A novel therapeutic application of solid lipid nanoparticles encapsulated thymoquinone (TQ-SLNs) on 3-nitroproponic acid induced Huntington’s disease-like symptoms in wistar rats
Introduction
Huntington’s disease (HD) is an incurable, progressive neurodegenerative disease characterized by chorea, seizures, involuntary movements, dystonia, cognitive decline and emotional disturbances [1]. The hallmark of HD pathogenesis includes excitotoxic events, oxidative stress, impaired energy metabolism, mitochondrial dysfunction, altered synaptic transmission and transcriptional dysregulation [2]. The mechanistic background of HD remains unclear, nevertheless mutant htt protein (huntingtin protein with poly CAG repeats) largely aggregate in the caudate nucleus and putamen of basal ganglia and causes degeneration [3], [4].
Experimentally HD can be mimicked by an environmental mycotoxin 3-nitropropionic acid (3-NP) that efficiently replicates both the neurobehavioral alterations and striatal lesions [5]. 3-NP irreversibly inhibits succinate dehydrogenase (SDH) enzyme located in the inner domain of mitochondrial membrane, hence alters the mitochondrial electron transport chain and Krebs cycle, which leads to electron leakage from the mitochondria, bioenergetics failure and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) [6]. In addition, systemic application of 3-NP evoked a selective striatal loss closely resembling lesions that observed in the course of Huntington’s disease [5], [7].
Nigella sativa L., commonly known as black seed or black cumin, has been used in folk medicine as a natural remedy for the conditions such as respiratory illness, stomach and intestinal problems, kidney and liver functions, circulatory and immune system support, and for general well-being [8]. Most of the biological activity of the seeds has been shown to be due to thymoquinone (TQ) (2-isopropyl-5-methyl-1,2-benzoquinone), the major component of volatile oil [9]. Interestingly, this pharmacologically active lipophilic quinone is greatly responsible for many of the seed antioxidant and anti-inflammatory effects [10], hence it is frequently used in herbal medicine for treating various ailments. Furthermore, it has numerous beneficial properties including anti-inflammatory actions [11], neuroprotection [12] and suppression of oxidative stress-induced neuropathy [13]. TQ also improves neuronal morphology and reduces its degeneration during chronic toluene exposure [14], further it shows significant anti-anxiety like activity by modulating the levels of nitric oxide (NO) and γ-amino butyric acid (GABA) [15], and reduces nuclear factor kappa B (NF-KB) activation in brain and spinal cord [16].
Despite of various therapeutic efficacy of TQ, this compound suffers from poor solubility and high hydrophobicity leading to poor formulations for pharmaceutical applications [17]. This problem was solved by nanoparticulate encapsulation system. Solid lipid nanoparticles are emphasized to be a suitable colloidal carrier for the delivery of hydrophobic drugs to the central nervous systems (CNS) [18]. Considerably, SLNs were found to promote the stability, absorption and pharmacokinetic properties of the drug. In addition, it also improves drug payload, sustained drug release ability and drug targeting potential [19], [20]. Earlier we have formulated and characterized thymoquinone encapsulated solid lipid nanoparticles (TQ-SLNs) [21], further the developed formulations were found to be spherical shaped structure with the particle size of 172.10 ± 7.41 nm and maximum drug entrapment of 84.49 ± 3.36%. Also, drug release potential of 86.15 ± 2.76% for 72 h has been derived. Consequently, Singh et al. [22]reported that there was 5-fold increase in bio-availability of TQ when incorporated into SLNs. Hence, further studies have been attempted for the first time to evaluate the pharmacodynamic efficacy of developed solid lipid nanoparticles encapsulated thymoquinone (TQ-SLNs) in comparison with thymoquinone suspension (TQ-S) in alleviating 3-NP induced body weight change, behavioral impairments, oxidative cell damage and striatal cell pathology.
Section snippets
Chemicals and reagents
3-Nitropropionic acid and Thymoquinone were purchased from Sigma Chemical Co. (St. Louis, USA). Stearic acid, Soy Lecithin and Sodium taurocholate were purchased from Himedia Laboratories Pvt. Ltd. (Mumbai, India). Glutathione reduced form (GSH), glutathione oxidized form (GSSG), 1-chloro-2, 4-dinitrobenzene (CDNB), 5,5′-dithiobis-2-nitrobenzoic acid (DTNB) were purchased from Sisco Research Laboratories Pvt. Ltd. (Mumbai, India). β- Nicotinamide adenine dinucleotide phosphate reduced (NADPH)
Effect of TQ-SLNs and TQ-S on body weight mass in 3-NP induced rats
Intraperitoneal administration of 3-NP (10 mg/kg) resulted ina significant (P < 0.01) decline in the body weight of the animals as compared to vehicle treated group. Simultaneously, treatment with TQ-SLNs (10and 20 mg/kg) and TQ suspension (80 mg/kg)significantly (P < 0.01) attenuate the loss in body weight caused by 3-NP. Moreover, TQ-S at 40 mg/kg treatment also showed a significant (P < 0.05) rise in body weight measurement. Subsequently, treatment with TQ-SLNs alone and blank SLNs did not
Discussion and conclusion
Systemic administration of 3-NP has been suggested to impair energy metabolism, ROS generation and finally causes apoptosis, therefore it is considered to be a reliable tool in mimicking HD in animal models [49]. Recently, nanoparticulate system has been raised to improve the therapeutic strategy for brain oriented degenerative diseases like HD. Solid lipid nanoparticles (SLNs) physicochemical characteristics are particularly regarded to address the critical issues related to the brain
Conflicts of interest
The authors declare that no conflicts of interest exist.
Acknowledgement
The first author is grateful to UGC for the financial support in the form of JRF – UGC – Non Net Fellowship (Co/Tara/UGC-Non-Net/UGC-XII Plan/Medical Bio/2014/703 dated 28th March 2014).
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