The pharmaco-toxicological conundrum of oleander: Potential role of gut microbiome

Floristic Account of Apocynaceae (Gentianales) in Tunisia: New Additions to National and North African Flora with Nomenclatural Updates and Taxonomic Notes

A taxonomic revision of the family Apocynaceae (Gentianales) from Tunisia is presented. Field surveys carried out during the last two decades allowed us to identify new records at the national level, i.e., Asclepias curassavica, Carissa macrocarpa, Cascabela thevetia, and Cryptostegia grandiflora (the latter three are new to the non-native Mediterranean and North African woody vascular flora). The genus Asclepias is new at a national level, whereas Carissa, Cascabela, and Cryptostegia are recorded here for the first time in the Mediterranean basin. Information is provided about nomenclature (accepted names, main synonyms, and types), morphology, chromosome number, chorology, occurrence in Tunisia, habitat, phenology, and taxonomic annotations, and original photos are prepared. Diagnostic keys relating to generic and species ranks are also given. Using typificitions, the identity of the Linnaean names Cynanchum erectum and C. monspeliensis, Pourret's Vinca difformis, and Roxburgh's Nerium grandiflorum is discussed.

Navigating commensal dysbiosis: Gastrointestinal host-pathogen interplay orchestrating opportunistic infections

The gut commensals, which are usually symbiotic or non-harmful bacteria that live in the gastrointestinal tract, have a positive impact on the health of the host. This review, however, specifically discuss distinct conditions where commensals aid in the development of pathogenic opportunistic infections. We discuss that the categorization of gut bacteria as either pathogens or non-pathogens depends on certain circumstances, which are significantly affected by the tissue microenvironment and the dynamic host-microbe interaction. Under favorable circumstances, commensals have the ability to transform into opportunistic pathobionts by undergoing overgrowth. These conditions include changes in the host's physiology, simultaneous infection with other pathogens, effective utilization of nutrients, interactions between different species of bacteria, the formation of protective biofilms, genetic mutations that enhance pathogenicity, acquisition of genes associated with virulence, and the ability to avoid the host's immune response. These processes allow commensals to both initiate infections themselves and aid other pathogens in populating the host. This review highlights the need of having a detailed and sophisticated knowledge of the two-sided nature of gut commensals. Although commensals mostly promote health, they may also become harmful in certain changes in the environment or the body's functioning. This highlights the need of acknowledging the intricate equilibrium in interactions between hosts and microbes, which is crucial for preserving intestinal homeostasis and averting diseases. Finally, we also emphasize the further need of research to better understand and anticipate the behavior of gut commensals in different situations, since they play a crucial and varied role in human health and disease.

Oleander attenuates hepatic inflammation in a TLR4-independent manner and by favorable modulation of hepatocellular global metabolome that supports cytoprotection

ETHNOPHARMACOLOGICAL RELEVANCE

Nerium oleander is used to treat liver-associated chronic metabolic diseases in traditional medicinal systems across the globe. The hepatoprotective effects of oleander are mentioned in Indian and Chinese traditional medicinal literature.

AIM OF THE STUDY

The present study aimed to investigate the cellular mechanisms behind the hepatoprotective effects of a non-toxic dose of oleander (NO).

MATERIALS AND METHODS

The hepatoprotective effects of NO were tested against lipopolysaccharide (LPS)-treated HepG2 cells. Oxidative stress response was studied using cellular enzymatic assays, and gene expression was analyzed using qRT-PCR. HepG2 cells were pretreated with TAK-242 (pharmacological inhibitor of TLR4) to decipher the anti-inflammatory mechanisms of NO. Cell-free metabolites were analyzed using GCMS and were subjected to pathway enrichment analysis.

