Intraocular administration of tetramethylpyrazine hydrochloride to rats: a direct delivery pathway for brain targeting?

Polystyrene Sulfonate Resin as an Ophthalmic Carrier for Enhanced Bioavailability of Ligustrazine Phosphate Controlled Release System

Topical ocular sustained-release drug delivery systems represent an effective strategy for the treatment of ocular diseases, for which a suitable carrier has yet to be sufficiently developed. Herein, an eye-compatible sodium polystyrene sulfonate resin (SPSR) was synthesized with a uniform particle size of about 3 μm. Ligustrazine phosphate (LP) was adsorbed to SPSR by cation exchange to form LP@SPSR. LP@SPSR suspension eye drops were further developed using the combination of Carbopol 934P and xanthan gum as suspending agents. The LP@SPSR suspension showed a sustained release in vitro, which was consistent with the observed porcine corneal penetration ex vivo. Pharmacokinetics in tear fluid of rabits indicated that LP@SPSR suspension led to prolonged ocular retention of LP and a 2-fold improved the area under the drug concentration-time curve (AUC0-t). Pharmacokinetics in the aqueous humor of rabbits showed 2.8-fold enhancement in the AUC0-t compared to LP solution. The LP@SPSR suspension exhibited no cytotoxicity to human corneal epithelial cells, nor irritation was observed in rabbit eyes. Thus, the LP@SPSR suspension has been validated as a safe and sustained release system leading to enhanced ophthalmic bioavailability for treating ocular diseases.

Design and Evaluation of Ophthalmic Thermosensitive In Situ Gel of Compound Salvia

The compound Salvia Recipe has been shown to have a relatively significant curative effect in management of cardiovascular and cerebrovascular diseases. This work aimed to prepare a thermosensitive in situ gel (ISG) delivery system that utilizes Poloxamer 407, Poloxamer 188, and hydroxypropyl methylcellulose for ocular administration of the compound Salvia recipe to treat cardiovascular and cerebrovascular diseases. The central composite design-response surface method was utilized to improve the prescription of the gel. The formulated gel was characterized and assessed in terms of stability, retention time, in vitro release, rheology, ocular irritation, pharmacokinetics studies, and tissue distribution. The gel was a liquid solution at room temperature and became semisolid at physiological temperature, prolonging its stay time in the eye. Pharmacokinetics and tissue distribution experiments indicated that thermosensitive ISG had enhanced targeting of heart and brain tissues. Additionally, it could lower drug toxicity and side effects in the lungs and kidneys. The compound Salvia ophthalmic thermosensitive ISG is a promising drug delivery system for the management of cardiovascular and cerebrovascular illnesses.

Bibliometric analysis of research progress on tetramethylpyrazine and its effects on ischemia-reperfusion injury

In recent decades, natural products have attracted worldwide attention and become one of the most important resources for pharmacological industries and medical sciences to identify novel drug candidates for disease treatment. Tetramethylpyrazine (TMP) is an alkaloid extracted from Ligusticum chuanxiong Hort., which has shown great therapeutic potential in cardiovascular and cerebrovascular diseases, liver and renal injury, as well as cancer. In this review, we analyzed 1270 papers published on the Web of Science Core Collection from 2002 to 2022 and found that TMP exerted significant protective effects on ischemia-reperfusion (I/R) injury that is the cause of pathological damages in a variety of conditions, such as ischemic stroke, myocardial infarction, acute kidney injury, and liver transplantation. TMP is limited in clinical applications to some extent due to its rapid metabolism, a short biological half-life and poor bioavailability. Obviously, the structural modification, administration methods and dosage forms of TMP need to be further investigated in order to improve its bioavailability. This review summarizes the clinical applications of TMP, elucidates its potential mechanisms in protecting I/R injury, provides strategies to improve bioavailability, which presents a comprehensive understanding of the important compound. Hopefully, the information and knowledge from this review can help researchers and physicians to better improve the applications of TMP in the clinic.

Preparation, characterisation, pharmacokinetics and distribution of esculin microspheres administered via intravitreal injection into rabbit brain

This study explored the distribution of esculin microspheres in rabbit brain tissue following intravitreal injection and investigated the possibility of direct entry of the drug into the brain through the eye, to develop a formulation with enhanced therapeutic efficacy against Parkinson's disease.Chitosan microspheres of esculin were prepared via an emulsification cross-linking method and their characteristics were evaluated, including angle of repose, bulk density, and swelling ratio. Furthermore, the pharmacokinetic parameters and brain tissue distribution in rabbits were compared among groups administered esculin eye drops, intravitreal esculin solution, and intravitreal esculin microspheres, to determine whether esculin could enter the brain through an ocular route.The results showed that the prepared esculin microspheres were spherical and had good fluidity. Notably, intravitreal administration enhanced the area under the curve (AUC) of esculin in the thalamus. Delivery through microspheres prolonged the drug retention time in both rabbit plasma and brain tissues, as well as the brain-targeting efficiency of esculin.The collective findings indicated that there may be a direct eye-brain pathway facilitating enter of esculin microspheres into brain tissue after intravitreal injection, supporting the utility of intravitreal esculin microspheres as an effective therapeutic formulation for Parkinson's disease, a long-term chronic condition.

