Lipopolysaccharide exacerbates depressive-like behaviors in obese rats through complement C1q-mediated synaptic elimination by microglia

AIM

Prolonged high-fat diet (HFD) consumption has been shown to impair cognition and depression. The combined effects of HFD and lipopolysaccharide (LPS) administration on those outcomes have never been thoroughly investigated. This study investigated the effects of LPS, HFD consumption, and a combination of both conditions on microglial dysfunction, microglial morphological alterations, synaptic loss, cognitive dysfunction, and depressive-like behaviors.

METHODS

Sixty-four male Wistar rats were fed either a normal diet (ND) or HFD for 12 weeks, followed by single dose-subcutaneous injection of either vehicle or LPS. Then, cognitive function and depressive-like behaviors were assessed. Then, rats were euthanized, and the whole brain, hippocampus, and spleen were collected for further investigation, including western blot analysis, qRT-PCR, immunofluorescence staining, and brain metabolome determination.

RESULTS

HFD-fed rats developed obese characteristics. Both HFD-fed rats with vehicle and ND-fed rats with LPS increased cholesterol and serum LPS levels, which were exacerbated in HFD-fed rats with LPS. HFD consumption, but not LPS injection, caused oxidative stress, blood-brain barrier disruption, and decreased neurogenesis. Both HFD and LPS administration triggered an increase in inflammatory genes on microglia and astrocytes, increased c1q colocalization with microglia, and increased dendritic spine loss, which were exacerbated in the combined conditions. Both HFD and LPS altered neurotransmitters and disrupted brain metabolism. Interestingly, HFD consumption, but not LPS, induced cognitive decline, whereas both conditions individually induced depressive-like behaviors, which were exacerbated in the combined conditions.

CONCLUSIONS

Our findings suggest that LPS aggravates metabolic disturbances, neuroinflammation, microglial synaptic engulfment, and depressive-like behaviors in obese rats.

Mitochondrial Fusion Promoter Given During Ischemia Has Greater Neuroprotective Efficacy Than When Given at Onset of Reperfusion in Rats with Cardiac Ischemia/Reperfusion Injury

BACKGROUND

Cardiac ischemia/reperfusion (I/R) injury has been shown to impose deleterious effects not only on the heart but also on the brain. Our previous study demonstrated that pretreatment with a mitochondrial fusion promoter (M1) provided central neuroprotective effects following cardiac I/R injury.

OBJECTIVE

To investigate the effects of M1 given during the ischemic phase and M1 given at the beginning of reperfusion on brain pathologies following cardiac I/R.

METHODS

Male Wistar rats were randomly divided into either a sham operation (n = 6) or cardiac I/R injury (n = 18) group. Rats with cardiac I/R injury were then randomly divided into 3 subgroups: 1) Control, 2) M1 treatment during cardiac ischemia (2 mg/kg, intravenous (i.v.)), and 3) M1 treatment at the beginning of reperfusion (2 mg/kg, i.v.). After euthanasia, the brain of each rat was removed for further analysis.

RESULTS

Cardiac I/R injury caused brain mitochondrial dynamic imbalance, brain mitochondrial dysfunction, brain apoptosis, microglial dysmorphology, brain inflammation, tau hyperphosphorylation, and synaptic dysplasticity. M1 treatment at both time points effectively improved these parameters. M1 given during the ischemic phase had greater efficacy with regard to preventing brain mitochondrial dysfunction and suppressing brain inflammation, when compared to M1 given at the beginning of reperfusion.

CONCLUSIONS

Our findings suggest that treatment with this mitochondrial fusion promoter prevents mitochondrial dynamic imbalance in the brain of rats with cardiac I/R injury, thereby attenuating brain pathologies. Interestingly, giving the mitochondrial fusion promoter during the ischemic phase exerted greater neuroprotection than if given at the beginning of reperfusion.

Cyclosorus Terminans Extract Alleviates Neuroinflammation in Insulin Resistant Rats

High-fat diet consumption for an extended period causes obesity, systemic metabolic disturbance, and brain insulin resistance, resulting in neuroinflammation. Although the beneficial effect of Cyclosorus terminans extract on obesity-related insulin resistance has been demonstrated, little is known about how it affects neuroinflammation and brain insulin resistance in obese rats. Male Wistar rats were given either a normal diet (ND, n = 6) or a high-fat diet (HFD, n = 24) for a total of 14 weeks. At the beginning of the week, 13 rats in the ND group were given vehicle orally for 2 weeks, while rats on HFD diets were randomized to one of four groups and given either vehicle, 100 mg/kg/day of Cyclosorus terminans extract, 200 mg/kg/day of Cyclosorus terminans extract, or 20 mg/kg/day of pioglitazone orally for 2 weeks. After the experimental period, blood and brain samples were taken to assess metabolic and brain parameters. HFD-fed rats had obesity, systemic and brain insulin resistance, brain inflammation, microglial and astrocyte hyperactivity, and brain necroptosis. Treatment with 200 mg/kg/day of Cyclosorus terminans extract and pioglitazone equally attenuated obesity, insulin resistance, brain insulin dysfunction, and neuroinflammation in insulin resistant rats. Our findings suggest that Cyclosorus terminans extract may hold promise as a therapeutic agent for insulin resistance and neuroinflammation in obese conditions.

Long-term lifestyle intervention is superior to transient modification for neuroprotection in D-galactose-induced aging rats

AIMS

To investigate whether transient dietary restriction or aerobic exercise in young adulthood exert long-lasting protection against brain aging later in life.

MAIN METHODS

Seven-week-old male Wistar rats were divided into 2 groups and given either normal saline as a vehicle (n = 8) or 150 mg/kg/day of D-galactose (n = 40) for 28 weeks, the D-galactose being used to induce aging. At week 13 of the experiment, D-galactose-treated rats were further divided into 5 groups, 1) no intervention, 2) transient dietary restriction for 6 weeks (week 13-18), 3) transient exercise for 6 weeks (week 13-18), 4) long-term dietary restriction for 16 weeks (week 13-28), and 5) long-term exercise for 16 weeks (week 13-28). At the end of week 28, cognitive function was examined, followed by molecular studies in the hippocampus.

KEY FINDINGS

Our results showed that either long-term dietary restriction or aerobic exercise effectively attenuated cognitive function in D-galactose-treated rats via the attenuation of oxidative stress, cellular senescence, Alzheimer's-like pathology, neuroinflammation, and improvements in mitochondria, brain metabolism, adult neurogenesis, and synaptic integrity. Although transient interventions provided benefits in some brain parameters in D-galactose-treated rats, an improvement in cognitive function was not observed.

SIGNIFICANCE

Our findings suggested that transient lifestyle interventions failed to exert a long-lasting protective effect against brain aging. Hence, novel drugs mimicking the neuroprotective effect of long-term dietary restriction or exercise and the combination of the two since young age appear to be more appropriate treatments for the elderly who are unable to engage in long-term dietary restriction or exercise.

