Pharmacological preconditioning by milrinone: Memory preserving and neuroprotective effect in ischemia-reperfusion injury in mice

Neuroprotective Effects of Milrinone on Acute Traumatic Brain Injury

BACKGROUND

Traumatic brain injury is still an important health problem worldwide. Traumatic brain injury not only causes direct mechanical damage to the brain but also induces biochemical changes that lead to secondary nerve cell loss. In this study, we investigated the neuroprotective effect of milrinone after traumatic brain injury (TBI) in a rat model.

METHODS

Forty male Wistar albino rats, were used. Rats were divided into 4 groups: 1) sham, 2) TBI, 3) TBI + Ringers, and 4) TBI + Milrinone. In group 1 (sham), only craniotomy was performed. In group 2 (TBI), TBI was performed after craniotomy. In group 3 (TBI + Ringer), TBI was performed after craniotomy and intraperitoneal Ringers solution was given immediately afterward. Group 4 (TBI + Milrinone), TBI was performed after craniotomy, and milrinone was given 1.0 mg/kg milrinone intraperitoneally directly (0.5 mg/kg milrinone intraperitoneally again 24 hours, 48 hours, and 72 hours after trauma). Tests were performed for neurological and neurobehavioral functions. Immunohistochemistry and histopathology studies were performed.

RESULTS

In group 4 compared with group 2 and group 3 groups, tests for neurological functions and neurobehavioral functions were significantly better. In the milrinone treatment used in group 4, plasma and brain tissue tumor necrosis factor, 8-OH 2-deoxyguanosine , and interleukin 6 levels were significantly decreased, and increased plasma and tissue IL-10 levels were detected. Histopathological spinal cord injury and apoptotic index increased in groups 2 and 3, while significantly decreasing in group 4.

CONCLUSIONS

This study shows for the first time that the anti-inflammatory, antioxidant and antiapoptotic properties of milrinone may be neuroprotective after TBI.

The Role of Ruthenium Compounds in Neurological Diseases: A Minireview

Ruthenium (Ru) compounds, nitric oxide donors in biological systems, have emerged as a promising therapeutical alternative to conventional drugs in anticancer chemotherapy and as a potential neuroprotective agent, with less cytotoxic effects. This minireview summarizes promising studies with ruthenium complexes and their roles in cancer, neuroinflammation, neurovascular, and neurodegenerative diseases. The up-to-date evidence supports that ruthenium-based compounds have beneficial effects against gliomas, and other types of brain cancers, reduce motor symptoms in models of cerebral ischemia-reperfusion, and may act in the control of nociceptive and inflammatory events, such as seen in early Alzheimer's disease. More studies are needed to fill many current knowledge gaps about the intricate and complex ruthenium biological effects and therapeutic-related mechanisms, stimulating further research. Significance Statement In our minireview, we summarize interesting studies addressing the role of ruthenium compounds on neurological illnesses, focusing on brain cancer, neurovascular and neurodegenerative diseases. No such review is available in the literature.

Nitrile-containing pharmaceuticals: target, mechanism of action, and their SAR studies

The nitrile group is an important functional group widely found in both pharmaceutical agents and natural products. More than 30 nitrile-containing pharmaceuticals have been approved by the FDA for the management of a broad range of clinical conditions in the last few decades. Incorporation of a nitrile group into lead compounds has gradually become a promising strategy in rational drug design as it can bring additional benefits including enhanced binding affinity to the target, improved pharmacokinetic profile of parent drugs, and reduced drug resistance. This paper reviews the existing drugs with a nitrile moiety that have been approved or in clinical trials, involving their targets, molecular mechanism of pharmacology and SAR studies, and classifies them into different categories based on their clinical usages.

