Allicin Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection In Vitro and Alleviates Inflammatory Responses

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically important pathogens to the swine industry worldwide over the past three decades. No approved effective antiviral drug is available to control this virus. The antiviral effects of allicin (diallyl thiosulfinate) on many human and animal viruses have been documented. However, the antiviral effect of allicin on PRRSV infection remains unknown. In this study, we found that allicin exhibited an inhibitory effect on HP-PRRSV and NADC30-like PRRSV in a dose-dependent manner by interfering with viral entry, replication, and assembly. Furthermore, allicin alleviated the expression of pro-inflammatory cytokines (IFN-β, IL-6, and TNFα) induced by PRRSV infection. The pro-inflammatory signaling pathways, TNF signaling pathway and MAPK signaling pathway, up-regulated by PRRSV infection were restored by allicin treatment. Taken together, these results demonstrate that allicin has antiviral activity against PRRSV and ameliorates inflammatory responses induced by PRRSV infection, suggesting that allicin is a promising drug candidate for anti-PRRSV therapy in vivo.

Potential diagnostic biomarkers for lead-induced hepatotoxicity and the role of synthetic chelators and bioactive compounds

Lead (Pb2+) poisoning is a public health concern of global dimensions. Although several public health guidelines and workplace safety policies are existing and enforced, lead toxicity cases are drastically increasing. Lead exposure leads to numerous harmful consequences and causes adverse effects on different body organs and systems, mainly via the generation of reactive oxygen species, leading to augmented oxidative stress, competing with metal ions, and binding with the sulfhydryl groups. In several instances, lead poisoning cases remain undiagnosed and untreated or receive only symptomatic treatment. Estimation of blood lead levels reflects only a recent exposure, however, which does not reveal the total body burden. This review summarizes the effects of lead with special reference to hepatotoxicity and some of the potential diagnostic biomarkers. Furthermore, it also focuses on synthetic chelators used in the treatment of lead poisoning and the advantage of using bioactive compounds with an emphasis on the ameliorative effect of garlic.

Allicin ameliorates imiquimod-induced psoriasis-like skin inflammation via disturbing the interaction of keratinocytes with IL-17A

BACKGROUND AND PURPOSE

Psoriasis is an inflammatory skin disease of chronic recurrence mediated by the interaction between IL-17 and keratinocytes, which sustains a vicious circle of inflammation. Safe and effective natural medicine is a potential strategy for the clinical treatment of psoriasis. Given its prominent anti-proliferative and anti-inflammatory properties, we investigated the actions of allicin in improving psoriasis.

EXPERIMENTAL APPROACH

Pharmacodynamic studies were carried out in mice after topical administration of allicin against psoriasis-like lesions induced by imiquimod. Skin sensitization tests were evaluated on guinea pigs. Toxicological studies and skin irritation tests were assessed by consecutive topical allicin alone on the skin of rabbits. RNA-seq probed transcriptomic changes following allicin. Western blot explored the actions of allicin on the interaction between IL-17A and keratinocytes. Changes in inflammatory factor expression were analysed by qPCR and immunohistochemistry.

KEY RESULTS

Allicin significantly improved the epidermal structure by inhibiting the excessive proliferation and reduced apoptosis of keratinocytes. Furthermore, allicin reduced the secretion of inflammatory cytokines (IL-17A/F, IL-22, IL-12, and IL-20), chemokines (CXCL2, CXCL5, and CCL20), and anti-bacterial peptides (S100a8/9). Mechanistically, allicin directly inhibited the IL-17-induced TRAF6/MAPK/NF-κB and STAT3/NF-κB signalling cascades in keratinocytes, thus breaking the positive inflammatory feedback and alleviating imiquimod-induced psoriasis-like dermatitis in mice. Importantly, topical administration of allicin did not cause skin allergy, and the safety and adaptability of long-term application were verified.

CONCLUSIONS AND IMPLICATIONS

Interfering with IL-17 signalling in keratinocytes with allicin is a promising strategy for treating psoriasis, given its safety and effectiveness.