Ferroptosis inhibitor improves cardiac function more effectively than inhibitors of apoptosis and necroptosis through cardiac mitochondrial protection in rats with iron-overloaded cardiomyopathy

Iron overload cardiomyopathy (IOC) is the leading cause of death in cases of iron overload in patients. Previous studies demonstrated that iron overload led to cardiomyocyte dysfunction and death through multiple pathways including apoptosis, necroptosis and ferroptosis. However, the dominant cell death pathway in the iron-overloaded heart needs clarification. We tested the hypothesis that ferroptosis, an iron-dependent cell death, plays a dominant role in IOC, and ferroptosis inhibitor exerts greater efficacy than inhibitors of apoptosis and necroptosis on improving cardiac function in iron-overloaded rats. Iron dextran was injected intraperitoneally into male Wistar rats for four weeks to induce iron overload. Then, the rats were divided into 5 groups: treated with vehicle, apoptosis inhibitor (z-VAD-FMK), necroptosis inhibitor (Necrostatin-1), ferroptosis inhibitor (Ferrostatin-1) or iron chelator (deferoxamine) for 2 weeks. Cardiac function, mitochondrial function, apoptosis, necroptosis and ferroptosis were determined. The increased expression of apoptosis-, necroptosis- and ferroptosis-related proteins, were associated with impaired cardiac and mitochondrial function in iron-overloaded rats. All cell death inhibitors attenuated cardiac apoptosis, necroptosis and ferroptosis in iron-overloaded rats. Ferrostatin-1 was more effective than the other drugs in diminishing mitochondrial dysfunction and Bax/Bcl-2 ratio. Moreover, both Ferrostatin-1 and deferoxamine reversed iron overload-induced cardiac dysfunction as indicated by restored left ventricular ejection fraction and E/A ratio, whereas z-VAD-FMK and Necrostatin-1 only partially improved this parameter. These results indicated that ferroptosis could be the predominant form of cardiomyocyte death in IOC, and that inhibiting ferroptosis might be a potential novel treatment for IOC.

Vagus nerve stimulation and acetylcholinesterase inhibitor donepezil provide cardioprotection against trastuzumab-induced cardiotoxicity in rats by attenuating mitochondrial dysfunction

Trastuzumab (Trz) is a targeted anticancer drug for human epidermal growth factor receptor 2 (HER2)-positive tumors, as Trz-induced cardiotoxicity (TIC) is commonly observed in Trz-treated patients. Since cardiac autonomic modulation with electrical vagus nerve stimulation (VNS) and acetylcholinesterase (AChE) inhibitors exerts cardioprotection against various heart diseases, the comparative effects of electrical VNS and an AChE inhibitor (donepezil) on cardiac and mitochondrial functions and programmed cell death pathways in TIC are not known. VNS devices were implanted in thirty-two male Wistar rats and were divided into 4 groups: (i) Control-Sham (CSham), (ii) Trz-Sham (TSham), (iii) Trz-VNS (TVNS), and (iv) Trz-donepezil (TDPZ). Rats in the Trz-treated groups were intraperitoneally injected with Trz (4 mg/kg/day) for 7 days, while CSham rats were injected with NSS. VNS devices were activated in the TVNS rats during the 7-day Trz treatment, but not in the sham rats. Rats in the TDPZ group received donepezil orally (5 mg/kg/day) for 7 days. At the end, left ventricular (LV) function and heart rate variability were evaluated, and heart tissue was collected for biochemical and histological analysis. Trz rats showed LV dysfunction and cardiac sympathovagal imbalance. In addition, mitochondrial function and dynamics were impaired in TIC rats. Trz also increased cardiomyocyte death by inducing apoptosis, pyroptosis, and ferroptosis. Electrical VNS and donepezil had similar efficacy in alleviating cardiac mitochondrial dysfunction, dynamic imbalances, and cardiomyocyte death, leading to improved LV function. These findings suggested that parasympathetic activation via either VNS or an AChE inhibitor could be a promising therapeutic intervention against TIC.

Acetylcholine receptor agonists effectively attenuated multiple program cell death pathways and improved left ventricular function in trastuzumab-induced cardiotoxicity in rats

AIMS

Cardiotoxicity is a seriously debilitating complication of trastuzumab (TRZ) therapy in patients with cancer as a consequence of overexpression of the human epidermal growth factor receptor 2. Although most TRZ-induced cardiotoxicity (TIC) cases are reversible, some patients experience chronic cardiac dysfunction, and these irreversible concepts may be associated with cardiomyocyte death. Acetylcholine receptor (AChR) activation has been shown to exert cardioprotection in several heart diseases, but the effects of AChR agonists against TIC have not been investigated.

MAIN METHOD

Forty adult male Wistar rats were randomized into 5 groups: (i) CON (0.9 % normal saline), (ii) TRZ (4 mg/kg/day), (iii) TRZ + α7nAChR agonist (PNU-282987: 3 mg/kg/day), (iv) TRZ + mAChR agonists (bethanechol: 12 mg/kg/day), and (v) TRZ + combined treatment (Combined PNU-282987 and bethanechol).

KEY FINDINGS

The progression of TIC was driven by mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including by pyroptosis, ferroptosis, and apoptosis, which were significantly alleviated by α7nAChR and mAChR agonists. Interestingly, necroptosis was not associated with development of TIC. More importantly, the in vitro study validated the cytoprotective effects of AChR activation in TRZ-treated H9c2 cells, while not interfering with the anticancer properties of TRZ. All of these findings indicated that TRZ induced mitochondrial dysfunction, autophagic deficiency, and excessive myocyte death including pyroptosis, ferroptosis, and apoptosis, leading to impaired cardiac function. These pathological alterations were attenuated by α7nAChR and mAChR agonists.

SIGNIFICANCE

α7nAChR and mAChR agonists might be used as a future therapeutic target in the mitigation of TIC.

Acetylcholinesterase inhibition protects against trastuzumab-induced cardiotoxicity through reducing multiple programmed cell death pathways

BACKGROUND

Trastuzumab (Trz)-induced cardiotoxicity (TIC) is one of the most common adverse effects of targeted anticancer agents. Although oxidative stress, inflammation, mitochondrial dysfunction, apoptosis, and ferroptosis have been identified as potential mechanisms underlying TIC, the roles of pyroptosis and necroptosis under TIC have never been investigated. It has been shown that inhibition of acetylcholinesterase function by using donepezil exerts protective effects in various heart diseases. However, it remains unknown whether donepezil exerts anti-cardiotoxic effects in rats with TIC. We hypothesized that donepezil reduces mitochondrial dysfunction, inflammation, oxidative stress, and cardiomyocyte death, leading to improved left ventricular (LV) function in rats with TIC.

METHODS

Male Wistar rats were randomly assigned to be Control or Trz groups (Trz 4 mg/kg/day, 7 days, I.P.). Rats in Trz groups were assigned to be co-treated with either drinking water (Trz group) or donepezil 5 mg/kg/day (Trz + DPZ group) via oral gavage for 7 days. Cardiac function, heart rate variability (HRV), and biochemical parameters were evaluated.

RESULTS

Trz-treated rats had impaired LV function, HRV, mitochondrial function, and increased inflammation and oxidative stress, leading to apoptosis, ferroptosis, and pyroptosis. Donepezil co-treatment effectively decreased those adverse effects of TIC, resulting in improved LV function. An in vitro study revealed that the cytoprotective effects of donepezil were abolished by a muscarinic acetylcholine receptor (mAChR) antagonist.

CONCLUSIONS

Donepezil exerted cardioprotection against TIC via attenuating mitochondrial dysfunction, oxidative stress, inflammation, and cardiomyocyte death, leading to improved LV function through mAChR activation. This suggests that donepezil could be a novel intervention strategy in TIC.