Milrinone ameliorates ischaemia-reperfusion injury in experimental testicular torsion/detorsion rat model

This experimental study aims to evaluate the efficacy of milrinone against ischaemia-reperfusion injury due to testicular torsion/detorsion. Group 1 was defined as the control group. Testicular torsion/detorsion model was performed in Group 2. Group 3 had similar procedures to the rats in Group 2. In addition, 0.5 mg/kg of milrinone was administered intraperitoneally immediately after testicular torsion in Group 3. Histopathological examinations indicated a dramatic improvement in terms of inflammation, haemorrhage, oedema, congestion, Cosentino and Johnson scores in Group 3 compared to Group 2 (p = .037, p = .045, p = .018, p = .040, p = .033 and p = .03 respectively). Blood biochemical analyses, superoxide dismutase (SOD), glutathione peroxidase (GSH-px) activity and total antioxidant status (TAS) levels increased significantly in Group 3 compared to Group 2 (p = .001, p = .024 and p < .001). Malondialdehyde (MDA), protein carbonyl (PC), interleukin 1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and total oxidant status (TOS) levels decreased in Group 3 compared to Group 2 (p = .001, p = .018, p < .001, p = .036 and p = .002 respectively). Tissue biochemical analyses determined an increase in SOD and GSH-px activity in Group 3 compared to Group 2, while PC and MDA levels were reduced (p = .001, p < .001, p = .038 and p < .001 respectively). Milrinone attenuates ischaemia-reperfusion injury that causes highly harmful effects due to testicular torsion/detorsion.

Intravenous milrinone for treatment of delayed cerebral ischaemia following subarachnoid haemorrhage: a pooled systematic review

Small trials have demonstrated promising results utilising intravenous milrinone for the treatment of delayed cerebral ischaemia (DCI) after subarachnoid haemorrhage (SAH). Here we summarise and contextualise the literature and discuss the future directions of intravenous milrinone for DCI. A systematic, pooled analysis of literature was performed in accordance with the PRISMA statement. Methodological rigour was analysed using the MINORS criteria. Extracted data included patient population; treatment protocol; and clinical, radiological, and functional outcome. The primary outcome was clinical resolution of DCI. Eight hundred eighteen patients from 10 single-centre, observational studies were identified. Half (n = 5) of the studies were prospective and all were at high risk of bias. Mean age was 52 years, and females (69%) outnumbered males. There was a similar proportion of low-grade (WFNS 1-2) (49.7%) and high-grade (WFNS 3-5) (50.3%) SAH. Intravenous milrinone was administered to 523/818 (63.9%) participants. Clinical resolution of DCI was achieved in 375/424 (88%), with similar rates demonstrated with intravenous (291/330, 88%) and combined intra-arterial-intravenous (84/94, 89%) therapy. Angiographic response was seen in 165/234 (71%) receiving intravenous milrinone. Hypotension (70/303, 23%) and hypokalaemia (31/287, 11%) were common drug effects. Four cases (0.5%) of drug intolerance occurred. Good functional outcome was achieved in 271/364 (74%) patients. Cerebral infarction attributable to DCI occurred in 47/250 (19%), with lower rates in asymptomatic spasm. Intravenous milrinone is a safe and feasible therapy for DCI. A signal for efficacy is demonstrated in small, low-quality trials. Future research should endeavour to establish the optimal protocol and dose, prior to a phase-3 study.

Milrinone Ameliorates the Neuroinflammation and Memory Function of Alzheimer's Disease in an APP/PS1 Mouse Model

PURPOSE

Alzheimer's disease (AD) is a complex neurodegenerative disorder, which is characterized by memory loss and cognitive deficits. The neuroprotective role of milrinone on the injury of spinal cord or cerebral ischemia-reperfusion has been confirmed. However, the accurate function of milrinone on AD pathogeny is still unclear.

METHODS

APP/PS1 transgenic mouse was used to explore the role of milrinone in behaviour tests, and the effects on histopathologic features of AD such as the formation of neuronal amyloid-β (Aβ) plaque, microglial activation, tau protein hyperphosphorylation, oxidative stress, and neuroinflammation. Lipopolysaccharide (LPS)/Aβ-treated BV-2 cells were used to understand the anti-inflammation mechanism of milrinone on AD in vitro.