A review on garlic as a supplement for Alzheimer's disease: a mechanistic insight in its direct and indirect effects

Alzheimer's disease (AD) is one of the most complicated neurodegenerative diseases causing dementia in human beings. Aside from that incidence of AD is increasing also its treatment is very complicated. There are several known hypotheses regarding the pathology of Alzheimer's disease, including the Amyloid beta hypothesis, Tau hypothesis, inflammation hypothesis, and cholinergic hypothesis, which are investigated in different researches to completely elucidate the pathology of AD. Aside from these some new mechanisms such as immune, endocrine, and vagus pathways, as well as bacteria metabolite secretions are being explained as other causes that are somehow related to AD pathogenesis. There is still no definite treatment for Alzheimer's disease that can completely cure and eradicate AD. Garlic (Allium sativum) is a traditional herb used as a spice in different cultures and due to the organosulfur compounds like allicin it possesses highly anti-oxidant properties and the benefits of garlic in cardiovascular diseases like hypertension and atherosclerosis is examined and reviewed, although its beneficiary effects in neurodegenerative diseases such as AD is not completely understood. In this review, we discuss the effects of garlic based on its components such as allicin, S-allyl cysteine on Alzheimer's disease and the mechanisms that garlic components can be beneficiary for AD patients, including its effects amyloid beta, oxidative stress, tau protein, gene expression, and cholinesterase enzymes. Based on the literature review we have done, garlic has revealed beneficiary effects on Alzheimer's disease, especially in animal studies; however, more studies should be done on human populations to find the exact mechanism of garlic effects on AD patients.

Medicinal and therapeutic properties of garlic, garlic essential oil, and garlic-based snack food: An updated review

Garlic (Allium sativum) is an edible tuber belonging to the family Liliaceae. It has been used since ancient times as a spice to enhance the sensory characteristics of food and as a household remedy for the treatment of a variety of ailments. Garlic has been studied for its medicinal and therapeutic effects in the treatment of various human diseases for a long time. Health benefits associated with the consumption of garlic are attributed to the various sulfur compounds present in it such as allicin, ajoene, vinyl-dithiin, and other volatile organosulfur compounds which are all metabolized from alliin. Several researches in the literature have shown evidence that garlic exhibits antioxidant, antiviral, anti-microbial, anti-fungal, antihypertensive, anti-anemic, anti-hyperlipidemic, anticarcinogenic, antiaggregant, and immunomodulatory properties. The present review identifies and discusses the various health benefits associated with the consumption of garlic, its essential oil, and bioactive constituents, along with exploring the various snack-food products developed by incorporating garlic.

Synergistic Antibacterial Effect and Mechanism of Allicin and an Enterobacter cloacae Bacteriophage

Enterobacter cloacae is a troublesome pathogen causing refractory infections of the lower respiratory tract, urethra and abdominal cavity, endocarditis, osteomyelitis, and neonatal septicemia. It is prone to developing resistance to ordinary antibiotics and has brought a serious problem to clinical treatment. An artful synergistic combination of an antibacterial natural product allicin and a newly isolated bacteriophage, named BD523, was constructed herein. This combination significantly lowered effective dosage of allicin and effectually overcame bacterial drug-resistance. We experimentally evidenced that allicin interacts with bacterial DNA in the groove region by inserting itself into the DNA double helix and, subsequently, disrupts the bacterial DNA by cleaving phosphate diester bonds of deoxynucleotides. Further, BD523 destroys the cell wall and membrane of bacteria by synthesizing lyase proteins, including holin and endolysins. Thus, the synergistic effect of the combination benefits from complementary targeting mechanisms of allicin and BD523. They cooperatively act on bacterial DNA, cell wall, and membrane to improve antibacterial efficiency and avoid drug-resistance. IMPORTANCE Bacterial drug-resistance is a serious problem afflicting pharmacologists all over the world. Many strategies have been developed and practiced to overcome it, but almost no one is satisfactory due to the continual change of bacteria. Combinations of antibiotics and bacteriophages are promising because of the cooperation of 2 bacterial killers with distinct mechanisms. The combination of allicin and an Enterobacter cloacae bacteriophage reported herein can significantly improve the effect of allicin against E. cloacae. Its synergistic effect was even superior to the combination of bacteriophage and neomycin, of which the MIC was significantly lower than allicin. It was ascribed to the complementary antibacterial and the possible resistance-proof mechanism of bacteriophage and allicin. This study provided a pragmatic way to conquer the cunning bacterium, and may offer reference for research and development of new bacterial killers.

Allicin Alleviated LPS-Induced Mastitis via the TLR4/NF-κB Signaling Pathway in Bovine Mammary Epithelial Cells