Treatment with apoptosis inhibitor restores cognitive impairment in rats with myocardial infarction

We previously reported that apoptosis is responsible for cognitive impairment in rats with myocardial infarction (MI). Acute administration of an apoptosis inhibitor (Z-vad) effectively reduced brain inflammation in rats with cardiac ischemia/reperfusion injury. However, the beneficial effects of Z-vad on cognitive function, brain inflammation, mitochondrial function, cell death pathways, and neurogenesis in MI rats have not been investigated. Male rats were divided into sham or MI groups (left anterior descending coronary ligation). A successful MI was determined by a reduction of ejection fraction <50 %. Then, MI rats were allocated to receive vehicle, enalapril (10 mg/kg, a positive control), and Z-vad (1 mg/kg) for 4 weeks. Cardiac function, cognitive function, and molecular analysis were investigated. MI rats exhibited cardiac dysfunction, cognitive impairment, blood brain barrier (BBB) breakdown, dendritic spine loss, which were accompanied by an upregulation of oxidative stress, mitochondrial dysfunction, and apoptosis. Chronic treatment with Z-vad attenuated cardiac dysfunction following MI to the same extent as enalapril. Z-vad successfully improved cognitive function and restored dendritic spine density in MI rats through a reduction of systemic oxidative stress and brain mitochondrial dysfunction similar to enalapril. Moreover, Z-vad provided greater efficacy than enalapril in enhancing mitophagy, neurogenesis, synaptic proteins and reducing apoptosis in hippocampus of MI rats. Nevertheless, neither Z-vad nor enalapril increased BBB tight junction protein. In conclusion, treatment with an apoptosis inhibitor reduced cognitive impairment in MI rats via reducing oxidative stress, mitochondrial dysfunction, apoptosis, and restoring dendritic spine density, together with enhancing mitophagy and neurogenesis.

Chronic D-Galactose Administration Induces Natural Aging Characteristics, in Rat's Brain and Heart

We aimed to investigate the effect of chronic D-galactose exposure on the mimicking of natural aging processes based upon the hallmarks of aging. Seven-week-old male Wistar rats (n = 12) were randomly assigned to receive either normal saline solution as a vehicle (n = 6) or 150mg/kg/day of D-galactose subcutaneously for 28 weeks. Seventeen-month-old rats (n = 6) were also included as the chronologically aged controls. At the end of week 28 of the experiment (when the rats reach 35 weeks old and 24 months old), all rats were sacrificed for brain and heart collection. Our results showed that chronic D-galactose exposure mimicked natural aging characteristics of the brain and the heart in terms of deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, and functional impairment. All of which highlight the potential of D-galactose as a substance for inducing brain and cardiac aging in animal experiments. DATA AVAILABILITY: The data that support the findings of this study are available from the corresponding author upon reasonable request.

Higher untrained fitness exerts a neuroprotection in Independence to caloric restriction or exercise in high-fat diet-induced obesity

We investigated whether weight maintenance following short-term caloric restriction or exercise exerted neuroprotective effects on obesity induced by a high-fat diet. We also sought to identify whether the neuroprotective effects of higher untrained fitness persisted in the obese condition, both with and without caloric restriction or exercise. Male Wistar rats were fed with either a normal diet (ND) or a high-fat diet (HFD) for 12 weeks. At week 12, untrained fitness and blood metabolic parameters were measured. The ND-fed rats continuously received a ND for 16 additional weeks. HFD-fed rats were randomly assigned to 5 groups as of the followings: 1) an additional 16 weeks of HFD without intervention, 2) 10-week weight maintenance following 6-week short-term caloric restriction, 3) long-term caloric restriction (16 weeks), 4) 10-week weight maintenance following 6 weeks of HFD plus short-term exercise, and 5) HFD plus long-term exercise (16 weeks). Untrained fitness, blood metabolic parameters, and behavioral tests were then determined. Thereafter, the rats were euthanized for molecular studies. Our results demonstrated that long-term caloric restriction had the greatest systemic metabolic benefit among all interventions. Long-term caloric restriction and exercise equally attenuated HFD-induced cognitive impairment by improving synaptic function, blood-brain barrier integrity, mitochondrial health, and neurogenesis, and reducing oxidative stress, neuroinflammation, apoptosis, and Alzheimer's-related pathology. Weight maintenance following short-term caloric restriction showed no benefit to neurogenesis. Weight maintenance following short-term exercise exerted no benefit on synaptic function, neuronal insulin signaling and metabolism, autophagy, and neurogenesis. Interestingly, we found that higher untrained fitness level at week 12 showed positive correlations with more favorable brain profiles at week 28 in HFD-fed rats, both with and without caloric restriction or exercise. All of these findings suggested that higher untrained fitness exerts neuroprotection in HFD-induced obesity independently of caloric restriction or exercise. Therefore, targeting enhancement of untrained fitness may lead to more effective treatment of neurodegeneration in obese condition.

Acute administration of myeloid differentiation factor 2 inhibitor and N-acetyl cysteine attenuate brain damage in rats with cardiac ischemia/reperfusion injury

Inflammation and oxidative stress are mechanisms which potentially underlie the brain damage that can occur after cardiac ischemic and reperfusion (I/R) injury. 2i-10 is a new anti-inflammatory agent, acting via direct inhibition of myeloid differentiation factor 2 (MD2). However, the effects of 2i-10 and the antioxidant N-acetylcysteine (NAC) on pathologic brain in cardiac I/R injury are unknown. We hypothesized that 2i-10 and NAC offer similar neuroprotection levels against dendritic spine reduction through attenuation of brain inflammation, loss of tight junction integrity, mitochondrial dysfunction, reactive gliosis, and suppression of AD protein expression in rats with cardiac I/R injury. Male rats were allocated to either sham or acute cardiac I/R group (30 min of cardiac ischemia and 120 min of reperfusion). Rats in cardiac I/R group were given one of following treatments intravenously at the onset of reperfusion: vehicle, 2i-10 (20 or 40 mg/kg), and NAC (75 or 150 mg/kg). The brain was then used to determine biochemical parameters. Cardiac I/R led to cardiac dysfunction with dendritic spine loss, loss of tight junction integrity, brain inflammation, and mitochondrial dysfunction. Treatment with 2i-10 (both doses) effectively reduced cardiac dysfunction, tau hyperphosphorylation, brain inflammation, mitochondrial dysfunction, dendritic spine loss, and improved tight junction integrity. Although both doses of NAC effectively reduced brain mitochondrial dysfunction, treatment using a high dose of NAC reduced cardiac dysfunction, brain inflammation, and dendritic spine loss. In conclusion, treatment with 2i-10 and a high dose of NAC at the onset of reperfusion alleviated brain inflammation and mitochondrial dysfunction, consequently reducing dendritic spine loss in rats with cardiac I/R injury.

Melatonin and metformin ameliorated trastuzumab-induced cardiotoxicity through the modulation of mitochondrial function and dynamics without reducing its anticancer efficacy

Trastuzumab has an impressive level of efficacy as regards antineoplasticity, however it can cause serious cardiotoxic side effects manifested by impaired cardiac contractile function. Although several pharmacological interventions, including melatonin and metformin, have been reported to protect against various cardiovascular diseases, their potential roles in trastuzumab-induced cardiotoxicity remain elusive. We hypothesized that either melatonin or metformin co-treatment effectively attenuates trastuzumab-mediated cardiotoxicity through attenuating the impaired mitochondrial function and mitochondrial dynamics. Male Wistar rats were divided into control (normal saline, n = 8) and trastuzumab group (4 mg/kg/day for 7 days, n = 24). Rats in the trastuzumab group were subdivided into 3 interventional groups (n = 8/group), and normal saline, or melatonin (10 mg/kg/day), or metformin (250 mg/kg/day) were orally administered for 7 consecutive days. Cardiac parameters were determined, and biochemical investigations were carried out on blood and heart tissues. Trastuzumab induced left ventricular (LV) dysfunction by increasing oxidative stress, inflammation, and apoptosis. It also impaired cardiac mitochondrial function, dynamics, and autophagy. Treatment with either melatonin or metformin equally attenuated trastuzumab-induced cardiac injury, indicated by a marked reduction in inflammation, oxidative damage, cardiac mitochondrial injury, mitochondrial dynamic imbalance, autophagy dysregulation, and apoptosis, leading to improved LV function, as demonstrated by increased LV ejection fraction. Melatonin and metformin conferred equal levels of cardioprotection against trastuzumab-induced cardiotoxicity, which may provide novel and promising approaches for management of cardiotoxicity induced by trastuzumab.