RESULTS

Our in vivo results showed that milrinone ameliorates the memory functions of AD mice. Meanwhile, milrinone reduced Aβ deposits, repressed microglial activation and tau protein hyperphosphorylation, attenuated the oxidative stress, and decreased the levels of inflammatory cytokines. The in vitro results demonstrated that milrinone could inhibit the secretion of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α via regulation of NLRP3 inflammasomes and TLR4/MyD88/NF-κB signalling pathway.

CONCLUSION

Overall, milrinone could ameliorate the memory loss and cognitive deficits through repressing the multiple pathological processes of AD, suggesting that milrinone may be an underlying and effective drug for treating AD clinically.

Development of a Rapid Mass Spectrometric Determination of AMP and Cyclic AMP for PDE3 Activity Study: Application and Computational Analysis for Evaluating the Effect of a Novel 2-oxo-1,2-dihydropyridine-3-carbonitrile Derivative as PDE-3 Inhibitor

A simple, quick, easy and cheap tandem mass spectrometry (MS/MS) method for the determination of adenosine monophosphate (AMP) and cyclic adenosine monophosphate (cAMP) has been newly developed. This novel MS/MS method was applied for the evaluation of the inhibitory effect of a novel 2-oxo-1,2-dihydropyridine-3-carbonitrile derivative, also named DF492, on PDE3 enzyme activity in comparison to its parent drug milrinone. Molecule DF492, with an IC₅₀ of 409.5 nM, showed an inhibition of PDE3 greater than milrinone (IC₅₀ = 703.1 nM). To explain the inhibitory potential of DF492, molecular docking studies toward the human PDE3A were carried out with the aim of predicting the binding mode of DF492. The presence of different bulkier decorating fragments in DF492 was pursued to shift affinity of this novel molecule toward PDE3A compared to milrinone in accordance with both the theoretical and experimental results. The described mass spectrometric approach could have a wider potential use in kinetic and biomedical studies and could be applied for the determination of other phosphodiesterase inhibitor molecules.

Pain attenuating actions of vincristinet-preconditioning in chemotherapeutic agent-induced neuropathic pain: key involvement of T-type calcium channels

Preconditioning is a well-documented strategy that induces hepatic protection, renal protection, cardioprotection, and neuroprotection but its mechanism still remains to be elucidated. Hence, the present study investigated the protective mechanism underlying pain attenuating effects of vincristine-preconditioning in chemotherapeutic agent-induced neuropathic pain. Neuropathic pain was induced by administration of vincristine (50 µg/kg, i.p.) for 10 days in rats. Vincristine-preconditioning was induced by administration of vincristine (2, 5, and 10 µg/kg, i.p) for 5 days before administration of pain-inducing dose of vincristine (50 µg/kg, i.p.). Vincristine-preconditioning (10 µg/kg, i.p) for 5 days significantly reduced vincristine (50 µg/kg, i.p.) induced pain-related behaviors including paw cold allodynia, mechanical hyperalgesia, and heat hyperalgesia. However, vincristine (2 and 5 µg/kg, i.p) did not significantly ameliorate the vincristine (50 µg/kg, i.p.) induced neuropathic pain in rats. Furthermore, to explore the involvement of calcium channels in pain attenuating mechanism of vincristine-preconditioning, T-type calcium channel blocker, ethosuximide (100 and 200 mg/kg, i.p.) and L-type calcium channel blocker, amlodipine (5 and 10 mg/kg, i.p.) were used. Pretreatment with T-type calcium channel blocker, ethosuximide significantly abolished vincristine-preconditioning-induced protective effect. However, pretreatment with L-type calcium channel blocker, amlodipine did not alter vincristine-preconditioning-induced pain-related behaviors. This indicates that vincristine-preconditioning has protective effect on pain-related parameters due to opening of calcium channels, particularly T-type calcium channels that lead to entry of small magnitude of intracellular calcium through these channels and prevent the deleterious effects of high-dose vincristine.