RESULTS

NO reduced systemic inflammation, serum lipid peroxidation byproducts, and glucose without affecting serum transaminase levels and hepatic histopathological features. NO attenuated the inflammation-induced loss of antioxidant enzyme activities and mRNA expressions of toll-like receptor-4 (TLR4)/nuclear factor κβ (NFκβ)-dependent inflammatory genes. In TAK-242 pretreated cells, LPS was unable to induce inflammatory and oxidative responses. However, NO treatment in TAK-242 pretreated cells with LPS stimulation further reduced the signs of inflammation and improved hepatoprotective activities. A comparative analysis of the intracellular global metabolome from HepG2 cells with and without NO treatment indicated NO-mediated favorable modulation of intracellular metabolic pathways that support cytoprotective activities.

CONCLUSION

NO protects HepG2 cells from LPS-induced oxidative and inflammatory injury. The hepatoprotective effects of NO are mediated by a TLR4-independent process and through a favorable modulation of the intracellular global metabolome that supports cytoprotection.

The intestinal-level metabolic benefits of green tea catechins: Mechanistic insights from pre-clinical and clinical studies

BACKGROUND

The intestinal-level host-microbiota interaction has been implicated in the pathogenesis of chronic diseases. The current review is intended to provide a comprehensive insight into deciphering whether intestinal-level bioactivities mediate the overall metabolic health benefits of green tea catechins.

PURPOSE

We have comprehensively discussed pre-clinical and clinical evidences of intestinal-level changes in metabolism, microbiota, and metabolome due to catechin-rich green tea treatments, ultimately limiting metabolic diseases. Exclusive emphasis has been given to purified catechins and green tea, and discussions on extraintestinal mechanisms of metabolic health benefits were avoided.

METHODS

A literature search for relevant pre-clinical and clinical studies was performed in various online databases (e.g., PubMed) using specific keywords (e.g., catechin, intestine, microbiota). Out of all the referred literature, ∼15% belonged to 2021-2023, ∼51% were from 2011-2020, and ∼32% from 2000-2010.

RESULT

The metabolic health benefits of green tea catechins are indeed influenced by the intestinal-level bioactivities, including reduction of mucosal inflammation and oxidative stress, attenuation of gut barrier dysfunction, decrease in intestinal lipid absorption and metabolism, favorable modulation of mucosal nuclear receptor signaling, alterations of the luminal global metabolome, and mitigation of the gut dysbiosis. The results from the recent clinical studies support the pre-clinical evidences. The challenges and pitfalls of the currently available knowledge on catechin bioactivities have been discussed, and constructive directions to harness the translational benefits of green tea through future interventions have been provided.

CONCLUSION

The metabolism, metabolome, and microbiota at the intestinal epithelia play critical roles in catechin metabolism, pharmacokinetics, bioavailability, and bioactivities. Especially the reciprocal interaction between the catechins and the gut microbiota dictates the metabolic benefits of catechins.

Rise of the guardians: Gut microbial maneuvers in bacterial infections

AIMS

Bacterial infections are one of the major causes of mortality globally. The gut microbiota, primarily comprised of the commensals, performs an important role in maintaining intestinal immunometabolic homeostasis. The current review aims to provide a comprehensive understanding of how modulation of the gut microbiota influences opportunistic bacterial infections.

MATERIALS AND METHODS

Primarily centered around mechanisms related to colonization resistance, nutrient, and metabolite-associated factors, mucosal immune response, and commensal-pathogen reciprocal interactions, we discuss how gut microbiota can promote or prevent bacterial infections.

KEY FINDINGS

Opportunistic infections can occur directly due to obligate pathogens or indirectly due to the overgrowth of opportunistic pathobionts. Gut microbiota-centered mechanisms of altered intestinal immunometabolic and metabolomic homeostasis play a significant role in infection promotion and prevention. Depletion in the population of commensals, increased abundance of pathobionts, and overall decrease in gut microbial diversity and richness caused due to prolonged antibiotic use are risk factors of opportunistic bacterial infections, including infections from multidrug-resistant spp. Gut commensals can limit opportunistic infections by mechanisms including the production of antimicrobials, short-chain fatty acids, bile acid metabolism, promoting mucin formation, and maintaining immunological balance at the mucosa. Gut microbiota-centered strategies, including the administration of probiotics and fecal microbiota transplantation, could help attenuate opportunistic bacterial infections.