Ferrostatin-1 and Z-VAD-FMK potentially attenuated Iron-mediated neurotoxicity and rescued cognitive function in Iron-overloaded rats

AIMS

The present study was aimed to investigate the effects of cell death inhibitors including ferroptosis inhibitor, ferrostatin-1 (FER-1) and a pan-caspase inhibitor, z-VAD-FMK on brain parameters and cognitive function in iron-overloaded rats.

MAIN METHODS

Male Wistar rats (n = 30) were divided into 2 groups to receive an intraperitoneal injection with either 10 % dextrose in normal saline solution (NSS) (control group, n = 6) or 100 mg/kg iron dextran (Fe group, n = 24) for 6 weeks. After 4 weeks of injection, Fe-injected rats were subdivided into 4 subgroups (n = 6/subgroup) to subcutaneously receive with 1) vehicle (10 % DMSO in NSS), 2) deferoxamine (25 mg/kg), 3) FER-1 (2 mg/kg), or 4) z-VAD-FMK (1 mg/kg). Control group was received vehicle. All subgroups were received each treatment for 2 weeks. Behavioral tests including the Morris water maze test and novel object recognition test, were performed at the end of treatment. Then, circulating iron levels and brain parameters including blood-brain barrier proteins, iron level, synaptic proteins, and ferroptosis/apoptosis were determined.

KEY FINDINGS

All treatment attenuated iron-overloaded condition, brain pathologies, and the cognitive impairment. FER-1 and z-VAD-FMK provided superior effects than deferoxamine by attenuating loss of synaptic proteins and restoring cognitive function in both hippocampal-dependent and hippocampal-independent manners.

SIGNIFICANCE

These findings suggest that cell death inhibitors act as the novel therapeutic targets for neuroprotection in iron-overloaded condition.

GSDMD-mediated pyroptosis dominantly promotes left ventricular remodeling and dysfunction in post-myocardial infarction: a comparison across modes of programmed cell death and mitochondrial involvement

BACKGROUND

Myocardial infarction (MI) has recently accounted for more than one-third of global mortality. Multiple molecular pathological pathways, such as oxidative stress, inflammation, and mitochondrial dysfunction, have been recognized as possible mechanisms in the development of MI. Furthermore, different phases of ischemic injury following the progression of MI were also associated with multiple types of programmed cell death (PCDs), including apoptosis, necroptosis, ferroptosis, and pyroptosis. However, it remains unknown whether which types of PCDs play the most dominant role in post-myocardial infarction (post-MI).

METHOD

In this study, we used a preclinical rat model of MI induced by permanent left anterior descending coronary artery (LAD) ligation (n = 6) or a sham operated rat model (n = 6). After a 5-week experiment, cardiac function and morphology, mitochondrial studies, and molecular signaling analysis of PCDs were determined.

RESULTS

Herein, we demonstrated that post-MI rats had considerably impaired cardiac geometry, increased oxidative stress, myocardial injuries, and subsequently contractile dysfunction. They also exhibited worsened cardiac mitochondrial function and dynamic imbalance. More importantly, we found that post-MI mediated abundant myocardial cell death through multiple PCDs, including apoptosis, necroptosis, and pyroptosis, but not ferroptosis.

CONCLUSION

In this study, we provide the first insights into the mechanism of PCDs by pyroptosis, which is leveraged as the most dominant mode of cell death after MI.

Melatonin and metformin counteract cognitive dysfunction equally in male rats with doxorubicin-induced chemobrain

Melatonin (Mel) and metformin (Met) show beneficial effects in various brain pathologies. However, the effects of Mel and Met on doxorubicin (DOX)-induced chemobrain remain in need of elucidation. We aimed to investigate whether Mel and Met provide neuroprotective effects on glial dysmorphologies, brain inflammation, oxidative stress, brain mitochondrial dysfunction, apoptosis, necroptosis, neurogenesis, hippocampal dysplasticity, and cognitive dysfunction in rats with DOX-induced chemobrain. Thirty-two male Wistar rats were divided into 2 groups and received normal saline (NSS, as control, n = 8) or DOX (3 mg/kg/day; n = 24) by intraperitoneal (i.p.) injection on days 0, 4, 8, 15, 22, and 29. The DOX-treated group was divided into 3 subgroups receiving either vehicle (NSS; n = 8), Mel (10 mg/kg/day; n = 8), or Met (250 mg/kg/day; n = 8) by gavage for 30 consecutive days. Following this, cognitive function was assessed in all rats. The number of glial cells and their fluorescence intensity had decreased, while the glial morphology in DOX-treated rats showed a lower process complexity. Brain mitochondrial dysfunction, an increase in brain inflammation, oxidative stress, apoptosis and necroptosis, a decrease in the number of hippocampal dendritic spines and neurogenesis, and cognitive decline were also observed in DOX-treated rats. Mel and Met equally improved those brain pathologies, resulting in cognitive improvement in DOX-treated rats. In conclusion, concomitant treatment with either Mel or Met counteract DOX-induced chemobrain by preservation of glial morphology, brain inflammation, brain oxidative stress, brain mitochondrial function, hippocampal plasticity, and brain apoptosis. This study highlighted the role of the glia as key mediators in DOX-induced chemobrain.

Vagus nerve stimulation exerts cardioprotection against doxorubicin-induced cardiotoxicity through inhibition of programmed cell death pathways

The aberration of programmed cell death including cell death associated with autophagy/mitophagy, apoptosis, necroptosis, pyroptosis, and ferroptosis can be observed in the development and progression of doxorubicin-induced cardiotoxicity (DIC). Vagus nerve stimulation (VNS) has been shown to exert cardioprotection against cardiomyocyte death through the release of the neurotransmitter acetylcholine (ACh) under a variety of pathological conditions. However, the roles of VNS and its underlying mechanisms against DIC have never been investigated. Forty adults male Wistar rats were divided into 5 experimental groups: (i) control without VNS (CSham) group, (ii) doxorubicin (3 mg/kg/day, i.p.) without VNS (DSham) group, (iii) doxorubicin + VNS (DVNS) group, (iv) doxorubicin + VNS + mAChR antagonist (atropine; 1 mg/kg/day, ip, DVNS + Atro) group, and (v) doxorubicin + VNS + nAChR antagonist (mecamylamine; 7.5 mg/kg/day, ip, DVNS + Mec) group. Our results showed that doxorubicin insult led to left ventricular (LV) dysfunction through impaired cardiac autonomic balance, decreased mitochondrial function, imbalanced mitochondrial dynamics, and exacerbated cardiomyocyte death including autophagy/mitophagy, apoptosis, necroptosis, pyroptosis, and ferroptosis. However, VNS treatment improved cardiac mitochondrial and autonomic functions, and suppressed excessive autophagy, apoptosis, necroptosis, pyroptosis, and ferroptosis, leading to improved LV function. Consistent with this, ACh effectively improved cell viability and suppressed cell cytotoxicity in doxorubicin-treated H9c2 cells. In contrast, either inhibitors of muscarinic (mAChR) or nicotinic acetylcholine receptor (nAChR) completely abrogated the favorable effects mediated by VNS and acetylcholine. These findings suggest that VNS exerts cardioprotective effects against doxorubicin-induced cardiomyocyte death via activation of both mAChR and nAChR.

