The therapeutic and protective effects of bee pollen against prenatal methylmercury induced neurotoxicity in rat pups

Translational Research on Bee Pollen as a Source of Nutrients: A Scoping Review from Bench to Real World

The emphasis on healthy nutrition is gaining a forefront place in current biomedical sciences. Nutritional deficiencies and imbalances have been widely demonstrated to be involved in the genesis and development of many world-scale public health burdens, such as metabolic and cardiovascular diseases. In recent years, bee pollen is emerging as a scientifically validated candidate, which can help diminish conditions through nutritional interventions. This matrix is being extensively studied, and has proven to be a very rich and well-balanced nutrient pool. In this work, we reviewed the available evidence on the interest in bee pollen as a nutrient source. We mainly focused on bee pollen richness in nutrients and its possible roles in the main pathophysiological processes that are directly linked to nutritional imbalances. This scoping review analyzed scientific works published in the last four years, focusing on the clearest inferences and perspectives to translate cumulated experimental and preclinical evidence into clinically relevant insights. The promising uses of bee pollen for malnutrition, digestive health, metabolic disorders, and other bioactivities which could be helpful to readjust homeostasis (as it is also true in the case of anti-inflammatory or anti-oxidant needs), as well as the benefits on cardiovascular diseases, were identified. The current knowledge gaps were identified, along with the practical challenges that hinder the establishment and fructification of these uses. A complete data collection made with a major range of botanical species allows more robust clinical information.

Neurotransmitter disturbances caused by methylmercury exposure: Microbiota-gut-brain interaction

The fetal and early postnatal stages are periods of rapid brain development, during which, methylmercury (MeHg) exposure can cause lasting cognitive impairments. MeHg exposure disrupts neurotransmitter metabolites, which increased susceptibility to neurological responses. However, the neurotoxic mechanism underlying the MeHg-induced disruption of neurotransmitter metabolism requires further exploration. To this end, female Sprague-Dawley (SD) rats were administered NaCl (control group) or MeHg (0.6 mg/kg, 1.2 mg/kg and 2.4 mg/ kg body weight (bw), where the body weight refers to the dams) during the perinatal period, and then changes in neurotransmitter profiles and the gut microbiota of offspring were detected. The results showed that tryptophan (Trp) and tyrosine (Tyr) pathway neurotransmitter metabolites, including serotonin (5-HT), 5-hydroxy indole acetic acid (5-HIAA), N-acetyl-5-hydroxytryptamin (NAS), Tyr, dopamine (DA) and epinephrine (E), were significantly changed, and the Kynurenine/Tryptophan (Kyn/Trp) ratio was increased in the MeHg-treated groups. Meanwhile, acetylcholine (ACh) and neurotransmitters involved in the amino acid pathway were significantly reduced. Notably, MeHg treatment induced a significant reduction in tight junctions in the colon and hippocampal tissue. Furthermore, fecal microbiota analysis indicated that the diversity and composition characteristics were significantly altered by MeHg exposure. Mediation analysis showed that the gut microbiota mediated the effect of MeHg treatment on the neurotransmitter expression profiles. The present findings shed light on the regulatory role of the gut microbiota in MeHg-disrupted neurotransmitter metabolic pathways and the potential impact of perinatal MeHg treatment on the "cross-talk" between the gut and brain.

Subchronic Low-Dose Methylmercury Exposure Accelerated Cerebral Telomere Shortening in Relevant with Declined Urinary aMT6s Level in Rats

