Neuroprotective Impact of Linagliptin against Cadmium-Induced Cognitive Impairment and Neuropathological Aberrations: Targeting SIRT1/Nrf2 Axis, Apoptosis, and Autophagy

Study on the mechanism of activating SIRT1/Nrf2/p62 pathway to mediate autophagy-dependent ferroptosis to promote healing of diabetic foot ulcers

Diabetic foot (DF), a prevalent and grave diabetes sequela, is considered as a notable clinical concern, with SIRT1 downregulation observed in DF patients' blood specimens. Nonetheless, the regulatory mechanisms of SIRT1 in diabetic foot ulcer (DFU) remain unclear. Thus, in the current study, we investigated the role and mechanisms of SIRT1 in alleviating DFU. Western blotting was used to detect the expression of autophagy and ferroptosis-related proteins, CCK8 assay was used to measure cell proliferation. Plate colony method was used to measure bacterial growth, and the inhibitory effect on intracellular and extracellular Staphylococcus aureus was observed after drug intervention. ELISA was used to detect inflammatory cytokines and oxidative stress markers levels. ROS, total iron, and Fe2+ levels were detected using corresponding assays. Additionally, HE staining detected the thickness of the epidermis and dermis of the rat wound tissue while the collagen deposition in the wound tissue was detected using Masson staining. In addition, Prussian blue staining was used to detect iron deposition, and C11 BODIPY 581/591 lipid peroxidation probe was used to detect lipid ROS. Our results suggested that the activation of SIRT1/Nrf2/p62 signaling affects cell proliferation, colony formation, ferroptosis, and the production of lipid ROS in DFU-infected cell model through autophagy. In vivo experiments indicated that activating SIRT1/Nrf2/p62 signaling affects oxidative stress, inflammation, and autophagy in wound tissue and promotes wound healing in DFU rats through mediating autophagy-dependent ferroptosis. Taken together, the activation of SIRT1/Nrf2/p62 pathway can promote DFU healing, which might be mediated by autophagy-dependent ferroptosis.

Omarigliptin/rosinidin combination ameliorates cyclophosphamide-induced lung toxicity in rats: The interaction between glucagon-like peptide-1, TXNIP/NLRP3 inflammasome signaling, and PI3K/Akt/FoxO1 axis

Cyclophosphamide is an anti-neoplastic drug that has shown competence in the management of a broad range of malignant tumors. In addition, it represents a keystone agent for management of immunological conditions. Despite these unique properties, induction of lung toxicity may limit its clinical use. Omarigliptin is one of the dipeptidyl peptidase-4 inhibitors that has proven efficacy in management of diabetes mellitus. Rosinidin is an anthocyanidin flavonoid that exhibited promising results in management of diseases characterized by oxidative stress, inflammation, and apoptosis. The present work investigated the possible effects of omarigliptin with or without rosinidin on cyclophosphamide-induced lung toxicity with an exploration of the molecular mechanisms that contribute to these effects. In a rodent model of cyclophosphamide elicited lung toxicity, the potential efficacy of omarigliptin with or without rosinidin was investigated at both the biochemical and the histopathological levels. Both omarigliptin and rosinidin exhibited a synergistic ability to augment the tissue antioxidant defenses, mitigate the inflammatory pathways, restore glucagon-like peptide-1 levels, modulate high mobility group box 1 (HMGB1)/receptors of advanced glycation end products (RAGE)/nuclear factor kappa B (NF-κB) axis, downregulate the fibrogenic mediators, and create a balance between the pathways involved in apoptosis and the autophagy signals in the pulmonary tissues. In conclusion, omarigliptin/rosinidin combination may be introduced as a novel therapeutic modality that attenuates the different forms of lung toxicities induced by cyclophosphamide.