Combined caloric restriction and exercise provides greater metabolic and neurocognitive benefits than either as a monotherapy in obesity with or without estrogen deprivation

Neurodegeneration, as indicated by brain dysfunction and cognitive decline, is one of the complications associated with obesity and estrogen deprivation. Calorie restriction and exercise regimes improved brain function in neurodegenerative diseases. However, the comparative effects of a combination of calorie restriction with exercise, calorie restriction, and an exercise regime alone on brain/cognitive function in obesity with or without estrogen deprivation have not been investigated. Sixty female rats were fed a normal diet (ND) or a high-fat diet (HFD) for 27 weeks. At week 13, the ND-fed rats underwent a sham operation with sedentary lifestyle, HFD-fed rats were divided into two groups: each having either a sham operation (HFS) or ovariectomy (HFO). At week 20, HFD-fed rats in each group were divided into four subgroups undergoing either a sedentary lifestyle, calorie restriction, exercise regime or a combination of calorie restriction and exercise for 7 weeks. Insulin resistance, cognitive decline and hippocampal pathologies were found in both HFS and HFO rats. HFO rats had higher levels of insulin resistance and hippocampal reactive oxygen species levels than HFS rats. Calorie restriction decreased metabolic disturbance and hippocampal oxidative stress but failed to attenuate cognitive decline in HFS and HFO rats. Exercise attenuated metabolic/hippocampal dysfunctions, resulting in improved cognition only in HFS rats. Combined therapies restored brain function, and cognitive function in HFS and HFO rats. Therefore, a combination of calorie restriction with exercise is probably the greatest lifestyle modification to diminish the brain pathologies and cognitive decline in obesity with or without estrogen deprivation.

Myeloid differentiation factor 2 inhibitor and N-acetyl cysteine synergistically reduced left ventricular dysfunction in rats with cardiac ischemia/reperfusion injury

Background

Myeloid differentiation factor 2 inhibitor (MD2i) is a novel anti-inflammatory agent that exerts favorable outcomes in various diseases including cardiac ischemia/reperfusion (I/R) injury. However, whether a potent antioxidant N-acetyl cysteine (NAC) can augment the beneficial effects of MD2i in rats with cardiac I/R injury have never been investigated.

Purpose

We tested the hypothesis that NAC increases the beneficial effects of MD2i against cardiac I/R injury in rats.

Methods

Rats were divided into either a sham (n=6) or cardiac I/R group (n=72). Rats in the I/R group received one of the following 6 treatments (n=12 each) at the onset of reperfusion: vehicle, MD2i at 20 and 40 mg/kg, NAC at 75 and 150 mg/kg, and combined MD2i 20 mg/kg with NAC 150 mg/kg. Left ventricular (LV) function, infarct size, arrhythmia score, and cardiac mitochondrial function and dynamics were determined.

Results

Myocardial infarction, LV dysfunction, and cardiac arrhythmias were observed in rats with cardiac I/R injury, along with mitochondrial dysfunction (Fig. 1). Treatment with MD2i at either 20 or 40 mg/kg effectively reduced LV dysfunction but failed to reduce the infarct size (Fig. 1). NAC at 150 mg/kg, but not at 75 mg/kg, significantly decreased both LV dysfunction and infarct size following cardiac I/R injury (Fig. 1). However, combined treatment exerted even greater efficacy in reducing cardiac I/R injury than monotherapy, through a greater reduction of cardiac mitochondrial dysfunction and mitochondrial fission (Fig. 1). However, no benefit on reducing the arrhythmia score in all groups.

Conclusion

Combined MD2i and NAC treatment exerted a superior cardioprotective effect against cardiac I/R injury than either monotherapy regimen via an improved cardiac mitochondrial function.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. NSTDA Research Chair Grant from the National Science and Technology Development Agency Thailand2. National Research Council of Thailand

Cardiac autonomic modulation with donepezil attenuates pyroptosis and mitochondrial dysfunction, leading to improved left ventricular function in trastuzumab-induced cardiotoxicity in rats

Background

Trastuzumab (Trz)-induced cardiotoxicity (TIC) is one of the most common cardiovascular complications of targeted anticancer agents. Cardiac inflammation, cardiac mitochondrial dysfunction, oxidative stress, and cardiac autonomic dysfunction have been identified as potential mechanisms underlying the adverse effects of TIC. Although cardiac inflammation is one of the key mechanisms triggering “pyroptosis”, i.e. a new inflammatory form of programmed cell death, the association between TIC and pyroptosis is still largely unknown. Moreover, the modulation of cardiac autonomic activity using an acetylcholinesterase inhibitor (AChE) has been shown to exert cardioprotection in various heart diseases. However, the role of donepezil (DPZ), an AChE, in treating TIC has never been investigated.

Purpose

We evaluated the cardioprotective effects of DPZ on left ventricular (LV) function, cardiac mitochondrial function, and pyroptosis in rats with TIC. We hypothesised that DPZ reduces mitochondrial dysfunction and pyroptosis, leading to a reduction of LV dysfunction in TIC rats.

Methods

Fifteen male Wistar rats were randomly divided into the control group (n=5, 0.9% normal saline solution, ip) and the Trz group (n=10, 4 mg/kg/day for 7 days, ip). Trz-treated rats were subdivided into the vehicle group (n=5, drinking water, po) and the DPZ group (n=5, 5 mg/kg/day for 7 days, po). At the end of the experiment, echocardiography was performed, and the heart was removed to determine the cardiac mitochondrial function and pyroptosis.

Results

Compared with the control group, %LV ejection fraction (%LVEF) was significantly decreased in the Trz group (Fig. 1A). Trz treatment also markedly increased cardiac mitochondrial reactive oxygen species (ROS) production and mitochondrial depolarisation, as indicated by a lower red/green fluorescence intensity ratio (Fig. 1B and C, respectively). Furthermore, Trz induced pyroptosis by increasing NLR family pyrin domain containing 3 (NLRP3) expression and cleaved Gasdermin D/Gasdermin D ratio, compared to the control group (Fig, 1D–F). Notably, DPZ co-treatment potentially reduced mitochondrial ROS production, mitochondrial depolarisation, and pyroptosis (NLRP3 and cleaved Gasdermin D/Gasdermin D ratio), leading to improved %LVEF (Figure 1).

Conclusion

DPZ alleviated cardiac dysfunction in TIC rats by improving mitochondrial function and reducing pyroptosis. These findings suggested that DZP could be a novel effective pharmacological intervention against TIC.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): 1. The National Science and Technology Development Agency Thailand2. The Thailand Research Fund (RGJ)

Modulation of mitochondrial dynamics rescues cognitive function in rats with 'doxorubicin-induced chemobrain' via mitigation of mitochondrial dysfunction and neuroinflammation

Doxorubicin (DOX), an effective, extensively used chemotherapeutic drug, can cause cognitive deterioration in cancer patients. The associated debilitating neurological sequelae are referred to as chemobrain. Our recent work demonstrated that Dox treatment resulted in an imbalance in mitochondrial dynamics, ultimately culminating in cognitive decline in rats. Therefore, in this study, we aim to explore the therapeutic efficacy of a pharmacological intervention, which modulates mitochondrial dynamics using a potent mitochondrial fission inhibitor (Mdivi-1) and mitochondrial fusion promoter (M1) against Dox-induced chemobrain. In the study, male Wistar rats were randomly assigned to receive either normal saline solution or six doses of Dox (3 mg·kg-1 ) via intraperitoneal injection. Then, the Dox-treated rats were intraperitoneally given either 1% DMSO as the vehicle, Mdivi-1 (1.2 mg·kg-1 ), M1 (2 mg·kg-1 ), or a combined treatment of Mdivi-1 and M1 for 30 consecutive days. Long-term learning and memory were evaluated using the novel object location task and novel object recognition task. Following euthanasia, the rat brains were dissected to enable further molecular investigation. We demonstrated that long-term treatment with mitochondrial dynamic modulators suppressed mitochondrial fission in the hippocampus following Dox treatment, leading to an improvement in brain homeostasis. Mitochondrial dynamic modulator treatments restored cognitive function in Dox-treated rats by attenuating neuroinflammation, decreasing oxidative stress, preserving synaptic integrity, reducing potential Alzheimer's related lesions, and mitigating both apoptosis and necroptosis following Dox administration. Together, our findings suggested that mitochondrial dynamics modulators protected against Dox-induced cognitive impairment by rebalancing mitochondrial homeostasis and attenuating both oxidative and inflammatory insults.