Milrinone-Induced Pharmacological Preconditioning in Cardioprotection: Hints for a Role of Mitochondrial Mechanisms

The activation of mitochondrial calcium-sensitive potassium (mBK_Ca) channels is crucially involved in cardioprotection induced by preconditioning. For milrinone (Mil)-induced preconditioning, the involvement of mBK_Ca-channels and further mitochondrial signaling is unknown. We hypothesize that (1) Mil-induced preconditioning is concentration-dependent and (2) that the activation of mBK_Ca-channels, release of reactive oxygen species (ROS), and the mitochondrial permeability transition pore (mPTP) could be involved. Isolated hearts of male Wistar rats were perfused with Krebs-Henseleit buffer and underwent 33 min of ischemia followed by 60 min of reperfusion. For determination of a concentration-dependent effect of Mil, hearts were perfused with different concentrations of Mil (0.3–10 µM) over 10 min before ischemia. In a second set of experiments, in addition to controls, hearts were pretreated with the lowest protective concentration of 1 µM Mil either alone or combined with the mBK_Ca-channel blocker paxilline (Pax + Mil), or paxilline alone (Pax). In additional groups, Mil was administered with and without the ROS scavenger N-2-mercaptopropionylglycine (MPG + Mil, MPG) or the mPTP inhibitor cyclosporine A (MPG + Mil + CsA, CsA + Mil), respectively. Infarct sizes were determined by triphenyltetrazolium chloride (TTC) staining. The lowest and most cardioprotective concentration was 1 µM Mil (Mil 1: 32 ± 6%; p < 0.05 vs. Con: 63 ± 8% and Mil 0.3: 49 ± 6%). Pax and MPG blocked the infarct size reduction of Mil (Pax + Mil: 53 ± 6%, MPG + Mil: 59 ± 7%; p < 0.05 vs. Mil: 34 ± 6%) without having an effect on infarct size when administered alone (Pax: 53 ± 7%, MPG: 58 ± 5%; ns vs. Con). The combined administration of CsA completely restored the MPG-inhibited cardioprotection of Mil (MPG + Mil + CsA: 35 ± 7%, p < 0.05 vs. MPG + Mil). Milrinone concentration-dependently induces preconditioning. Cardioprotection is mediated by the activation of mBK_Ca-channels, release of ROS and mPTP inhibition.

Long-term cilostazol administration prevents age-related decline of hippocampus-dependent memory in mice

Phosphodiesterases (PDEs) are enzymes that hydrolyze and inactivate 3', 5'-cyclic adenosine monophosphate (cAMP) and/or 3', 5'-cyclic guanosine monophosphate (cGMP). The regulation of intracellular signaling pathways mediated by cyclic nucleotides is imperative to synaptic plasticity and memory in animals. Because PDEs play an important role in this regulation, PDE inhibitors are considered as candidate compounds for treating cognitive and memory disorders. In the present study, we tested whether cilostazol, a selective PDE3 inhibitor, prevents the cognitive deterioration that occurs during the course of normal aging in mice. Ten months of cilostazol administration (1.5%) in 13-month-old mice improved spatial memory when tested at 23 months of age. First, it prevented the decline in the ability of these aged mice to recognize a change in an object's location in the object recognition task. Second, spatial memory of these cilostazol-treated aged mice in the Morris water maze was comparable to that of untreated middle-aged mice (13 months old). Cilostazol administration had no effect on the emotional states and physical ability of aged mice. Thus, long-term cilostazol administration prevented hippocampus-dependent memory decline in aged mice, allowing them to achieve a level of cognitive performance similar to middle-aged mice and without negative behavioral side effects. Considering its well-established safety in other medical contexts, cilostazol may be a potential therapeutic candidate drug for staving off cognitive decline in the aging human population.

