Oral delivery of proteins and peptides: Challenges, status quo and future perspectives

Proteins and peptides (PPs) have gradually become more attractive therapeutic molecules than small molecular drugs due to their high selectivity and efficacy, but fewer side effects. Owing to the poor stability and limited permeability through gastrointestinal (GI) tract and epithelia, the therapeutic PPs are usually administered by parenteral route. Given the big demand for oral administration in clinical use, a variety of researches focused on developing new technologies to overcome GI barriers of PPs, such as enteric coating, enzyme inhibitors, permeation enhancers, nanoparticles, as well as intestinal microdevices. Some new technologies have been developed under clinical trials and even on the market. This review summarizes the history, the physiological barriers and the overcoming approaches, current clinical and preclinical technologies, and future prospects of oral delivery of PPs.

A review of existing strategies for designing long-acting parenteral formulations: Focus on underlying mechanisms, and future perspectives

The need for long-term treatments of chronic diseases has motivated the widespread development of long-acting parenteral formulations (LAPFs) with the aim of improving drug pharmacokinetics and therapeutic efficacy. LAPFs have been proven to extend the half-life of therapeutics, as well as to improve patient adherence; consequently, this enhances the outcome of therapy positively. Over past decades, considerable progress has been made in designing effective LAPFs in both preclinical and clinical settings. Here we review the latest advances of LAPFs in preclinical and clinical stages, focusing on the strategies and underlying mechanisms for achieving long acting. Existing strategies are classified into manipulation of in vivo clearance and manipulation of drug release from delivery systems, respectively. And the current challenges and prospects of each strategy are discussed. In addition, we also briefly discuss the design principles of LAPFs and provide future perspectives of the rational design of more effective LAPFs for their further clinical translation.

The effect of sex on immune responses to a homocitrullinated peptide in the DR4-transgenic mouse model of Rheumatoid Arthritis

Rheumatoid Arthritis (RA) is more common and severe in women compared to men. Both women and men with RA express autoantibodies to post-translationally modified antigens, including citrullinated and homocitrullinated proteins or peptides. These autoantibodies are strongly linked with the HLA-DR4 gene. The objective of this study was to determine sex differences in immune responses to homocitrullinated antigens. We used a humanized animal model of RA, DR4-transgenic mice and immunized them with a homocitrullinated peptide called HomoCitJED. Immune responses in these mice were measured for splenocyte proliferation by tritiated thymidine incorporation, serum autoantibody production by ELISA and cytokine levels by multiplex. We found that T cell and antibody responses to homocitrullinated antigens were similar in male and female mice. However, we found sex differences in serum cytokine profiles with female mice having higher ratio of IL-1α to IL-5, suggesting imbalances in immune regulation. This is the first study to report that immune responses to homocitrullinated antigens can be differentiated by sex.

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Splenocyte proliferation and antibody responses in DR4tg mice immunized with a homocitrullinated peptide were similar for females and males.

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The cytokine profile of homocitrullinated peptide-immunized DR4tg mice was differentiated by sex: females had a higher ratio of IL-1α to IL-5.

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Anti-homocitrullinated peptide splenocyte and antibody responses were more frequent in DR4tg than wild-type B6 mice.

Pharmacokinetic data of synthetic cathinones in female Sprague-Dawley rats

The synthetic cathinones methylone, butylone, and pentylone differ from each other through the one carbon lengthening of the α-alkyl chain: methylone (-CH3), butylone (-CH2CH3), and pentylone (-CH2CH2CH3) while 3,4-methylenedioxymethamphetamine (MDMA) differs from methylone by a single oxygen atom. Studies with MDMA, suggests that there may be male and female pharmacokinetic and pharmacodynamic differences. In the present study, we present the plasma pharmacokinetic data relative to a 20 mg/kg, subcutaneous doses of methylone, butylone and pentylone in female Sprague-Dawley rats. Briefly, plasma samples were collected via a jugular vein cannula, purified, and analyzed using a HPLC system. While we have previously reported on the consistent relationship between structure and pharmacokinetics of these synthetic cathinones in male, Sprague-Dawley rats (Grecco and Sprague, 2016), this data set suggests that there is no consistent relationship of chemical structure and pharmacokinetics of methylone, butylone and pentylone in female Sprague-Dawley rats. The findings from the present study further emphasize the need for the inclusion of female subjects in the pharmacokinetic studies of synthetic cathinones as it is very possible male-female differences may exist in rodent models.

Physiological role for leptin in the control of thermal conductance

Objective

To investigate the role played by leptin in thermoregulation, we studied the effects of physiological leptin replacement in leptin-deficient ob/ob mice on determinants of energy balance, thermogenesis and heat retention under 3 different ambient temperatures.

Methods

The effects of housing at 14 °C, 22 °C or 30 °C on core temperature (telemetry), energy expenditure (respirometry), thermal conductance, body composition, energy intake, and locomotor activity (beam breaks) were measured in ob/ob mice implanted subcutaneously with osmotic minipumps at a dose designed to deliver a physiological replacement dose of leptin or its vehicle-control.

Results

As expected, the hypothermic phenotype of ob/ob mice was partially rescued by administration of leptin at a dose that restores plasma levels into the physiological range. This effect of leptin was not due to increased energy expenditure, as cold exposure markedly and equivalently stimulated energy expenditure and induced activation of brown adipose tissue irrespective of leptin treatment. Instead, the effect of physiological leptin replacement to raise core body temperature of cold-exposed ob/ob mice was associated with reduced thermal conductance, implying a physiological role for leptin in heat conservation. Finally, both leptin- and vehicle-treated ob/ob mice failed to match energy intake to expenditure during cold exposure, resulting in weight loss.

Conclusions

The physiological effect of leptin to reduce thermal conductance contributes to maintenance of core body temperature under sub-thermoneutral conditions.

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Physiological leptin replacement partially rescues hypothermia in cold-exposed ob/ob mice.

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Leptin's normothermic effect cannot be explained by increased energy expenditure.

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This effect does not appear to be mediated by changes in physical activity.

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Leptin promotes normothermia during cold exposure by reducing thermal conductance.

Enhancement of ionizing radiation response by histamine in vitro and in vivo in human breast cancer

The radioprotective potential of histamine on healthy tissue has been previously demonstrated. The aims of this work were to investigate the combinatorial effect of histamine or its receptor ligands and gamma radiation in vitro on the radiobiological response of 2 breast cancer cell lines (MDA-MB-231 and MCF-7), to explore the potential molecular mechanisms of the radiosensitizing action and to evaluate the histamine-induced radiosensitization in vivo in a triple negative breast cancer model. Results indicate that histamine significantly increased the radiosensitivity of MDA-MB-231 and MCF-7 cells. This effect was mimicked by the H1R agonist 2-(3-(trifluoromethyl)phenyl)histamine and the H4R agonists (Clobenpropit and VUF8430) in MDA-MB-231 and MCF-7 cells, respectively. Histamine and its agonists enhanced radiation-induced oxidative DNA damage, DNA double-strand breaks, apoptosis and senescence. These effects were associated with increased production of reactive oxygen species, which correlated with the inhibition of catalase, glutathione peroxidase and superoxide dismutase activities in MDA-MB-231 cells. Histamine was able also to potentiate in vivo the anti-tumoral effect of radiation, increasing the exponential tumor doubling time. We conclude that histamine increased radiation response of breast cancer cells, suggesting that it could be used as a potential adjuvant to enhance the efficacy of radiotherapy.