High Cardiorespiratory Fitness Protects against Molecular Impairments of Metabolism, Heart, and Brain with Higher Efficacy in Obesity-Induced Premature Aging

BACKGRUOUND

High cardiorespiratory fitness (CRF) protects against age-related diseases. However, the mechanisms mediating the protective effect of high intrinsic CRF against metabolic, cardiac, and brain impairments in non-obese versus obese conditions remain incompletely understood. We aimed to identify the mechanisms through which high intrinsic CRF protects against metabolic, cardiac, and brain impairments in non-obese versus obese untrained rats.

METHODS

Seven-week-old male Wistar rats were divided into two groups (n=8 per group) to receive either a normal diet or a highfat diet (HFD). At weeks 12 and 28, CRF, carbohydrate and fatty acid oxidation, cardiac function, and metabolic parameters were evaluated. At week 28, behavior tests were performed. At the end of week 28, rats were euthanized to collect heart and brain samples for molecular studies.

RESULTS

The obese rats exhibited higher values for aging-related parameters than the non-obese rats, indicating that they experienced obesity-induced premature aging. High baseline CRF levels were positively correlated with several favorable metabolic, cardiac, and brain parameters at follow-up. Specifically, the protective effects of high CRF against metabolic, cardiac, and brain impairments were mediated by the modulation of body weight and composition, the lipid profile, substrate oxidation, mitochondrial function, insulin signaling, autophagy, apoptosis, inflammation, oxidative stress, cardiac function, neurogenesis, blood-brain barrier, synaptic function, accumulation of Alzheimer's disease-related proteins, and cognition. Interestingly, this effect was more obvious in HFD-fed rats.

CONCLUSION

The protective effect of high CRF is mediated by the modulation of several mechanisms. These effects exhibit greater efficacy under conditions of obesity-induced premature aging.

Ranolazine alleviated cardiac/brain dysfunction in doxorubicin-treated rats

Doxorubicin (Dox), a powerful chemotherapeutic agent, has been shown to cause cardiotoxicity and neurotoxicity. Ranolazine, a drug that is commonly used to treat patients with chronic angina, has been shown to reduce toxicity from Dox therapy. Therefore, the present study aims to investigate the mechanisms behind the protective effects of ranolazine on the heart and brain in Dox-treatment. Twenty-four male Wistar rats received 6 doses of either 0.9% normal saline (0.9% NSS, i.p., n = 8) or Dox (3 mg/kg, i.p., n = 16). All Dox-treated rats were assigned into 2 groups to receive vehicle (0.9% NSS, orally; n = 8) or ranolazine (305 mg/kg/day, orally; n = 8) for 30 consecutive days. Following the treatments, left ventricular (LV) function and cognition were determined. Animals were euthanized, then the heart and brain were collected for further analysis. Dox induced systemic oxidative stress/inflammation, and cardiac injury evidenced by mitochondrial dysfunction, mitochondrial dynamic imbalance, and apoptosis, resulting in LV dysfunction. Ranolazine significantly improved LV function via attenuating cardiac injury. Dox also caused brain pathologies as indicated by increased brain inflammation, impaired blood-brain barrier integrity, brain mitochondrial dysfunction, microglial dysmorphology, hippocampal dysplasticity, and increased apoptosis, resulting in cognitive decline. Ranolazine exerted neuroprotective effects by suppressing brain pathologies and restoring cognitive function. These findings suggest that ranolazine has a potential role in cardio- and neuro-protection against chemotherapy.

An apoptosis inhibitor suppresses microglial and astrocytic activation after cardiac ischemia/reperfusion injury

OBJECTIVE

Microglial hyperactivation and apoptosis were observed following myocardial infarction and ischemia reperfusion (I/R) injury. This study aimed to test the hypothesis that the apoptosis inhibitor, Z-VAD, attenuates microglial and astrocytic hyperactivation and brain inflammation in rats with cardiac I/R injury.

MATERIALS AND METHODS

Rats were subjected to either sham or cardiac I/R operation (30 min-ischemia followed by 120-min reperfusion), rats in the cardiac I/R group were given either normal saline solution or Z-VAD at 3.3 mg/kg via intravenous injection 15 min prior to cardiac ischemia. Left ventricular ejection fraction (% LVEF) was determined during the cardiac I/R protocol. The brain tissues were removed and used to determine brain apoptosis, brain inflammation, microglial and astrocyte morphology.

RESULTS

Cardiac dysfunction was observed in rats with cardiac I/R injury as indicated by decreased %LVEF. In the brain, we found brain apoptosis, brain inflammation, microglia hyperactivation, and reactive astrogliosis occurred following cardiac I/R injury. Pretreatment with Z-VAD effectively increased %LVEF, reduced brain apoptosis, attenuated brain inflammation by decreasing IL-1β mRNA levels, suppressed microglial and astrocytic hyperactivation and proliferation after cardiac I/R injury.

CONCLUSION

Z-VAD exerts neuroprotective effects against cardiac I/R injury not only targeting apoptosis but also microglial and astrocyte activation.

Evaluation of CD44s, CD44v6, CXCR2, CXCL1, and IL-1β in Benign and Malignant Tumors of Salivary Glands

BACKGROUND

Several studies have reported an association between high expression of CD44 in different types of cancer. However, no study has reported a link among CD44 expression, other biomarkers, and the aggressiveness of salivary gland tumors.

METHODS

A total of 38 specimens were obtained from non-tumorous salivary glands, benign and malignant tumors in salivary glands. Immunohistochemical analyses of CD44s, CD44v6, IL-1β, CXCL1, and CXCR2 were performed, and the area of positive cells was assessed.

RESULTS

We found that both CD44s and CXCR2 expression were increased in the benign and malignant groups. CD44v6 was also increased in both groups, but it had the highest level in the malignant group. IL-1β was the only biomarker that increased significantly in the malignant group in comparison to the other two groups.

CONCLUSIONS

CD44s, CD44v6, CXCR2, and IL-1β expressions were found to be higher in salivary gland tumors. However, IL-1β alone may play a crucial role in the aggressiveness of salivary gland tumors as this cytokine was expressed only in the malignant group with high expression associated with high-grade malignancy.