Dairy farming is the most important economic activity in animal husbandry. Mastitis is the most common disease in dairy cattle and has a significant impact on milk quality and yield. The natural extract allicin, which is the main active ingredient of the sulfur-containing organic compounds in garlic, has anti-inflammatory, anticancer, antioxidant, and antibacterial properties; however, the specific mechanism underlying its effect on mastitis in dairy cows needs to be determined. Therefore, in this study, whether allicin can reduce lipopolysaccharide (LPS)-induced inflammation in the mammary epithelium of dairy cows was investigated. A cellular model of mammary inflammation was established by pretreating bovine mammary epithelial cells (MAC-T) with 10 µg/mL LPS, and the cultures were then treated with varying concentrations of allicin (0, 1, 2.5, 5, and 7.5 µM) added to the culture medium. MAC-T cells were examined using RT-qPCR and Western blotting to determine the effect of allicin. Subsequently, the level of phosphorylated nuclear factor kappa-B (NF-κB) was measured to further explore the mechanism underlying the effect of allicin on bovine mammary epithelial cell inflammation. Treatment with 2.5 µM allicin considerably decreased the LPS-induced increase in the levels of the inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) and inhibited activation of the NOD-like receptor protein 3 (NLRP3) inflammasome in cow mammary epithelial cells. Further research revealed that allicin also inhibited the phosphorylation of inhibitors of nuclear factor kappa-B-α (IκB-α) and NF-κB p65. In mice, LPS-induced mastitis was also ameliorated by allicin. Therefore, we hypothesize that allicin alleviated LPS-induced inflammation in the mammary epithelial cells of cows probably by affecting the TLR4/NF-κB signaling pathway. Allicin will likely become an alternative to antibiotics for the treatment of mastitis in cows.

The protective roles of allicin on type 1 diabetes mellitus through AMPK/mTOR mediated autophagy pathway

Background: Type 1 diabetes mellitus (T1DM) is one of the most common endocrine and metabolic diseases in children. Pancreatic β cells are thought to be critical cells involved in the progression of T1DM, and their injury would directly lead to impaired insulin secretion. Purpose: To investigate the protective effects of allicin on pancreatic β cell injury and elucidate the underlying mechanism. Methods: The streptozotocin (STZ)-induced mouse T1DM model in vivo and STZ-induced pancreatic β cell Min6 model in vitro were used to explore the effects of allicin on T1DM. The experiments include fasting blood glucose test, oral glucose tolerance detection, HE staining, immunohistochemistry, immunofluorescence, TUNEL staining, western blot, real-time quantitative PCR (RT-qPCR), and flow cytometry. Results: Allicin could significantly decrease blood glucose level, improve islet structure and insulin expression, and inhibit apoptosis to reduce STZ-induced pancreatic β cell injury and loss through activating AMPK/mTOR mediated autophagy pathway. Conclusion: Allicin treatment significantly reduced STZ-induced T1DM progression, suggesting that allicin may be a potential therapy option for T1DM patients.

Natural Compound Allicin Containing Thiosulfinate Moieties as Transmembrane Protein 16A (TMEM16A) Ion Channel Inhibitor for Food Adjuvant Therapy of Lung Cancer

Cancer is one of the most serious malignant diseases, and chemotherapy is cancer's main clinical treatment method. However, chemotherapy inevitably produces drug resistance, and side effects accompany them. Adjuvant therapy is an effective way to enhance chemotherapeutic drug sensitivity and reduce side effects. This study found allicin, garlic's active ingredient, is an inhibitor of transmembrane protein 16A (TMEM16A), a novel drug target of lung adenocarcinoma. Allicin concentration-dependently inhibited TMEM16A currents with an IC₅₀ of 24.35 ± 4.14 μM. Allicin thiosulfinate moieties bound with R535A/E624A/E633A residues of TMEM16A blocked the ion transport function and downregulated TMEM16A protein expression affecting the mitogen-activated protein kinase signal transduction. Then, allicin reduced the viability and migration of LA795 cells, and induced cell apoptosis. Moreover, multitarget combination administration results indicated that the therapeutic effect of 3.56 mg/kg allicin and 3 mg/kg cisplatin combined administration was superior to the superposition of the two drugs alone, demonstrating that the anticancer effects of allicin and cisplatin were synergistic. In addition, low-concentration combined administration also avoided the side effects of cisplatin in mice. Based on the good tumor suppressor effect and high biosafety of allicin and cisplatin combination in vivo, allicin can be used for food adjuvant therapy of cisplatin chemotherapy.

