injury during neurointensive care.

Methods:

In this study, we included 12 patients with severe traumatic brain injury. All patients received one microdialysis catheter each, with a membrane length of 10 mm (CMA 70, CMA Microdialysis AB) in the injured hemisphere of the brain and in the noninjured hemisphere of the brain. An additional microdialysis catheter with a membrane length of 30 mm (CMA 60, CMA Microdialysis AB) was placed in the periumbilical subcutaneous adipose tissue. We studied the correlation among levels of glucose measured in peripheral blood, adipose tissue, and the noninjured hemisphere of the brain during the first 12 hours and during 3 consecutive days in neurointensive care.

Results:

We found a significant positive correlation between levels of glucose in peripheral blood, SC fat, and the noninjured brain during the initial 12 hours but not in injured brain. However, the result varied between the patients during the 3-day measurements. In 7 patients, there was a significant positive correlation between glucose in blood and noninjured brain, while in 4 patients this correlation was poor. In 4 patients, there was a significant positive correlation in injured brain and blood. Furthermore, there was a significant correlation between brain and adipose tissue glucose during the 3-day measurements in 11 out of 12 patients.

Conclusion:

This study indicates that there is a good correlation between blood glucose and adipose tissue during initial and later time points in the neurointensive care unit whereas the correlation between blood and brain seems to be more individualized among patients. This emphasizes the importance of using intracerebral microdialysis to ensure adequate intracerebral levels of glucose in patients suffering from severe traumatic brain injury and to detect hypoglycemia in the brain despite normal levels of blood glucose.     

颅脑创伤患者血清抗脑抗体水平的变化及意义

目的观察创伤性颅脑损伤患者血清抗脑抗体（ABAB）水平的变化,并探讨其临床意义。方法采用ELISA法检测49例颅脑创伤患者（伤后3d、1周、2周、3周、1个月、2个月、6个月、9个月）及47例健康体检者血清中的ABAB。结果颅脑创伤患者各时间点血清ABAB水平均高于健康体检者（P均〈0．05）;伤后1周重型颅脑损伤者血清ABAB水平高于中、轻型颅脑伤者（P〈0．01）。结论创伤性颅脑损伤后血清ABAB水平明显升高,可作为判断神经系统损伤程度和预后的指标。     

Melatonin‐induced increase in sensitivity of human hepatocellular carcinoma cells to sorafenib is associated with reactive oxygen species production and mitophagy

Effects of sorafenib in hepatocellular carcinoma (HCC) are frequently transient due to tumor‐acquired resistance, a phenotype that could be targeted by other molecules to reduce this adaptive response. Because melatonin is known to exert antitumor effects in HCC cells, this study investigated whether and how melatonin reduces resistance to sorafenib. Susceptibility to sorafenib (10 nmol/L to 50 μmol/L) in the presence of melatonin (1 and 2 mmol/L) was assessed in HCC cell lines HepG2, HuH7, and Hep3B. Cell viability was reduced by sorafenib from 1 μmol/L in HepG2 or HuH7 cells, and 2.5 μmol/L in Hep3B cells. Co‐administration of melatonin and sorafenib exhibited a synergistic cytotoxic effect on HepG2 and HuH7 cells, while Hep3B cells displayed susceptibility to doses of sorafenib that had no effect when administrated alone. Co‐administration of 2.5 μmol/L sorafenib and 1 mmol/L melatonin induced apoptosis in Hep3B cells, increasing PARP hydrolysis and BAX expression. We also observed an early colocalization of mitochondria with lysosomes, correlating with the expression of mitophagy markers PINK1 and Parkin and a reduction of mitofusin‐2 and mtDNA compared with sorafenib administration alone. Moreover, increased reactive oxygen species production and mitochondrial membrane depolarization were elicited by drug combination, suggesting their contribution to mitophagy induction. Interestingly, Parkin silencing by siRNA to impair mitophagy significantly reduced cell killing, PARP cleavage, and BAX expression. These results demonstrate that the pro‐oxidant capacity of melatonin and its impact on mitochondria stability and turnover via mitophagy increase sensitivity to the cytotoxic effect of sorafenib.