SIGNIFICANCE

The current review discussed the gut microbial population and function-specific aspects contributing to bacterial infection susceptibility and prophylaxis. Collectively, this review provides a comprehensive understanding of the mechanisms related to the dual role of gut microbiota in bacterial infections.

A toxic shrub turned therapeutic: The dichotomy of Nerium oleander bioactivities

Nerium oleander L. is a medicinal plant, used for the treatment of cancers and hyperglycemia across the world, especially in Indian sub-continent, Turkey, Morocco, and China. Although clinical studies supporting its pharmacological effects remain critically underexplored, accidental and intentional consumption of any part of the plant causes fatal toxicity in animals and humans. While the polyphenolic fraction of oleander leaves has been attributed to its pre-clinical pharmacological activities, the presence of diverse cardiac glycosides (especially oleandrin) causes apoptosis to cancer cells in vitro and results in clinical signs of oleander poisoning. Thus, the dual pharmacological and toxicological role of oleander is a perplexing dichotomy in phytotherapy. The current investigative review, therefore, intended to analyze the intrinsic and extrinsic factors that likely contribute to this conundrum. Especially by focusing on gut microbial diversity, abundance, and metabolic functions, oleander-associated pharmacological and toxicological studies have been critically analyzed to define the dual effects of oleander. Electronic databases were extensively screened for relevant research articles (including pre-clinical and clinical) related to oleander bioactivities and toxicity. Taxonomic preference was given to the plant N. oleander L. and synonymous plants as per 'The World Flora Online' database (WCSP record #135196). Discussion on yellow oleander (Cascabela thevetia (L.) Lippold) has intentionally been avoided since it is a different plant. The review indicates that the gut microbiota likely plays a key role in differentially modulating the pharmacological and toxicological effects of oleander. Other factors identified influencing the oleander bioactivities include dose and mode of treatment, cardiac glycoside pharmacokinetics, host-endogenous glycosides, plant material processing and phytochemical extraction methods, plant genotypic variations, environmental effects on the phytochemical quality and quantity, gene expression variations, host dietary patterns and co-morbidity, etc. The arguments proposed are also relevant to other medicinal plants containing toxic cardiac glycosides.

Complementary and Alternative Medicines in the Management of Heart Failure: A Scientific Statement From the American Heart Association

Complementary and alternative medicines (CAM) are commonly used across the world by diverse populations and ethnicities but remain largely unregulated. Although many CAM agents are purported to be efficacious and safe by the public, clinical evidence supporting the use of CAM in heart failure remains limited and controversial. Furthermore, health care professionals rarely inquire or document use of CAM as part of the medical record, and patients infrequently disclose their use without further prompting. The goal of this scientific statement is to summarize published efficacy and safety data for CAM and adjunctive interventional wellness approaches in heart failure. Furthermore, other important considerations such as adverse effects and drug interactions that could influence the safety of patients with heart failure are reviewed and discussed.

Interactions between gut microbiota and berberine, a necessary procedure to understand the mechanisms of berberine

Berberine (BBR), an isoquinoline alkaloid, has been found in many plants, such as Coptis chinensis Franch and Phellodendron chinense Schneid. Although BBR has a wide spectrum of pharmacological effects, its oral bioavailability is extremely low. In recent years, gut microbiota has emerged as a cynosure to understand the mechanisms of action of herbal compounds. Numerous studies have demonstrated that due to its low bioavailability, BBR can interact with the gut microbiota, thereby exhibiting altered pharmacological effects. However, no systematic and comprehensive review has summarized these interactions and their corresponding influences on pharmacological effects. Here, we describe the direct interactive relationships between BBR and gut microbiota, including regulation of gut microbiota composition and metabolism by BBR and metabolization of BBR by gut microbiota. In addition, the complex interactions between gut microbiota and BBR as well as the side effects and personalized use of BBR are discussed. Furthermore, we provide our viewpoint on future research directions regarding BBR and gut microbiota. This review not only helps to explain the mechanisms underlying BBR activity but also provides support for the rational use of BBR in clinical practice.