Garlic (Allium sativum L.) as an Ally in the Treatment of Inflammatory Bowel Diseases

For centuries, garlic (Allium sativum) has been used both as a traditional remedy for most health-related ailments and for culinary purposes. Current preclinical investigations have suggested that dietary garlic intake has beneficial health effects, such as antioxidant, anti-inflammatory, antitumor, antiobesity, antidiabetic, antiallergic, cardioprotective, and hepatoprotective effects. Its therapeutic potential is influenced by the methods of use, preparation, and extraction. Of particular importance is the Aged Garlic Extract (AGE). During the aging process, the odorous, sour, and irritating compounds in fresh raw garlic, such as allicin, are naturally converted into stable and safe compounds that have significantly greater therapeutic effects than fresh garlic. In AGE, S-allylcysteine (SAC) and S-allylmercaptocysteine (SAMC) are the major water-soluble organosulfurized compounds (OSCs). SAC has been extensively studied, demonstrating remarkable antioxidant, anti-inflammatory, and immunomodulatory capacities. Recently, AGE has been suggested as a promising candidate for the maintenance of immune system homeostasis through modulation of cytokine secretion, promotion of phagocytosis, and activation of macrophages. Since immune dysfunction plays an important role in the development and progress of various diseases, given the therapeutic effects of AGE, it can be thought of exploiting its immunoregulatory capacity to contribute to the treatment and prevention of chronic inflammatory bowel diseases (IBD).

Isolation of Garlic Bioactives by Pressurized Liquid and Subcritical Water Extraction

Garlic (Allium sativum L.) is widely used in various food products and traditional medicine. Besides unique taste and flavour, it is well known for its chemical profile and bioactive potential. The aim of this study was to apply subcritical water extraction (SWE) and pressurized liquid extraction (PLE) for the extraction of bioactive compounds from the Ranco genotype of garlic. Moreover, PLE process was optimized using response surface methodology (RSM) in order to determine effects and optimize ethanol concentration (45-75%), number of cycles (1-3), extraction time (1-3 min) and temperature (70-110 °C) for maximized total phenols content (TP) and antioxidant activity evaluated by various in vitro assays. Furthermore, temperature effect in SWE process on all responses was evaluated, while allicin content (AC), as a major organosulphur compound, was determined in all samples. Results indicated that PLE provided tremendous advantage over SWE in terms of improved yield and antioxidant activity of garlic extracts. Therefore, high-pressure processes could be used as clean and green procedures for the isolation of garlic bioactives.

Effects of allicin on human Simpson-Golabi-Behmel syndrome cells in mediating browning phenotype

INTRODUCTION

Obesity is a major health problem because it is associated with increased risk of cardiovascular disease, diabetes, hypertension, and some cancers. Strategies to prevent or reduce obesity focus mainly on the possible effects of natural compounds that can induce a phenotype of browning adipocytes capable of releasing energy in the form of heat. Allicin, a bioactive component of garlic with numerous pharmacological functions, is known to stimulate energy metabolism.

METHODS

In the present study, the effects of allicin on human Simpson-Golabi-Behmel Syndrome (SGBS) cells were investigated by quantifying the dynamics of lipid droplets (LDs) and mitochondria, as well as transcriptomic changes after six days of differentiation.

RESULTS

Allicin significantly promoted the reduction in the surface area and size of LDs, leading to the formation of multilocular adipocytes, which was confirmed by the upregulation of genes related to lipolysis. The increase in the number and decrease in the mean aspect ratio of mitochondria in allicin-treated cells indicate a shift in mitochondrial dynamics toward fission. The structural results are confirmed by transcriptomic analysis showing a significant arrangement of gene expression associated with beige adipocytes, in particular increased expression of T-box transcription factor 1 (TBX1), uncoupling protein 1 (UCP1), PPARG coactivator 1 alpha (PPARGC1A), peroxisome proliferator-activated receptor alpha (PPARA), and OXPHOS-related genes. The most promising targets are nuclear genes such as retinoid X receptor alpha (RXRA), retinoid X receptor gamma (RXRG), nuclear receptor subfamily 1 group H member 3 (NR1H3), nuclear receptor subfamily 1 group H member 4 (NR1H4), PPARA, and oestrogen receptor 1 (ESR1).

DISCUSSION

Transcriptomic data and the network pharmacology-based approach revealed that genes and potential targets of allicin are involved in ligand-activated transcription factor activity, intracellular receptor signalling, regulation of cold-induced thermogenesis, and positive regulation of lipid metabolism. The present study highlights the potential role of allicin in triggering browning in human SGBS cells by affecting the LD dynamics, mitochondrial morphology, and expression of brown marker genes. Understanding the potential targets through which allicin promotes this effect may reveal the underlying signalling pathways and support these findings.

Garlic (Allium sativum L.) in diabetes and its complications: Recent advances in mechanisms of action

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia and impaired islet secretion that places a heavy burden on the global health care system due to its high incidence rate, long disease course and many complications. Fortunately, garlic (Allium sativum L.), a well-known medicinal plant and functional food without the toxicity and side effects of conventional drugs, has shown positive effects in the treatment of diabetes and its complications. With interdisciplinary development and in-depth exploration, we offer a clear and comprehensive summary of the research from the past ten years, focusing on the mechanisms and development processes of garlic in the treatment of diabetes and its complications, aiming to provide a new perspective for the treatment of diabetes and promote the efficient development of this field.