Investigation of the role of non-selective calcium channel blocker (flunarizine) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice

The present study was designed to investigate the role of flunarizine (a non-selective calcium channel blocker) on cerebral ischemic-reperfusion associated cognitive dysfunction in aged mice. Bilateral carotid artery occlusion of 12min followed by reperfusion for 24h was given to induce cerebral injury in male Swiss mice. The assessment of learning & memory was performed by Morris water maze test; motor in-coordination was evaluated by rota rod, lateral push and inclined beam walking tests; cerebral infarct size was quantified by triphenyltetrazolium chloride staining. In addition, reduced glutathione (GSH), total calcium and acetylcholinesterase (AChE) activity were also estimated in aged brain tissue. Donepezil treated group served as a positive control in this study. Ischemia reperfusion (I/R) injury produced significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Further, I/R injury also produced significant increase in levels of total calcium, AChE activity and decrease in GSH levels. Pretreatment of flunarizine significantly attenuated I/R induced infarct size, behavioral and biochemical changes. Hence, it may be concluded that, a non-selective calcium channel blocker can be useful in I/R associated cognitive dysfunction due to its anti-oxidant, anti-infarct and modulatory actions of neurotransmitters & calcium channels.

Inhibition of phosphodiesterase 4 reduces ethanol intake and preference in C57BL/6J mice

Some anti-inflammatory medications reduce alcohol consumption in rodent models. Inhibition of phosphodiesterases (PDE) increases cAMP and reduces inflammatory signaling. Rolipram, an inhibitor of PDE4, markedly reduced ethanol intake and preference in mice and reduced ethanol seeking and consumption in alcohol-preferring fawn-hooded rats (Hu et al., 2011; Wen et al., 2012). To determine if these effects were specific for PDE4, we compared nine PDE inhibitors with different subtype selectivity: propentofylline (nonspecific), vinpocetine (PDE1), olprinone, milrinone (PDE3), zaprinast (PDE5), rolipram, mesopram, piclamilast, and CDP840 (PDE4). Alcohol intake was measured in C57BL/6J male mice using 24-h two-bottle choice and two-bottle choice with limited (3-h) access to alcohol. Only the selective PDE4 inhibitors reduced ethanol intake and preference in the 24-h two-bottle choice test. For rolipram, piclamilast, and CDP840, this effect was observed after the first 6 h but not after the next 18 h. Mesopram, however, produced a long-lasting reduction of ethanol intake and preference. In the limited access test, rolipram, piclamilast, and mesopram reduced ethanol consumption and total fluid intake and did not change preference for ethanol, whereas CDP840 reduced both consumption and preference without altering total fluid intake. Our results provide novel evidence for a selective role of PDE4 in regulating ethanol drinking in mice. We suggest that inhibition of PDE4 may be an unexplored target for medication development to reduce excessive alcohol consumption.

Tadalafil enhances the neuroprotective effects of ischemic postconditioning in mice, probably in a nitric oxide associated manner

This study investigates the modulatory effect of tadalafil, a selective phosphodiesterase (PDE-5) inhibitor, on the neuroprotective effects of ischemic postconditioning (iPoCo) in mice. Bilateral carotid artery occlusion (BCAO) for 12 min followed by reperfusion for 24 h was employed to produce ischemia and reperfusion induced cerebral injury. Cerebral infarct size was measured using TTC staining. Memory was assessed using the Morris water maze test. Degree of motor incoordination was evaluated using inclined beam-walking, rota-rod, and lateral push tests. Brain nitrite/nitrate, acetylcholinesterase activity, TBARS, and glutathione levels were also estimated. BCAO followed by reperfusion produced a significant increase in cerebral infarct size, brain nitrite/nitrate and TBARS levels, and acetylcholinesterase activity along with a reduction in glutathione. Marked impairment of memory and motor coordination was also noted. iPoCo consisting of 3 episodes of 10 s carotid artery occlusion and reperfusion instituted immediately after BCAO significantly decreased infarct size, memory impairment, motor incoordination, and altered biochemistry. Pretreatment with tadalafil mimicked the neuroprotective effects of iPoCo. The tadalafil-induced neuroprotective effects were significantly attenuated by l-NAME, a nonselective NOS inhibitor. We concluded that tadalafil mimics the neuroprotective effects of iPoCo, probably through a nitric oxide dependent pathway, and PDE-5 could be a target of interest with respect to the neuroprotective mechanism of iPoCo.