Methylmercury (MeHg) is a global pollutant with established toxic effects on the central nervous system (CNS). However, early events and early-warning biomarkers of CNS damage following exposure to low-dose MeHg are still lacking. This study aimed to investigate whether subchronic low-dose MeHg exposure had adverse effects on the cerebral telomere length, as well as serum melatonin and its urinary metabolite 6-sulfatoxymelatonin (aMT6s) in rats. Sixteen male Sprague Dawley rats were divided into two groups. Group I was the control group. In group II, rats were exposed to MeHg by gavage at a dose of 0.1 mg/kg/day for 3 months. This study revealed that MeHg exposure resulted in impairment of learning and memory ability, a slightly reduced number of neurons and an irregular arrangement of neurons in the hippocampus. It also significantly accelerated telomere shortening in the cerebral cortex, hippocampus and hypothalamus. Moreover, MeHg exposure decreased the levels of melatonin in serum and aMT6s in urine, partly by suppressing the synthesis of 5-hydroxytryptamine (5-HT) in the brain but promoted the expression of melatonin-catalyzing AANAT and ASMT. Importantly, cerebral telomere length was positively correlated with MT and aMT6s after MeHg exposure. These results suggested that the shortened telomere length in the brain may be an early event in MeHg-induced CNS toxicity, and the level of aMT6s in urine may serve as an early-warning biomarker for MeHg-induced CNS damage.

Advances on the Influence of Methylmercury Exposure during Neurodevelopment

Mercury (Hg) is a toxic heavy-metal element, which can be enriched in fauna and flora and transformed into methylmercury (MeHg). MeHg is a widely distributed environmental pollutant that may be harmful to fish-eating populations through enrichment of aquatic food chains. The central nervous system is a primary target of MeHg. Embryos and infants are more sensitive to MeHg, and exposure to MeHg during gestational feeding can significantly impair the homeostasis of offspring, leading to long-term neurodevelopmental defects. At present, MeHg-induced neurodevelopmental toxicity has become a hotspot in the field of neurotoxicology, but its mechanisms are not fully understood. Some evidence point to oxidative damage, excitotoxicity, calcium ion imbalance, mitochondrial dysfunction, epigenetic changes, and other molecular mechanisms that play important roles in MeHg-induced neurodevelopmental toxicity. In this review, advances in the study of neurodevelopmental toxicity of MeHg exposure during pregnancy and the molecular mechanisms of related pathways are summarized, in order to provide more scientific basis for the study of neurodevelopmental toxicity of MeHg.

Bee pollen increases hippocampal brain-derived neurotrophic factor and suppresses neuroinflammation in adult rats with chronic immobilization stress

Chronic stress is a potential problem associated with anxiety, depression, and cognitive dysfunction. Bee pollen, a powerful antioxidant, has many therapeutic effects. In this study, we aimed to examine the effects of one of the Anatolian bee pollens on depression/anxiety. 24 male Sprague Dawley rats were divided into 3 groups as control, stress, and bee pollen + stress. Bee pollen (200 mg/kg/day) was given to rats exposed to physical stress for 10 days. Open field test (OFT) and forced swimming test (FST) were applied to monitor the behavioral changes of the rats. After behavioral tests, the rats were euthanized. Brain-derived neurotrophic factor (BDNF), interleukin 1 beta (IL-1β), and tumor necrosis factor-alpha (TNF-α) levels were measured by ELISA to evaluate neurological and biochemical changes in rat hippocampal tissue. In addition, malondialdehyde (MDA) and glutathione (GSH) levels in the brain were evaluated. According to the behavioral test results, bee pollen reduced anxiety-like behavior but did not affect depression-like behavior. We also found that bee pollen suppressed neuroinflammation while reducing oxidative stress and lipid peroxidation in hippocampal tissues. Moreover, bee pollen significantly increased the level of BDNF in the hippocampus. In conclusion, bee pollen reduced oxidative damage and neuroinflammation caused by immobilization stress in rat brain tissue. Therefore, we suggest that bee pollen may be an effective natural compound in alleviating the negative effects caused by immobilization stress.