Allicin Alleviates Diabetes Mellitus by Inhibiting the Formation of Advanced Glycation End Products

Advanced glycation end products (AGEs) cause damage to pancreatic β-cells and trigger oxidative stress and inflammation, which promotes the development and progression of diabetes and its complications. Therefore, it is important to inhibit the formation of AGEs as part of the treatment of diabetes. Allicin is a natural antimicrobial agent with abundant pharmacological activities, and recent studies have reported its therapeutic effects in diabetes; however, the mechanism of these therapeutic effects is still unclear. Thus, the purpose of this study was to further investigate the association between allicin treatment of diabetes and AGEs. First, we established a streptozocin (STZ)-induced diabetic rat model and treated the rats with allicin for six weeks. We measured glycolipid metabolism, AGE levels, receptor of advanced glycation end products (RAGE) levels, oxidative stress, and other related indicators. The results showed that allicin improved blood glucose and body weight, reduced lipid accumulation, and inhibited AGE formation in rats. Treatment with allicin also inhibited RAGEs and thereby prevented AGE activity, which, in turn, alleviated oxidative stress and promoted insulin secretion. To further verify the effect of allicin on AGEs, we also performed in vitro nonenzymatic glycation simulation experiments. These results showed that allicin inhibited the production of AGEs by suppressing the production of AGEs intermediates. Thus, our research suggests that allicin may alleviate diabetes by inhibiting the formation of AGEs and reducing RAGE levels to relieve oxidative stress and promote insulin secretion.

Black Garlic and Thiosulfinate-Enriched Extracts as Adjuvants to Ceftriaxone Treatment in a Rat Peritonitis Model of Sepsis

To date, there have been no new drugs or adjuvants able to decrease both morbidity and mortality in the context of sepsis and septic shock. Our objective was to evaluate the use of thiosulfinate-enriched Allium sativum and black garlic extracts as adjuvants in the management of sepsis. An experimental in vivo study was carried out with male Sprague-Dawley^® rats. Animals were randomized in four treatment groups: antibiotic (ceftriaxone) treatment (group I), ceftriaxone plus thiosulfinate-enriched extract (TASE, group II), ceftriaxone plus thiosulfinate-enriched extract and black garlic extracts (TASE + BGE, group III), and ceftriaxone plus black garlic extract (BGE, group IV). All animals were housed and inoculated with 1 × 10¹⁰ CFU/15 mL of intraperitoneal Escherichia coli ATCC 25922. Subsequently, they received a daily treatment according to each group for 7 days. Clinical, analytical, microbiological, and histopathological parameters were evaluated. Statistically significant clinical improvement was observed in rats receiving garlic extracts in weight (groups II and III), ocular secretions, and piloerection (group IV). Moreover, less liver edema, vacuolization, and inflammation were observed in groups receiving adjuvant support (groups II, III, and IV). When comparing interleukins 24 h after bacteria inoculum, we found statistically significant differences in TNF-alpha levels in groups receiving BGE (groups III and IV, p ≤ 0.05). Blood and peritoneal liquid cultures were also analyzed, and we detected a certain level of Enterococcus faecalis in peritoneal cultures from all treatment groups and less bacteria presence in blood cultures in rats receiving garlic extracts (groups II, III, and IV). In conclusion, TASE and BGE could be promising nutraceutical or medicinal agents as coadjuvants in the treatment of sepsis because of its effects in modulating the inflammatory response.

Allicin and Capsaicin Ameliorated Hypercholesterolemia by Upregulating LDLR and Downregulating PCSK9 Expression in HepG2 Cells

Hypercholesterolemia is a common cause of cardiovascular diseases (CVDs). Although allicin and capsaicin possess hypolipidemic effects through several molecular mechanisms, their effects on LDLR and PCSK9 expression are still unknown. This study aimed to investigate the effects of allicin and capsaicin on LDLR and PCSK9 expression in HepG2 cells. The effects of allicin and capsaicin on cell viability were evaluated by MTT assay and trypan blue exclusion assay. Low-density lipoprotein receptor (LDLR) levels and LDL uptake were determined by flow cytometry and confocal laser scanning microscopy (CLSM), respectively. RT-qPCR and Western blot analyses were performed to evaluate the expression of PCSK9, LDLR, SREBP-2, and HNF1α. ELISA was used to measure PCSK9 levels in culture media. Allicin and capsaicin increased the protein expression levels of LDLR via activation of the transcription factor SREBP2. However, allicin and capsaicin decreased the expression of PCSK9 protein and the secretion of PCSK9 in culture media via the suppression of HNF1α. Moreover, allicin and capsaicin increased LDL uptake into HepG2 cells. The efficacies of the hypolipidemic effects of allicin (200 µM) and capsaicin (200 µM) were comparable to that of atorvastatin (10 µM) in this study. In conclusion, allicin and capsaicin possessed hypolipidemic effects via the upregulation of LDLR and downregulation of PCSK9 expression, thereby enhancing LDL uptake into HepG2 cells. This indicates that allicin and capsaicin should be used as potent supplements to ameliorate hypercholesterolemia.