Preconditioning provides neuroprotection in models of CNS disease: paradigms and clinical significance

Preconditioning is a phenomenon in which brief episodes of a sublethal insult induce robust protection against subsequent lethal injuries. Preconditioning has been observed in multiple organisms and can occur in the brain as well as other tissues. Extensive animal studies suggest that the brain can be preconditioned to resist acute injuries, such as ischemic stroke, neonatal hypoxia/ischemia, surgical brain injury, trauma, and agents that are used in models of neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Effective preconditioning stimuli are numerous and diverse, ranging from transient ischemia, hypoxia, hyperbaric oxygen, hypothermia and hyperthermia, to exposure to neurotoxins and pharmacological agents. The phenomenon of "cross-tolerance," in which a sublethal stress protects against a different type of injury, suggests that different preconditioning stimuli may confer protection against a wide range of injuries. Research conducted over the past few decades indicates that brain preconditioning is complex, involving multiple effectors such as metabolic inhibition, activation of extra- and intracellular defense mechanisms, a shift in the neuronal excitatory/inhibitory balance, and reduction in inflammatory sequelae. An improved understanding of brain preconditioning should help us identify innovative therapeutic strategies that prevent or at least reduce neuronal damage in susceptible patients. In this review, we focus on the experimental evidence of preconditioning in the brain and systematically survey the models used to develop paradigms for neuroprotection, and then discuss the clinical potential of brain preconditioning.

Neuroprotective effect of tadalafil, a PDE-5 inhibitor, and its modulation by L-NAME in mouse model of ischemia-reperfusion injury

BACKGROUND

The present study investigates the neuroprotective effect of tadalafil, a selective phosphodiesterase-5 inhibitor, in a mouse model of ischemia-reperfusion injury.

MATERIALS AND METHODS

Bilateral carotid artery occlusion for 12 min followed by reperfusion for 24 h was employed to produce ischemia-reperfusion-induced cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test. Degree of motor incoordination was evaluated using inclined beam walk test, rota-rod test, and lateral push test. Brain nitrite/nitrate, brain acetylcholinesterase activity, brain thiobarbituric acid reactive species, and glutathione levels were also estimated.

RESULTS

Bilateral carotid artery occlusion, followed by reperfusion, produced a significant rise in cerebral infarct size, brain nitrite/nitrate levels, acetylcholinesterase activity, and thiobarbituric acid reactive species level along with a fall in glutathione. A significant impairment of memory and motor coordination was also noted. Pretreatment of tadalafil significantly attenuated the above effects of ischemia-reperfusion injury. Tadalafil-induced neuroprotective effects were significantly attenuated by administration of L-NAME, a nonselective nitric oxide synthase inhibitor.

CONCLUSIONS

Results indicate that tadalafil exerts neuroprotective effects, probably through nitric oxide-dependent pathways. Therefore, phosphodiesterase-5 can be explored as an important target to contain ischemia-reperfusion injury.

Neuroprotective effect of gadolinium: a stretch-activated calcium channel blocker in mouse model of ischemia-reperfusion injury

The present study was designed to investigate the potential of gadolinium, a stretch-activated calcium channel blocker in ischemic reperfusion (I/R)-induced brain injury in mice. Bilateral carotid artery occlusion of 12 min followed by reperfusion for 24 h was given to induce cerebral injury in male Swiss mice. Cerebral infarct size was measured using triphenyltetrazolium chloride staining. Memory was assessed using Morris water maze test and motor incoordination was evaluated using rota-rod, lateral push, and inclined beam walking tests. In addition, total calcium, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), and acetylcholinesterase (AChE) activity were also estimated in brain tissue. I/R injury produced a significant increase in cerebral infarct size. A significant loss of memory along with impairment of motor performance was also noted. Furthermore, I/R injury also produced a significant increase in levels of TBARS, total calcium, AChE activity, and a decrease in GSH levels. Pretreatment of gadolinium significantly attenuated I/R-induced infarct size, behavioral and biochemical changes. On the basis of the present findings, we can suggest that opening of stretch-activated calcium channel may play a critical role in ischemic reperfusion-induced brain injury and that gadolinium has neuroprotective potential in I/R-induced injury.