Oleandrin: A Systematic Review of its Natural Sources, Structural Properties, Detection Methods, Pharmacokinetics and Toxicology

Oleandrin is a highly lipid-soluble cardiac glycoside isolated from the plant Nerium oleander (Apocynaceae) and is used as a traditional herbal medicine due to its excellent pharmacological properties. It is widely applied for various disease treatments, such as congestive heart failure. Recently, oleandrin has attracted widespread attention due to its extensive anti-cancer and novel anti-viral effects. However, oleandrin has a narrow therapeutic window and exhibits various toxicities, especially typical cardiotoxicity, which is often fatal. This severe toxicity and low polarity have significantly hindered its application in the clinic. This review describes natural sources, structural properties, and detection methods of oleandrin. Based on reported poisoning cases and sporadic animal experiments, the pharmacokinetic characteristics of oleandrin are summarized, so as to infer some possible phenomena, such as enterohepatic circulation. Moreover, the relevant factors affecting the pharmacokinetics of oleandrin are analyzed, and some research approaches that may ameliorate the pharmacokinetic behavior of oleandrin are proposed. With the toxicology of oleandrin being thoroughly reviewed, the development of safe clinical applications of oleandrin may be possible given potential research strategies to decrease toxicity.

The intestinal 3M (microbiota, metabolism, metabolome) zeitgeist - from fundamentals to future challenges

The role of the intestine in human health and disease has historically been neglected and was mostly attributed to digestive and absorptive functions. In the past two decades, however, discoveries related to human nutrition and intestinal host-microbe reciprocal interaction have established the essential role of intestinal health in the pathogenesis of chronic diseases and the overall wellbeing. That transfer of gut microbiota could be a means of disease phenotype transfer has revolutionized our understanding of chronic disease pathogenesis. This narrative review highlights the major concepts related to intestinal microbiota, metabolism, and metabolome (3M) that have facilitated our fundamental understanding of the association between the intestine, and human health and disease. In line with increased interest of microbiota-dependent modulation of human health by dietary phytochemicals, we have also discussed the emerging concepts beyond the phytochemical bioactivities which emphasizes the integral role of microbial metabolites of parent phytochemicals at extraintestinal tissues. Finally, this review concludes with challenges and future prospects in defining the 3M interactions and has emphasized the fact that, it takes 'guts' to stay healthy.

Antibacterial kinetics and phylogenetic analysis of Aloe vera plants

Uncontrolled use of antibiotics has resulted in the emergence of resistant bacteria. It has necessitated the evaluation of antibacterial activities and phylo-diversity of Aloe vera (also called Aloe barbadensis) plants as antimicrobial agent in Nigeria. Biotyped enteric bacilli of 251 strains obtained from fecal samples of patients with various gastro-intestinal complications are profiled for antibiogram. Resistant biotypes were assayed for susceptibility to Aloe vera latex and further evaluated for time-kill kinetics and phylo-diversity. More than 30% of enteric bacilli, including Citrobacter freundii, Escherichia coli and Proteus mirabilis were resistant to cotrimoxazole, ciprofloxacin, and tetracycline respectively at MIC >16 µg/ml (p=0.004). Aloe vera latex significantly inhibited 39.5% resistant enteric biotypes with a significant average reduction of the viable count at 1xMIC and 2xMIC to less than 3.0 Log10CFU/mL after 24 hours. Flavonoids, alkaloids, terpenoids and anthraquinine in anti-enteric sap significantly correlated and regressed with antibacterial activity (p<0.05), while two of the antimicrobial Aloe vera plants showed phylogenetic relatedness with other homologous. Anti-bacteria efficacy of some Nigerian Aloe vera latex could provide alternative therapy, while its phylo-diversity and genomic profiling would offer a promising avenue for identification and development of antimicrobial agents as drug candidates for natural antibiotics.