Allicin shows antifungal efficacy against Cryptococcus neoformans by blocking the fungal cell membrane

Allicin, which is generated by the catalytic reaction between alliin and alliinase extracted from garlic, has been shown to have a wide range of antimicrobial activities, but its anti-Cryptococcus efficacy and mechanism are not quite clear. Here, we have determined that the Conversion rate of allicin in the reaction product reached 97.5%. The minimal inhibitory concentration (MIC) of allicin against Cryptococcus neoformans (C. neoformans) H99 was 2 μg/ml, which is comparable to fluconazole (FLU, 1 μg/ml). Furthermore, allicin exhibited effective antifungal activity against 46 clinical isolates of C. neoformans, and the MICs ranged from 1 to 8 μg/ml, even for AmB-insensitive strains. Interestingly, allicin also exerted additive or synergistic effects when combined with amphotericin B (AmB) and FLU. Time-killing curves and long-term live cell imaging of H99 showed that 4 MIC of allicin had fungicide activity. Additionally, allicin (4 and 8 mg/kg) exerted a dose-dependent therapeutic effect on H99-infected mice by significantly reducing the wet pulmonary coefficient and Cryptococcus load and reducing lung damage. Even the efficacy of 8 mg/kg was comparable to FLU (20 mg/kg). Transcriptomics revealed that allicin may act on the cell membrane of H99. Subsequently, transmission electron microscopy (TEM) observations showed that allicin clearly breached the cell membrane and organelles of H99. Confocal laser scanning microscopy (CLSM) results further confirmed that allicin disrupted the permeability of the cell membranes of H99 in a dose-dependent manner. Allicin exhibits strong anti-C. neoformans activity in vitro and in vivo, mainly by destroying the permeability and related functions of Cryptococcus cell membranes.

AGR2-induced cholesterol synthesis drives lovastatin resistance that is overcome by combination therapy with allicin

Anterior gradient 2 (AGR2), a protein disulfide isomerase (PDI), is a multifunctional protein under physiological and pathological conditions. In this study we investigated the roles of AGR2 in regulating cholesterol biogenesis, lipid-lowering efficiency of lovastatin as well as in protection against hypercholesterolemia/statin-induced liver injury. We showed that AGR2 knockout significantly decreased hepatic and serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in mice with whole-body or hepatocyte-specific Agr2-null mutant, compared with the levels in their wild-type littermates fed a normal chow diet (NCD) or high-fat diet (HFD). In contrast, mice with AGR2 overexpression (Agr2/Tg) exhibited an increased cholesterol level. Mechanistic studies revealed that AGR2 affected cholesterol biogenesis via activation of AKT/sterol regulatory element-binding protein-2 (SREBP2), to some extent, in a PDI motif-dependent manner. Moreover, elevated AGR2 led to a significant decrease in the lipid-lowering efficacy of lovastatin (10 mg· kg-1· d-1, ip, for 2 weeks) in mice with hypercholesterolemia (hyperCho), which was validated by results obtained from clinical samples in statin-treated patients. We showed that lovastatin had limited effect on AGR2 expression, but AGR2 was inducible in Agr2/Tg mice fed a HFD. Further investigations demonstrated that drug-induced liver toxicity and inflammatory reactions were alleviated in hypercholesterolemic Agr2/Tg mice, suggesting the dual functions of AGR2 in lipid management and hyperCho/statin-induced liver injury. Importantly, the AGR2-reduced lipid-lowering efficacy of lovastatin was attenuated, at least partially, by co-administration of a sulfhydryl-reactive compound allicin (20 mg· kg-1· d-1, ip, for 2 weeks). These results demonstrate a novel role of AGR2 in cholesterol metabolism, drug resistance and liver protection, suggesting AGR2 as a potential predictor for selection of lipid-lowering drugs in clinic.