Boswellic acid and apigenin alleviate methotrexate-provoked renal and hippocampal alterations in rats: Targeting autophagy, NOD-2/NF-κB/NLRP3, and connexin-43

The neuronal and renal deteriorations observed in patients exposed to methotrexate (MTX) therapy highlight the need for medical interventions to counteract these complications. Boswellic acid (BA) and apigenin (APG) are natural phytochemicals with prominent neuronal and renal protective impacts in various ailments. However, their impacts on MTX-provoked renal and hippocampal toxicity have not been reported. Thus, the present work is tailored to clarify the ability of BA and APG to counteract MTX-provoked hippocampal and renal toxicity. BA (250 mg/kg) or APG (20 mg/kg) were administered orally in rats once a day for 10 days, while MTX (20 mg/kg, i.p.) was administered once on the sixth day of the study. At the histopathological level, BA and APG attenuated MTX-provoked renal and hippocampal aberrations. They also inhibited astrocyte activation, as proven by the inhibition of glial fibrillary acidic protein (GFAP). These impacts were partially mediated via the activation of autophagy flux, as proven by the increased expression of beclin1, LC3-II, and the curbing of p62 protein, alongside the regulation of the p-AMPK/mTOR nexus. In addition, BA and APG displayed anti-inflammatory features as verified by the damping of NOD-2 and p-NF-κB p65 to reduce TNF-α, IL-6, and NLRP3/IL-1β cue. These promising effects were accompanied with a notable reduction in one of the gap junction proteins, connexin-43 (Conx-43). These positive impacts endorse BA and APG as adjuvant modulators to control MTX-driven hippocampal and nephrotoxicity.

Activation of AMPK/mTOR-Driven Autophagy and Suppression of the HMGB1/TLR4 Pathway with Pentoxifylline Attenuates Doxorubicin-Induced Hepatic Injury in Rats

Despite being an effective chemotherapeutic agent, the clinical use of doxorubicin (DOX) is limited by several organ toxicities including hepatic injury. Pentoxifylline (PTX) is a methylxanthine derivative with marked anti-inflammatory and anti-apoptotic features. It is unknown, however, whether PTX can mitigate DOX-evoked hepatotoxicity. This study aims to explore the potential hepatoprotective impact of PTX in DOX-induced hepatic injury and the underlying molecular mechanisms. Histopathology, immunohistochemistry, and ELISA were used to examine liver tissues. The current findings revealed that PTX administration to DOX-intoxicated rats mitigated the pathological manifestations of hepatic injury, reduced microscopical damage scores, and improved serum ALT and AST markers, revealing restored hepatic cellular integrity. These favorable effects were attributed to PTX's ability to mitigate inflammation by reducing hepatic IL-1β and TNF-α levels and suppressing the pro-inflammatory HMGB1/TLR4/NF-κB axis. Moreover, PTX curtailed the hepatic apoptotic abnormalities by suppressing caspase 3 activity and lowering the Bax/Bcl-2 ratio. In tandem, PTX improved the defective autophagy events by lowering hepatic SQSTM-1/p62 accumulation and enhancing the AMPK/mTOR pathway, favoring autophagy and hepatic cell preservation. Together, for the first time, our findings demonstrate the ameliorative effect of PTX against DOX-evoked hepatotoxicity by dampening the hepatic HMGB1/TLR4/NF-κB pro-inflammatory axis and augmenting hepatic AMPK/mTOR-driven autophagy. Thus, PTX could be utilized as an adjunct agent with DOX regimens to mitigate DOX-induced hepatic injury.

Linagliptin ameliorates tacrolimus-induced renal injury: role of Nrf2/HO-1 and HIF-1α/CTGF/PAI-1

BACKGROUND

Tacrolimus (TAC) is a frequently used immunosuppressive medication in organ transplantation. However, its nephrotoxic impact limits its long-term usage. This study aims to investigate the effect of linagliptin (Lina) on TAC-induced renal injury and its underlying mechanisms.