Psychobiotics improve propionic acid-induced neuroinflammation in juvenile rats, rodent model of autism

This study aimed to evaluate the protective and therapeutic potency of bee pollen and probiotic mixture on brain intoxication caused by propionic acid (PPA) in juvenile rats. Five groups of six animals each, were used: the control group only receiving phosphate-buffered saline; the bee pollen and probiotic-treated group receiving a combination of an equal quantity of bee pollen and probiotic (0.2 kg/kg body weight); the PPA group being treated for 3 days with an oral neurotoxic dose of PPA (0.25 kg/kg body weight); the protective and therapeutic groups receiving bee pollen and probiotic mixture treatment right before and after the neurotoxic dose of PPA, respectively. The levels of interleukin (IL)-1ß, IL-6, IL-8, IL-10, IL-12, tumor necrosis factor α, and interferon γ (IFN-γ) were investigated to evaluate the neuroinflammatory responses in brain tissues from different animal groups. The much higher IL-1β, IL-8, and IFN-γ, as pro-inflammatory cytokines (P < 0.001), together with much lower IL-10, as anti-inflammatory cytokine (P < 0.001) compared to controls clearly demonstrated the neurotoxic effects of PPA. Interestingly, the mixture of bee pollen and probiotics was effective in alleviating PPA neurotoxic effects in both therapeutic and protective groups demonstrating highly significant changes in IL-1β, IL-8, IL-10, and IFN-γ levels together with non-significant reduction in IL-6 levels compared to PPA-treated rats. Overall, our findings demonstrated a new approach to the beneficial use of psychobiotics presenting as bee pollen and probiotic combination in neuroinflammation through cytokine changes as a possible role of glial cells in gut–brain axis.

Testing the combined effects of probiotics and prebiotics against neurotoxic effects of propionic acid orally administered to rat pups

The present study investigated the combined effects of mixed probiotic and bee pollen on brain intoxication induced by propionic acid (PPA) in rat pups. Thirty western albino rats were divided into five groups, six animals each: (1) Control group receiving phosphate-buffered saline; (2) Probiotic and bee pollen-treated group being administered at the same dose with 200 mg/kg body weight; (c) PPA-treated group receiving a neurotoxic dose 250 mg/kg body weight of PPA for 3 days; (d) Therapeutic group being administered the neurotoxic dose of PPA followed by probiotic and bee pollen treatment 200 mg/kg body weight; (e) Protective group receiving probiotic and bee pollen mixture treatment followed by neurotoxic dose of PPA. Selected biochemical parameters linked to oxidative stress, energy metabolism, and neurotransmission were investigated in brain homogenates from all the five groups. PPA treatment showed an increase in oxidative stress markers like lipid peroxidation coupled with a significant decrease in glutathione level. Impaired energy metabolism was ascertained via the alteration of creatine kinase (CK) and lactate dehydrogenase (LDH) activities. Dramatic increase of Na+ and K+ concentrations together with a decrease of GABA and IL-6 and an elevation of glutamate levels in PPA-treated rat's pups confirmed the neurotoxicity effect of PPA. Interestingly, the mixed probiotic and bee pollen treatment were effective in restoring the levels of glutamate, GABA, and IL-6 in addition to normalizing the levels of lipid peroxidation and glutathione and the activities of CK and LDH. The present study indicates that mixed probiotic and bee pollen treatment can improve poor detoxification, oxidative stress, and neuroinflammation as mechanisms implicated in the etiology of autism.

Mechanisms of oxidative stress in methylmercury-induced neurodevelopmental toxicity

Methylmercury (MeHg) is a long-lasting organic environmental pollutant that poses a great threat to human health. Ingestion of seafood containing MeHg is the most important way by which it comes into contact with human body, where the central nervous system (CNS) is the primary target of MeHg toxicity. During periods of pre-plus postnatal, in particular, the brain of offspring is vulnerable to specific developmental insults that result in abnormal neurobehavioral development, even without symptoms in mothers. While many studies on neurotoxic effects of MeHg on the developing brain have been conducted, the mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity is less clear. Hitherto, no single process can explain the many effects observed in MeHg-induced neurodevelopmental toxicity. This review summarizes the possible mechanisms of oxidative stress in MeHg-induced neurodevelopmental toxicity, highlighting modulation of Nrf2/Keap1/Notch1, PI3K/AKT, and PKC/MAPK molecular pathways as well as some preventive drugs, and thus contributes to the discovery of endogenous and exogenous molecules that can counteract MeHg-induced neurodevelopmental toxicity.