Allicin-Inspired Heterocyclic Disulfides as Novel Antimicrobial Agents

In this work, a series of derivatives with disulfide bonds containing pyridine, pyrimidine, thiophene, thiazole, benzothiazole, and quinoline were designed and synthesized based on the various biological activities of allicin disulfide bond functional groups. The antimicrobial activities of the target compounds were determined, and the structure-activity relationships were discussed. Among them, compound S8 demonstrated the most potent antifungal activity in vitro against Monilinia fructicola (M. fructicola), with an EC₅₀ value of 5.92 μg/mL. Furthermore, an in vivo bioassay revealed that compound S8 exhibited equivalent curative and higher protective effects as the positive drug thiophanate methyl at a concentration of 200 μg/mL. The preliminary mechanism experiments showed that compound S8 could inhibit the growth of M. fructicola' s hyphae in a time- and concentration-dependent manner, and compound S8 could induce the shrinkage of hyphae, disrupt the integrity of the plasma membrane, and cause the damage and leakage of cell contents. More than that, compound S5 also demonstrated an excellent antibacterial effect on Xanthomonas oryzae (X. oryzae), with a MIC₉₀ value of 1.56 μg/mL, which was superior to the positive control, thiodiazole copper.

Cellular Mechanisms Underlying the Cardioprotective Role of Allicin on Cardiovascular Diseases

Cardiovascular diseases (CVDs) are a group of diseases in which the common denominator is the affection of blood vessels, heart tissue, and heart rhythm. The genesis of CVD is complex and multifactorial; therefore, approaches are often based on multidisciplinary management and more than one drug is used to achieve the optimal control of risk factors (dyslipidemia, hypertension, hypertrophy, oxidative stress, endothelial dysfunction, inflammation). In this context, allicin, a sulfur compound naturally derived from garlic, has shown beneficial effects on several cardiovascular risk factors through the modulation of cellular mechanisms and signaling pathways. Effective pharmacological treatments for CVD or its risk factors have not been developed or are unknown in clinical practice. Thus, this work aimed to review the cellular mechanisms through which allicin exerts its therapeutic effects and to show why it could be a therapeutic option for the prevention or treatment of CVD and its risk factors.

Allicin as a Volatile or Nebulisable Antimycotic for the Treatment of Pulmonary Mycoses: In Vitro Studies Using a Lung Flow Test Rig

Fungal infections of the lung are an increasing problem worldwide and the search for novel therapeutic agents is a current challenge due to emerging resistance to current antimycotics. The volatile defence substance allicin is formed naturally by freshly injured garlic plants and exhibits broad antimicrobial potency. Chemically synthesised allicin was active against selected fungi upon direct contact and via the gas phase at comparable concentrations to the pharmaceutically used antimycotic amphotericin B. We investigated the suppression of fungal growth by allicin vapour and aerosols in vitro in a test rig at air flow conditions mimicking the human lung. The effect of allicin via the gas phase was enhanced by ethanol. Our results suggest that allicin is a potential candidate for development for use in antifungal therapy for lung and upper respiratory tract infections.

Anti-inflammatory and Anti-bacterial Effects of Allicin-coated Tracheal Tube on Trachea Mucosa

BACKGROUND/AIM

Allicin has been known to improve wound healing via antimicrobial and anti-inflammatory properties. The aim of this study was to evaluate whether an allicin-coated tracheal tube can prevent tracheal stenosis through improving wound healing after tracheal injury.

MATERIALS AND METHODS

Allicin-coated silicone tracheal tube (t-tube) was prepared by the polydopamine-mediated coating method. Tracheal mucosa was injured, and an allicin-coated t-tube was placed into the trachea to evaluate mucosal changes until designated time point. Anti-inflammatory, anti-bacterial and cytotoxic effects of allicin were also investigated in in vitro.

RESULTS

Allicin- coated silicone was not cytotoxic, and it showed anti-inflammatory and anti-bacterial effects in in vitro analysis. The use of allicin-coated t-tube in a rabbit model showed favorable mucosal healing with significant decrease of proinflammatory cytokines compared to the non-coated tube group. The allicin-coated tube showed obvious decreased number of cocci-shaped bacterial attached to the tube surface. From the histological point of view, the allicin- coated tube showed faster regeneration of the normal respiratory epithelial structure compared to the non-coated group.

CONCLUSION

Allicin-coated t-tube showed anti-inflammatory and anti-bacterial effects on injured tracheal mucosa. We suggest that allicin-coated t-tube can be used for promoting physiological wound healing to prevent laryngotracheal stenosis.