METHODS AND RESULTS

Thirty-two Sprague Dawley rats were treated with TAC (1.5 mg/kg/day, subcutaneously) and/or Lina (5 mg/kg/day, orally) for 4 weeks. Histological examination was conducted, and serum and urinary biomarkers were measured to assess kidney function and integrity. Furthermore, ELISA, Western blot analysis and immunohistochemical assay were employed to determine signaling molecules of oxidative stress, profibrogenic, hypoxic, and apoptotic proteins. Tacrolimus caused renal dysfunction and histological deterioration evidenced by increased serum creatinine, blood urea nitrogen (BUN), urinary cystatin C, and decreased serum albumin as well as elevated tubular injury and interstitial fibrosis scores. Additionally, TAC significantly increased the expression of collagen type-1, alpha-smooth muscle actin (α-SMA), plasminogen activator inhibitor-1 (PAI-1), and transforming growth factor-beta1 (TGF-β1) renal content. Moreover, TAC decreased the expression of nuclear factor erythroid-2-related factor2 (Nrf2), heme oxygenase 1 (HO-1), and mitochondrial superoxide dismutase (SOD2). In addition, TAC increased protein expression of hypoxia-inducible factor1-alpha (HIF-1α), connective tissue growth factor (CTGF), inducible nitric oxide synthase (iNOS), 8-hydroxy-2-deoxyguanosine (8-OHdG), as well as nitric oxide (NO), 4-hydroxynonenal, caspase-3 and Bax renal contents. Furthermore, TAC decreased Bcl-2 renal contents. The Lina administration markedly attenuated these alterations.

CONCLUSION

Lina ameliorated TAC-induced kidney injury through modulation of oxidative stress, hypoxia, and apoptosis related proteins.

Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute promotes bone regeneration by moderating oxidative stress in osteoporotic bone defect

The treatment of osteoporotic bone defect remains a big clinical challenge because osteoporosis (OP) is associated with oxidative stress and high levels of reactive oxygen species (ROS), a condition detrimental for bone formation. Anti-oxidative nanomaterials such as selenium nanoparticles (SeNPs) have positive effect on osteogenesis owing to their pleiotropic pharmacological activity which can exert anti-oxidative stress functions to prevent bone loss and facilitate bone regeneration in OP. In the current study a strategy of one-pot method by introducing Poly (lactic acid-carbonate) (PDT) and β-Tricalcium Phosphate (β-TCP) with SeNPs, is developed to prepare an injectable, anti-collapse, shape-adaptive and adhesive bone graft substitute material (PDT-TCP-SE). The PDT-TCP-SE bone graft substitute exhibits sufficient adhesion in biological microenvironments and osteoinductive activity, angiogenic effect and anti-inflammatory as well as anti-oxidative effect in vitro and in vivo. Moreover, the PDT-TCP-SE can protect BMSCs from erastin-induced ferroptosis through the Sirt1/Nrf2/GPX4 antioxidant pathway, which, in together, demonstrated the bone graft substitute material as an emerging biomaterial with potential clinical application for the future treatment of osteoporotic bone defect. STATEMENT OF SIGNIFICANCE: Injectable, anti-collapse, adhesive, plastic and bioactive bone graft substitute was successfully synthesized. Incorporation of SeNPs with PDT into β-TCP regenerated new bone in-situ by moderating oxidative stress in osteoporotic bone defects area. The PDT-TCP-SE bone graft substitute reduced high ROS levels in osteoporotic bone defect microenvironment. The bone graft substitute could also moderate oxidative stress and inhibit ferroptosis via Sirt1/Nrf2/GPX4 pathway in vitro. Moreover, the PDT-TCP-SE bone graft substitute could alleviate the inflammatory environment and promote bone regeneration in osteoporotic bone defect in vivo. This biomaterial has the advantages of simple synthesis, biocompatibility, anti-collapse, injectable, and regulation of oxidative stress level, which has potential application value in bone tissue engineering.

Linagliptin, a DPP-4 inhibitor, activates AMPK/FOXO3a and suppresses NFκB to mitigate the debilitating effects of diethylnitrosamine exposure in rat liver: Novel mechanistic insights