Immunomodulatory effects of bee pollen on doxorubicin-induced bone marrow/spleen immunosuppression in rat

This study investigated the immunomodulatory effects of Bee Pollen (BP) on Doxorubicin (DOX)-induced bone marrow/spleen suppression in rats. 48 Wistar rats were divided into 6 groups (n = 8/group); control, DOX (5 mg/kg), BP (100 mg/kg), BP (200 mg/kg), BP (100 mg/kg) +DOX, and BP (200 mg/kg) +DOX groups. BP was administered orally for 42 days and 5 mg/kg of DOX was injected intravenously at days 7, 14, 21, 28, 35 and 42. Hematological parameters, antioxidant enzymes and inflammatory cytokines were measured. Apoptosis-related genes were investigated using Real-Time PCR and western blot. DOX significantly decreased blood cells count, cytokines, and antioxidant enzyme. It also increased the expression of apoptotic genes in spleen and BM. The BP significantly improved hematopoietic function, antioxidant parameters, and serum levels of hematopoietic simulating-cytokines. Also, BP significantly reduced the expression of apoptotic genes. These results confirm the immunomodulatory activity of BP in DOX-induced biochemical, molecular and histological immunosuppression. PRACTICAL APPLICATIONS: Chemotherapy drugs are being developed every day but are limited due to their side effects. The most important side effect of chemotherapy drugs is the suppression of hematopoiesis through its direct effect on bone marrow and hematopoietic cells. Today, many studies are done on natural, synthetic and semi-synthetic compounds to reduce the effects of chemotherapy drugs. Compounds that, along with chemotherapy drugs in the treatment of various tumors, maintain the hematopoietic pathway, synergize the antitumor effects of chemotherapy drugs, and also protect other organs of the body from free radical damage produced by chemotherapy drugs. One of these natural compounds is bee pollen, which has all the properties mentioned in chemotherapy supplements and can be used in the pharmaceutical industry.

Safflospermidines from the bee pollen of Helianthus annuus L. exhibit a higher in vitro antityrosinase activity than kojic acid

Background

Ozone deterioration in the atmosphere has become a severe problem causing overexposure of ultraviolet light, which results in humans in melanin overproduction and can lead to many diseases, such as skin cancer and melasma, as well as undesirable esthetic appearances, such as freckles and hyperpigmentation. Although many compounds inhibit melanin overproduction, some of them are cytotoxic, unstable, and can cause skin irritation. Thus, searching for new natural compounds with antityrosinase activity and less/no side effects is still required. Here, bee pollen derived from sunflower (Helianthus annuus L.) was evaluated.

Materials and methods

Sunflower bee pollen (SBP) was collected from Apis mellifera bees in Lopburi province, Thailand in 2017, extracted by methanol and sequentially partitioned with hexane and dichloromethane (DCM). The in vitro antityrosinase activity was evaluated using mushroom tyrosinase and the half maximal inhibitory concentration (IC₅₀) is reported. The antioxidation activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and reported as the half maximal effective concentration. Two pure compounds with antityrosinase activity were isolated by silica gel 60 column chromatography (SG₆₀CC) and high performance liquid chromatography (HPLC), and their chemical structure deduced by Nuclear Magnetic Resonance (NMR) analysis.

Results

The DCM partitioned extract of SBP (DCMSBP) had an antityrosinase activity (IC₅₀, 159.4 μg/mL) and was fractionated by SG₆₀CC, providing five fractions (DCMSBP1-5). The DCMSBP5 fraction was the most active (IC₅₀ = 18.8 μg/mL) and further fractionation by HPLC gave two active fractions, revealed by NMR analysis to be safflospermidine A and B. Interestingly, both safflospermidine A and B had a higher antityrosinase activity (IC₅₀ of 13.8 and 31.8 μM, respectively) than kojic acid (IC₅₀ of 44.0 μM). However, fraction DCMSBP5 had no significant antioxidation activity, while fractions DCMSBP1-4 showed a lower antioxidation activity than ascorbic acid.

Conclusion

Safflospermidine A and B are potential natural tyrosinase inhibitors.