Antiinflammatory phytochemicals against virus-induced hyperinflammatory responses: Scope, rationale, application, and limitations

Uncontrolled inflammatory responses or cytokine storm associated with viral infections results in deleterious consequences such as vascular leakage, severe hemorrhage, shock, immune paralysis, multi-organ failure, and even death. With the emerging new viral infections and lack of effective prophylactic vaccines, evidence-based complementary strategies that limit viral infection-mediated hyperinflammatory responses could be a promising approach to limit host tissue injury. The present review emphasizes the potentials of antiinflammatory phytochemicals in limiting hyperinflammatory injury caused by viral infections. The predominant phytochemicals along with their mechanism in limiting hyperimmune and pro-inflammatory responses under viral infection have been reviewed comprehensively. How certain phytochemicals can be effective in limiting hyper-inflammatory response indirectly by favorably modulating gut microbiota and maintaining a functional intestinal barrier has also been presented. Finally, we have discussed improved systemic bioavailability of phytochemicals, efficient delivery strategies, and safety measures for effective antiinflammatory phytotherapies, in addition to emphasizing the requirement of tightly controlled clinical studies to establish the antiinflammatory efficacy of the phytochemicals. Collectively, the review provides a scooping overview on the potentials of bioactive phytochemicals to mitigate pro-inflammatory injury associated with viral infections.

A comprehensive review of herbacetin: From chemistry to pharmacological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Herbacetin is an active constituent of traditional Chinese medicines such as Ephedra sinica Stapf (MaHuang) and Sedum roseum (L.). Scop. (Hong JingTian). MaHuang was used to treat cough, asthma, fever, and edema for more than 5000 years, while Hong JingTian was used to treat depression, fatigue, cancers, and cardiovascular disease. Recent studies indicate that herbacetin and its glycosides play a critical role in the pharmacological activities of these herbs. However, currently, no comprehensive review on herbacetin has been published yet.

AIM OF THE STUDY

This review aimed to summarize information on the chemistry, natural sources, and pharmacokinetic features of herbacetin, with an emphasis on its pharmacological activities and possible mechanisms of action.

MATERIALS AND METHODS

A literature search was performed on the Web of Science, PubMed, and China Knowledge Resource Integrated databases (CNKI) using the search term "herbacetin" ("all fields") from 1935 to 2020. Information was also obtained from classic books of Chinese herbal medicine, Chinese pharmacopeia, and the database "The Plant List" (www.theplantlist.org). Studies have been analyzed and summarized in this review if they dealt with chemistry, taxonomy, pharmacokinetic, and pharmacological activity.

RESULTS

Herbacetin is distributed in various plants and can be extracted or synthesized. It showed diverse pharmacological activities including antioxidant, antiviral, anti-inflammatory, anticancer, antidiabetic, and anticholinesterase. It is thought to have great potential in cancer treatment, especially colon and skin cancers. However, the bioavailability of herbacetin is low and the toxicity of herbacetin has not been studied. Thus, more studies are required to solve these problems.

CONCLUSIONS

Herbacetin shows promising pharmacological activities against multiple diseases. Future research should focus on improving bioavailability, further studying its pharmacological mechanism, evaluating its toxicity and optimal dose, and performing the clinical assessment. We hope that the present review will serve as a guideline for future research on herbacetin.