Accumulating evidence suggests that dysregulation of FOXO3a plays a significant role in the progression of various malignancies, including hepatocellular carcinoma (HCC). FOXO3a inactivation, driven by oncogenic stimuli, can lead to abnormal cell growth, suppression of apoptosis, and resistance to anticancer drugs. Therefore, FOXO3a emerges as a potential molecular target for the development of innovative treatments in the era of oncology. Linagliptin (LNGTN), a DPP-4 inhibitor known for its safe profile, has exhibited noteworthy anti-inflammatory and anti-oxidative properties in previous in vivo studies. Several potential molecular mechanisms have been proposed to explain these effects. However, the capacity of LNGTN to activate FOXO3a through AMPK activation has not been investigated. In our investigation, we examined the potential repurposing of LNGTN as a hepatoprotective agent against diethylnitrosamine (DENA) intoxication. Additionally, we assessed LNGTN's impact on apoptosis and autophagy. Following a 10-week administration of DENA, the liver underwent damage marked by inflammation and early neoplastic alterations. Our study presents the first experimental evidence demonstrating that LNGTN can reinstate the aberrantly regulated FOXO3a activity by elevating the nuclear fraction of FOXO3a in comparison to the cytosolic fraction, subsequent to AMPK activation. Moreover, noteworthy inactivation of NFκB induced by LNGTN was observed. These effects culminated in the initiation of apoptosis, the activation of autophagy, and the manifestation of anti-inflammatory, antiproliferative, and antiangiogenic outcomes. These effects were concomitant with improved liver function and microstructure. In conclusion, our findings open new avenues for the development of novel therapeutic strategies targeting the AMPK/FOXO3a signaling pathway in the management of chronic liver damage.

Sirtuins as Players in the Signal Transduction of Citrus Flavonoids

Sirtuins (SIRTs) belong to the family of nicotine adenine dinucleotide (NAD+)-dependent class III histone deacetylases, which come into play in the regulation of epigenetic processes through the deacetylation of histones and other substrates. The human genome encodes for seven homologs (SIRT1-7), which are localized into the nucleus, cytoplasm, and mitochondria, with different enzymatic activities and regulatory mechanisms. Indeed, SIRTs are involved in different physio-pathological processes responsible for the onset of several human illnesses, such as cardiovascular and neurodegenerative diseases, obesity and diabetes, age-related disorders, and cancer. Nowadays, it is well-known that Citrus fruits, typical of the Mediterranean diet, are an important source of bioactive compounds, such as polyphenols. Among these, flavonoids are recognized as potential agents endowed with a wide range of beneficial properties, including antioxidant, anti-inflammatory, hypolipidemic, and antitumoral ones. On these bases, we offer a comprehensive overview on biological effects exerted by Citrus flavonoids via targeting SIRTs, which acted as modulator of several signaling pathways. According to the reported studies, Citrus flavonoids appear to be promising SIRT modulators in many different pathologies, a role which might be potentially evaluated in future therapies, along with encouraging the study of those SIRT members which still lack proper evidence on their support.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Targeting Autophagy, Apoptosis, and Oxidative Perturbations with Dapagliflozin Mitigates Cadmium-Induced Cognitive Dysfunction in Rats

Cognitive decline and Alzheimer-like neuropathology are common manifestations of cadmium toxicity. Thanks to its antioxidant/anti-apoptotic features, dapagliflozin has demonstrated promising neuroprotective actions. However, its effect on cadmium-induced neurotoxicity is lacking. The present work aimed to examine whether dapagliflozin could protect rats from cadmium-evoked cognitive decline. In this study, the behavioral disturbances and hippocampal biomolecular alterations were studied after receiving dapagliflozin. Herein, cadmium-induced memory/learning decline was rescued in the Morris water maze, novel object recognition task, and Y-shaped maze by dapagliflozin. Meanwhile, the hippocampal histopathological abnormalities were mitigated. The molecular mechanisms revealed that dapagliflozin lowered hippocampal expression of p-tau and Aβ42 neurotoxic proteins while augmenting acetylcholine. The cognitive enhancement was triggered by hippocampal autophagy stimulation, as indicated by decreased SQSTM-1/p62 and Beclin 1 upregulation. Meanwhile, a decrease in p-mTOR/total mTOR and an increase in p-AMPK/total AMPK ratio were observed in response to dapagliflozin, reflecting AMPK/mTOR cascade stimulation. Dapagliflozin, on the other hand, dampened the pro-apoptotic processes in the hippocampus by downregulating Bax, upregulating Bcl-2, and inactivating GSK-3β. The hippocampal oxidative insult was mitigated by dapagliflozin as seen by lipid peroxide lowering, antioxidants augmentation, and SIRT1/Nrf2/HO-1 pathway activation. In conclusion, dapagliflozin's promising neuroprotection was triggered by its pro-autophagic, anti-apoptotic, and antioxidant properties.