Therapeutic potential of a single-dose melatonin in the attenuation of cardiac ischemia/reperfusion injury in prediabetic obese rats

Although acute melatonin treatment effectively reduces cardiac ischemia/reperfusion (I/R) injury in lean rats by modulating melatonin receptor 2 (MT2), there is no information regarding the temporal effects of melatonin administration during cardiac I/R injury in prediabetic obese rats. Prediabetic obese rats induced by chronic consumption of a high-fat diet (HFD) were used. The rats underwent a cardiac I/R surgical procedure (30-min of ischemia, followed by 120-min of reperfusion) and were randomly assigned to receive either vehicle or melatonin treatment. In the melatonin group, rats were divided into 3 different subgroups: (1) pretreatment, (2) treatment during ischemic period, (3) treatment at the reperfusion onset. In the pretreatment subgroup either a nonspecific MT blocker (Luzindole) or specific MT2 blocker (4-PPDOT) was also given to the rats prior to melatonin treatment. Pretreatment with melatonin (10 mg/kg) effectively reduced cardiac I/R injury by reducing infarct size, arrhythmia, and LV dysfunction. Reduction in impaired mitochondrial function, mitochondrial dynamic balance, oxidative stress, defective autophagy, and apoptosis were observed in rats pretreated with melatonin. Unfortunately, the cardioprotective benefits were not observed when 10-mg/kg of melatonin was acutely administered to the rats after cardiac ischemia. Thus, we increased the dose of melatonin to 20 mg/kg, and it was administered to the rats during ischemia or at the onset of reperfusion. The results showed that 20-mg/kg of melatonin effectively reduced cardiac I/R injury to a similar extent to the 10-mg/kg pretreatment regimen. The MT2 blocker inhibited the protective effects of melatonin. Acute melatonin treatment during cardiac I/R injury exerted protective effects in prediabetic obese rats. However, a higher dose of melatonin is required when given after the onset of cardiac ischemia. These effects of melatonin were mainly mediated through activation of MT2.

Chronic Cortical Inflammation, Cognitive Impairment, and Immune Reactivity Associated with Diffuse Brain Injury Are Ameliorated by Forced Turnover of Microglia

Traumatic brain injury (TBI) is associated with an increased risk of cognitive, psychiatric, and neurodegenerative complications that may develop after injury. Increased microglial reactivity following TBI may underlie chronic neuroinflammation, neuropathology, and exaggerated responses to immune challenges. Therefore, the goal of this study was to force turnover of trauma-associated microglia that develop after diffuse TBI and determine whether this alleviated chronic inflammation, improved functional recovery and attenuated reduced immune reactivity to lipopolysaccharide (LPS) challenge. Male mice received a midline fluid percussion injury (mFPI) and 7 d later were subjected to a forced microglia turnover paradigm using CSF1R antagonism (PLX5622). At 30 d postinjury (dpi), cortical gene expression, dendritic complexity, myelin content, neuronal connectivity, cognition, and immune reactivity were assessed. Myriad neuropathology-related genes were increased 30 dpi in the cortex, and 90% of these gene changes were reversed by microglial turnover. Reduced neuronal connectivity was evident 30 dpi and these deficits were attenuated by microglial turnover. TBI-associated dendritic remodeling and myelin alterations, however, remained 30 dpi independent of microglial turnover. In assessments of functional recovery, increased depressive-like behavior, and cognitive impairment 30 dpi were ameliorated by microglia turnover. To investigate microglial priming and reactivity 30 dpi, mice were injected intraperitoneally with LPS. This immune challenge caused prolonged lethargy, sickness behavior, and microglial reactivity in the TBI mice. These extended complications with LPS in TBI mice were prevented by microglia turnover. Collectively, microglial turnover 7 dpi alleviated behavioral and cognitive impairments associated with microglial priming and immune reactivity 30 dpi.SIGNIFICANCE STATEMENT A striking feature of traumatic brain injury (TBI), even mild injuries, is that over 70% of individuals have long-term neuropsychiatric complications. Chronic inflammatory processes are implicated in the pathology of these complications and these issues can be exaggerated by immune challenge. Therefore, our goal was to force the turnover of microglia 7 d after TBI. This subacute 7 d postinjury (dpi) time point is a critical transitional period in the shift toward chronic inflammatory processes and microglia priming. This forced microglia turnover intervention in mice attenuated the deficits in behavior and cognition 30 dpi. Moreover, microglia priming and immune reactivity after TBI were also reduced with microglia turnover. Therefore, microglia represent therapeutic targets after TBI to reduce persistent neuroinflammation and improve recovery.

Acetylcholine receptor agonists provide cardioprotection in doxorubicin-induced cardiotoxicity via modulating muscarinic M2 and α7 nicotinic receptor expression

The balance between cardiac sympathetic and parasympathetic activities has been intricately linked to mitochondrial function, cellular oxidative status, and immunomodulation in healthy and diseased myocardium. Cardiac autonomic neuropathy, along with the associated mitochondrial and cellular dysfunction, is an important pathophysiological feature of doxorubicin-induced cardiotoxicity (DIC). We tested the hypothesis that autonomic modulation by activation of acetylcholine receptors (AChR) effectively attenuates DIC. Rats were divided into control (0.9% sodium chloride solution) and doxorubicin groups (DOX, 3 mg/kg/d, 6 doses). Rats in the DOX group were equally subdivided into 4 interventional groups and treated for 30 days: vehicle, α7 nicotinic receptor agonist (PNU: PNU-282987, 3 mg/kg/d), muscarinic receptor agonist (BET: bethanechol, 12 mg/kg/d), and combined α7nAChR and mAChR agonists group (COM). Cardiac biochemical and functional analyses were done. The results show that AChR agonists protected the heart against DIC via improving mitochondrial and cardiac function, which was accompanied by reducing mitochondrial oxidative damage, apoptosis, and inflammation. Strikingly, PNU and BET exerted cardioprotection through different molecular pathways. PNU-mediated α7nAChR activation promoted mitochondrial fusion via upregulation of Mfn1-2 and attenuated DOX-induced autophagy. Contrarily, activation of mAChR by BET attenuated mitochondrial fission and mitophagy. The in vitro experiments confirmed the cytoprotective effects of AChR activation in DOX-treated H9c2 cells without compromising the anticancer effect of DOX in cancer cells. In conclusion, α7nAChR and mAChR agonists exerted cardioprotection against DIC via rebalancing autonomic function, improving mitochondrial function, reducing oxidative stress, and decreased cardiomyocyte apoptosis and inflammation, leading to improved cardiac function.

Mild cognitive impairment occurs in rats during the early remodeling phase of myocardial infarction

Cognitive impairment is a common health problem among people with heart failure (HF). Increases in oxidative stress, brain inflammation, and microglial hyperactivity have been reported in preclinical models of myocardial infarction (MI)-induced HF. We tested the hypothesis that oxidative stress, brain inflammation, mitochondrial dysfunction, and cell death participate in cognitive impairment in the early remodeling phase of MI. Rats underwent either a sham or permanent left anterior descending coronary ligation to induce MI. 1-week post-operation, MI rats with % left ventricular ejection fraction (%LVEF) ≥50 were assigned as a HF with preserved ejection fraction (HFpEF) group and MI rats with %LVEF<50 were assigned as a HF with reduced ejection fraction (HFrEF) group. Cognitive function and biochemical markers were assessed at week 5. The mean value of %LVEF in HFpEF and HFrEF were 63.62±8.33 and 42.83±3.93 respectively, which were lower than in the sham group, suggesting that these rats developed MI with cardiac dysfunction. Hippocampal dependent cognitive impairment was observed in MI rats. Serum, brain, and mitochondrial oxidative stress were all increased in MI rats, along with apoptosis, resulting in dendritic spine loss. However, brain inflammation and AD proteins did not change. In conclusion, during the early remodeling phase of MI, a high level of oxidative stress appears to be a major contributor of cellular damage which is associated with mild cognitive impairment. However, the severity of MI, as evidenced by the %LVEF, was not associated with the degree of cognitive impairment.