Targeting gut barrier dysfunction with phytotherapies: Effective strategy against chronic diseases

The intestinal epithelial layer serves as a physical and functional barrier between the microbe-rich lumen and immunologically active submucosa; it prevents systemic translocation of microbial pyrogenic products (e.g. endotoxin) that elicits immune activation upon translocation to the systemic circulation. Loss of barrier function has been associated with chronic 'low-grade' systemic inflammation which underlies pathogenesis of numerous no-communicable chronic inflammatory disease. Thus, targeting gut barrier dysfunction is an effective strategy for the prevention and/or treatment of chronic disease. This review intends to emphasize on the beneficial effects of herbal formulations, phytochemicals and traditional phytomedicines in attenuating intestinal barrier dysfunction. It also aims to provide a comprehensive understanding of intestinal-level events leading to a 'leaky-gut' and systemic complications mediated by endotoxemia. Additionally, a variety of detectable markers and diagnostic criteria utilized to evaluate barrier improving capacities of experimental therapeutics has been discussed. Collectively, this review provides rationale for targeting gut barrier dysfunction by phytotherapies for treating chronic diseases that are associated with endotoxemia-induced systemic inflammation.

The role of gut microbiome in chemical-induced metabolic and toxicological murine disease models

The role of gut microbiome in human health and disease is well established. While evidence-based pharmacological studies utilize a variety of chemical-induced metabolic and toxicological disease models that in part recapitulate the natural mode of disease pathogenesis, the mode of actions of these disease models are likely underexplored. Conventionally, the mechanistic principles of these disease models are established as direct tissue toxicity through redox imbalance and pro-inflammatory injury. However, emerging evidences suggest that the mode of action of these chemicals could be largely associated with changes in gut microbial populations, diversity and metabolic functions, affecting pathological changes along the gut-liver and gut-pancreas axis. Especially in these disease models, reversal of disease severity or less sensitivity to induced disease pathogenesis has been observed when germ-free or antibiotic-supplemented microbiota-depleted rodents were treated with disease causing chemicals. Thus, by summarizing evidences from in vivo pharmacological interventions, this review revisits the mode of action of carbon tetrachloride-induced cirrhosis, diethylnitrosamine-induced hepatocellular carcinoma, acetaminophen-induced hepatotoxicity and alloxan- and streptozotocin-induced diabetes through the light of gut microbiota. How changes in gut microbiome affects tissue-level toxicity likely through intestinal-level mechanisms like gastrointestinal inflammation and gut barrier dysfunction has also been discussed. Additionally, this review discusses potential pitfalls of inconsistent experimental models that precludes defining the gut microbial effects in evidence-based pharmacology. Collectively, this review emphasizes the underexplored role of microbial intervention in experimental pharmacology and aims to provide direction towards redefining and establishing microbiome-centric alternative mode of action of chemical-induced metabolic and toxicological disease models in pharmacological research.

Cytotoxicity of Oleandrin Is Mediated by Calcium Influx and by Increased Manganese Uptake in Saccharomyces cerevisiae Cells

Oleandrin, the main component of Nerium oleander L. extracts, is a cardiotoxic glycoside with multiple pharmacological implications, having potential anti-tumoral and antiviral characteristics. Although it is accepted that the main mechanism of oleandrin action is the inhibition of Na⁺/K⁺-ATPases and subsequent increase in cell calcium, many aspects which determine oleandrin cytotoxicity remain elusive. In this study, we used the model Saccharomyces cerevisiae to unravel new elements accounting for oleandrin toxicity. Using cells expressing the Ca²⁺-sensitive photoprotein aequorin, we found that oleandrin exposure resulted in Ca²⁺ influx into the cytosol and that failing to pump Ca²⁺ from the cytosol to the vacuole increased oleandrin toxicity. We also found that oleandrin exposure induced Mn²⁺ accumulation by yeast cells via the plasma membrane Smf1 and that mutants with defects in Mn²⁺ homeostasis are oleandrin-hypersensitive. Our data suggest that combining oleandrin with agents which alter Ca²⁺ or Mn²⁺ uptake may be a way of controlling oleandrin toxicity.