Gypenoside XLIX protects against acute kidney injury by suppressing IGFBP7/IGF1R-mediated programmed cell death and inflammation

BACKGROUND

Acute kidney injury (AKI), characterised by excessive inflammatory cell recruitment and programmed cell death, has a high morbidity and mortality; however, effective and specific therapies for AKI are still lacking.

OBJECTIVE

This study aimed to evaluate the renoprotective effects of gypenoside XLIX (Gyp XLIX) in AKI.

METHODS

The protective effects of Gyp XLIX were tested in two AKI mouse models established using male C57BL/6 mice (aged 6-8 weeks) by a single intraperitoneal injection of cisplatin (20 mg/kg) or renal ischemia-reperfusion for 40 min. Gyp XLIX was administered intraperitoneally before cisplatin administration or renal ischemia-reperfusion. Renal function, tubular injury, renal inflammation and programmed cell death were evaluated. In addition, the renoprotective effects of Gyp XLIX were also evaluated in cisplatin- or hypoxia-treated tubular epithelial cells. The mechanisms underlying these effects were then explored using RNA sequencing.

RESULTS

In vivo, Gyp XLIX substantially suppressed the increase in serum creatinine and blood urea nitrogen levels. Moreover, tubular damage was alleviated by Gyp XLIX as shown by periodic acid-Schiff staining, electron microscopy and molecular analysis of KIM-1. Consistently, we found that Gyp XLIX suppressed renal necroptosis though the RIPK1/RIPK3/MLKL pathway. The anti-inflammatory and antinecroptotic effects were further confirmed in vitro. Mechanistically, RNA sequencing showed that Gyp XLIX markedly suppressed the levels of IGF binding protein 7 (IGFBP7). Co-immunoprecipitation and western blot analysis further showed that Gyp XLIX reduced the binding of IGFBP7 to IGF1 receptor (IGF1R). Additionally, picropodophyllin, an inhibitor of IGF1R, abrogated the therapeutic effects of Gyp XLIX on cisplatin-induced renal cell injury; this finding indicated that Gyp XLIX may function by activating IGF1R-mediated downstream signalling Additionally, we also detected the metabolic distribution of Gyp XLIX after injection; Gyp XLIX had a high concentration in the kidney and exhibited a long retention time. These findings may shed light on the application of Gyp XLIX for AKI treatment clinically.

CONCLUSION

Gyp XLIX may serve as a potential therapeutic agent for AKI treatment via IGFBP7/ IGF1R-dependent mechanisms.

Design, Characterization, and Application of a pH-Triggered In Situ Gel for Ocular Delivery of Vinpocetine

We developed a pH-triggered in situ gel (ISG) for ocular delivery of vinpocetine to achieve systemic absorption and a brain-targeting effect in rats. Carbopol acted as a gelling agent combined with hydroxypropyl methylcellulose (HPMC) as a viscosity-enhancing agent. The concentration of Carbopol (0.2%, w/v) and HPMC (1.5%, w/v) was optimized for the ISG system. The optimized formulation was evaluated for studies on release in vitro, rheology, differential scanning calorimetry, ocular irritation, residence time, and in vivo pharmacokinetics. The vinpocetine ISG stayed longer in rabbit eyes than vinpocetine ointment. In vivo pharmacokinetics showed that compared with vinpocetine ointment, vinpocetine ISG attained a peak plasma concentration and area under the curve that was 1-2 folds greater in rat plasma. The Drug Targeting Index (DTI) was 1.06 and 1.26 for vinpocetine ointment and vinpocetine ISG, respectively, after ocular administration, showing that vinpocetine ISG had better distribution in rat brain. These results revealed that a pH-triggered ISG system via ocular administration could be an alternative approach compared with traditional ophthalmic formulations.

A novel flunarizine hydrochloride-loaded organogel for intraocular drug delivery in situ: Design, physicochemical characteristics and inspection

We developed a safe and efficacious drug delivery system for treatment of brain diseases. A novel in-situ gel system was prepared using soybean oil, stearic acid and N-methyl-2-pyrrolidinone (NMP) (10:1:3, v/w/v). This system had low viscosity as a sol in vitro and turned into a solid or semi-solid gel in situ after administration. The poorly water-soluble drug flunarizine hydrochloride (FNZ) was incorporated into this "organogel" system. Organogel-FNZ was characterized by light microscopy, differential scanning calorimetry (DSC) and rheology. Drug release in vitro was investigated. The initial "burst" effect did not occur in organogel-FNZ, which is different from other gels formed in situ. Pharmacokinetic studies were undertaken in rats using gel administration (14 mg kg^-1), intravenous administration (5 mg kg^-1) and administration using drops (14 mg kg^-1). Organogel-FNZ could reduce the clearance rate and prolong the duration of action, in the plasma and brain tissues of rats. The peak serum concentration, area under the curve and absolute bioavailability of the organogel-FNZ group were higher than those of the intraocular- drops group. Organogel-FNZ is a promising drug-delivery system for treatment of brain diseases by intraocular administration.