Protective Effects of Allicin on Acute Myocardial Infarction in Rats via Hydrogen Sulfide-mediated Regulation of Coronary Arterial Vasomotor Function and Myocardial Calcium Transport

Acute myocardial infarction (AMI) is a condition with high morbidity and mortality, for which effective treatments are lacking. Allicin has been reported to exert therapeutic effects on AMI, but the underlying mechanisms of its action have not been fully elucidated. To investigate this, a rat model of AMI was generated by ligating the left anterior descending branch of the coronary artery. DL-propargylglycine (PAG), a specific hydrogen sulfide (H₂S) synthetase inhibitor, was used to examine the effects of allicin on H₂S production. Isolated coronary arteries and cardiomyocytes were assessed for vascular reactivity and cellular Ca²⁺ transport using a multiwire myography system and a cell-contraction-ion detection system, respectively. Allicin administration improved cardiac function and myocardial pathology, reduced myocardial enzyme levels, and increased H₂S and H₂S synthetase levels. Allicin administration resulted in concentration-dependent effects on coronary artery dilation, which were mediated by receptor-dependent Ca²⁺ channels, ATP-sensitive K⁺ channels, and sarcoplasmic reticulum (SR) Ca²⁺ release induced by the ryanodine receptor. Allicin administration improved Ca²⁺ homeostasis in cardiomyocytes by increasing cardiomyocyte contraction, Ca²⁺ transient amplitude, myofilament sensitivity, and SR Ca²⁺ content. Allicin also enhanced Ca²⁺ uptake via SR Ca²⁺-ATPase and Ca²⁺ removal via the Na⁺/Ca²⁺ exchanger, and it reduced SR Ca²⁺ leakage. Notably, the protective effects of allicin were partially attenuated by blockade of H₂S production with PAG. Our findings provide novel evidence that allicin-induced production of H₂S mediates coronary artery dilation and regulation of Ca²⁺ homeostasis in AMI. Our study presents a novel mechanistic insight into the anti-AMI effects of allicin and highlights the therapeutic potential of this compound.

Allicin, an Antioxidant and Neuroprotective Agent, Ameliorates Cognitive Impairment

Allicin (diallylthiosulfinate) is a defense molecule produced by cellular contents of garlic (Allium sativum L.). On tissue damage, the non-proteinogenic amino acid alliin (S-allylcysteine sulfoxide) is converted to allicin in an enzyme-mediated process catalysed by alliinase. Allicin is hydrophobic in nature, can efficiently cross the cellular membranes and behaves as a reactive sulfur species (RSS) inside the cells. It is physiologically active molecule with the ability to oxidise the thiol groups of glutathione and between cysteine residues in proteins. Allicin has shown anticancer, antimicrobial, antioxidant properties and also serves as an efficient therapeutic agent against cardiovascular diseases. In this context, the present review describes allicin as an antioxidant, and neuroprotective molecule that can ameliorate the cognitive abilities in case of neurodegenerative and neuropsychological disorders. As an antioxidant, allicin fights the reactive oxygen species (ROS) by downregulation of NOX (NADPH oxidizing) enzymes, it can directly interact to reduce the cellular levels of different types of ROS produced by a variety of peroxidases. Most of the neuroprotective actions of allicin are mediated via redox-dependent pathways. Allicin inhibits neuroinflammation by suppressing the ROS production, inhibition of TLR4/MyD88/NF-κB, P38 and JNK pathways. As an inhibitor of cholinesterase and (AChE) and butyrylcholinesterase (BuChE) it can be applied to manage the Alzheimer's disease, helps to maintain the balance of neurotransmitters in case of autism spectrum disorder (ASD) and attention deficit hyperactive syndrome (ADHD). In case of acute traumatic spinal cord injury (SCI) allicin protects neuron damage by regulating inflammation, apoptosis and promoting the expression levels of Nrf2 (nuclear factor erythroid 2-related factor 2). Metal induced neurodegeneration can also be attenuated and cognitive abilities of patients suffering from neurological diseases can be ameliorates by allicin administration.

In vitro Activity of Allicin Alone and in Combination With Antifungal Drugs Against Microsporum canis Isolated From Patients With Tinea Capitis

The checkerboard broth method based on the Clinical and Laboratory Standards Institute M38-A3 document was used in this study to evaluate the in vitro activity of allicin alone and in combination with the antifungal drugs (griseofulvin, fluconazole, itraconazole and terbinafine) against Microsporum canis isolated from patients with tinea capitis. When allicin was used alone, only weak anti-M. canis effects were found. The MIC₅₀, MIC₉₀ and geometric mean (GM) of terbinafine were the lowest among the compounds tested. Synergism was observed for the combinations of allicin with itraconazole and terbinafine. Only indifference was observed for the combinations of allicin with griseofulvin and fluconazole. Our study illustrated the synergism of allicin in combination with itraconazole and terbinafine, which could be a reference for the treatment of tinea capitis due to M. canis.