Pharmacological Targeting of Mitochondrial Fission and Fusion Alleviates Cognitive Impairment and Brain Pathologies in Pre-diabetic Rats

It has recently been accepted that long-term high-fat diet (HFD) intake is a significant possible cause for prediabetes and cognitive and brain dysfunction through the disruption of brain mitochondrial function and dynamic balance. Although modulation of mitochondrial dynamics by inhibiting fission and promoting fusion has been shown to reduce the morbidity and mortality associated with a variety of chronic diseases, the impact of either pharmacological inhibition of mitochondrial fission (Mdivi-1) or stimulation of fusion (M1) on brain function in HFD-induced prediabetic models has never been studied. Thirty-two male Wistar rats were separated into 2 groups and fed either a normal diet (ND, n = 8) or HFD (n = 24) for 14 weeks. At week 12, HFD-fed rats were divided into 3 subgroups (n = 8/subgroup) and given an intraperitoneal injection of either saline, Mdivi-1 (1.2 mg/kg/day), or M1 (2 mg/kg/day) for 2 weeks. Cognitive function and metabolic parameters were determined toward the end of the protocol. The rats then were euthanized, and the brain was immediately removed in order to evaluate brain mitochondrial function and mitochondrial dynamics. HFD-fed rats experienced prediabetes, evidenced by elevated plasma insulin and the HOMA index, impaired mitochondrial function in the brain, altered dynamic regulation, and cognitive impairment were also found. Mdivi-1 and M1 treatment exerted neuroprotection to a similar extent by improving metabolic parameters, balancing mitochondrial dynamics, and reducing mitochondrial dysfunction, resulting in a gradual increase in cognitive function. Therefore, pharmacological targeting of mitochondrial fission and fusion protected the brain against chronic HFD-induced prediabetes.

Therapeutic potentials of cell death inhibitors in rats with cardiac ischaemia/reperfusion injury

Growing evidence demonstrated that cell death pathways including ferroptosis, apoptosis and necroptosis contribute to cardiac ischaemia/reperfusion (I/R) injury. We hypothesized that ferroptosis, apoptosis and necroptosis contribute differently to myocardial damage during acute cardiac I/R injury. Rats underwent cardiac I/R or sham operation. I/R-operated rats were divided into 4 groups: vehicle, apoptosis (Z-vad), ferroptosis (Fer-1) and necroptosis (Nec-1) inhibition. Rats in each cell death inhibitor group were subdivided into 3 different dose regimens: low, medium and high. Infarct size, left ventricular (LV) function, arrhythmias and molecular mechanism were investigated. Cardiac I/R caused myocardial infarction, LV dysfunction, arrhythmias, mitochondrial dysfunction, mitochondrial dynamic imbalance, inflammation, apoptosis and ferroptosis. Infarct size, LV dysfunction, mitochondrial dysfunction, apoptosis and ferroptosis were all reduced to a similar extent in rats treated with Z-vad (low and medium doses) or Fer-1 (medium and high doses). Fer-1 treatment also reduced mitochondrial dynamic imbalance and inflammation. No evidence of necroptosis was found in association with acute I/R injury, therefore Nec-1 treatment could not be assessed. Apoptosis and ferroptosis, not necroptosis, contributed to myocardial damage in acute I/R injury. Inhibitors of these 2 pathways provided effective cardioprotection in rats with I/R injury though modulation of mitochondrial function and attenuated apoptosis and ferroptosis.

Effectiveness of high cardiorespiratory fitness in cardiometabolic protection in prediabetic rats

Background

Caloric restriction and exercise are lifestyle interventions that effectively attenuate cardiometabolic impairment. However, cardioprotective effects of long-term lifestyle interventions and short-term lifestyle interventions followed by weight maintenance in prediabetes have never been compared. High cardiorespiratory fitness (CRF) has been shown to provide protection against prediabetes and cardiovascular diseases, however, the interactions between CRF, prediabetes, caloric restriction, and exercise on cardiometabolic health has never been investigated.

Methods

Seven-week-old male Wistar rats were fed with either a normal diet (ND; n = 6) or a high-fat diet (HFD; n = 30) to induce prediabetes for 12 weeks. Baseline CRF and cardiometabolic parameters were determined at this timepoint. The ND-fed rats were fed continuously with a ND for 16 more weeks. The HFD-fed rats were divided into 5 groups (n = 6/group) to receive one of the following: (1) a HFD without any intervention for 16 weeks, (2) 40% caloric restriction for 6 weeks followed by an ad libitum ND for 10 weeks, (3) 40% caloric restriction for 16 weeks, (4) a HFD plus an exercise training program for 6 weeks followed by a ND without exercise for 10 weeks, or (5) a HFD plus an exercise training program for 16 weeks. At the end of the interventions, CRF and cardiometabolic parameters were re-assessed. Then, all rats were euthanized and heart tissues were collected.

Results

Either short-term caloric restriction or exercise followed by weight maintenance ameliorated cardiometabolic impairment in prediabetes, as indicated by increased insulin sensitivity, improved blood lipid profile, improved mitochondrial function and oxidative phosphorylation, reduced oxidative stress and inflammation, and improved cardiac function. However, these benefits were not as effective as those of either long-term caloric restriction or exercise. Interestingly, high-level baseline CRF was correlated with favorable cardiac and metabolic profiles at follow-up in prediabetic rats, both with and without lifestyle interventions.

Conclusions

Short-term lifestyle modification followed by weight maintenance improves cardiometabolic health in prediabetes. High CRF exerted protection against cardiometabolic impairment in prediabetes, both with and without lifestyle modification. These findings suggest that targeting the enhancement of CRF may contribute to the more effective treatment of prediabetes-induced cardiometabolic impairment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00458-9.

Profiles of gut microbiota in obese-insulin-resistant rats treated with biotics

PURPOSE

Our previous studies demonstrated the beneficial effects of the probiotic Lactobacillus paracasei HII01, prebiotic xylooligosaccharide (XOS), and synbiotics on several parameters in high-fat diet (HFD)-induced obese rats. However, the gut microbiota composition in these rats has not been investigated. Therefore, this study aimed to investigate the impact of biotic therapies on gut microbiota in HFD-induced obese-insulin-resistant rats.

METHODS

Male Wistar rats were fed with a normal diet (ND, n = 5) and a HFD (n = 20) for 24 weeks. At week 13, HFD-fed rats were given either a probiotic (L. paracasei, HF-Pro, n = 5), prebiotic (XOS, HF-Pre, n = 5), synbiotic (XOS + L. paracasei, HF-Syn, n = 5), or vehicle (HF-V, n = 5) for 12 weeks. ND-fed rats received vehicle (ND-V, n = 5). At week 24, all rats were decapitated, and metabolic parameters and gut microbiota were analyzed.

RESULTS

HF-V rats developed an obese-insulin-resistant condition as indicated by impaired metabolic parameters. The prebiotic and synbiotic restored those metabolic parameters to the same level of ND-V rats. The gut microbiota composition of ND-V and HF-V rats differed as indicated by beta diversity. Verrucomicrobia in ND-V rats and Firmicutes and Proteobacteria in HF-V rats were dominant. Interestingly, Verrucomicrobia was also prominent in the HF-Syn rats. HF-Pre rats showed a distinct gut microbiota the predominant family being Ruminococcaceae.

CONCLUSION

The changes in gut microbiota after HFD consumption included increased Firmicutes and Proteobacteria. The treatment with the prebiotic and synbiotic showed an association with the increase in Ruminococcaceae and Verrucomicrobia, respectively. These changes in gut microbiota due to biotics may mediate the beneficial effects on metabolic parameters.