Mettl1 knockdown alleviates cardiac I/R injury in mice by inactivating the Mettl1-CYLD-P53 positive feedback loop.

The N7-methylguanosine (m7G) methyltransferase Mettl1 has been recently implicated in cardiac repair and fibrosis. In this study we investigated the role of Mettl1 in mouse cardiomyocytes injury and the underlying mechanisms. Cardiac ischemia/reperfusion (I/R) I/R model was established in mice by ligation of the left anterior descending coronary artery (LAD) for 45 min followed by reperfusion for 24 h. We showed the mRNA and protein levels of Mettl1 were significantly upregulated in mouse I/R hearts and H2O2-treated neonatal mouse cardiomyocytes (NMCMs). Mettl1 knockdown markedly ameliorated cardiac I/R injury, evidenced by decreased infarct size, apoptosis, and improved cardiac function. Overexpression of Mettl1 triggered cardiomyocytes apoptosis in vivo and in vitro. By performing RNA sequencing combined with m7G methylated RNA sequencing in Mettl1-overexpressing mouse hearts, we revealed that Mettl1 catalyzed m7G modification of the deubiquitinase cylindromatosis (CYLD) mRNA to increase the expression of CYLD, which enhanced the stability of P53 via abrogating its ubiquitination degradation. Vice versa, P53 served as a transcriptional factor to positively regulate Mettl1 expression during I/R injury. Knockdown of CYLD mitigated cardiomyocytes apoptosis induced by Mettl1 overexpression or oxidative stress. From the available drug-targets databases and literature, we identified 4 small molecule inhibitors of m7G modification. Sinefungin, one of the Mettl1 inhibitors exerted profound protection against cardiac I/R injury in vivo and in vitro. Collectively, this study has identified Mettl1 as a key regulator of cardiomyocyte apoptosis, and targeting the Mettl1-CYLD-P53 positive feedback circuit may represent a novel therapeutic avenue for alleviating cardiac I/R injury.

The m7G Methyltransferase Mettl1 Drives Cardiac Hypertrophy by Regulating SRSF9-Mediated Splicing of NFATc4.

Cardiac hypertrophy is a key factor driving heart failure (HF), yet its pathogenesis remains incompletely elucidated. Mettl1-catalyzed RNA N7-methylguanosine (m7G) modification has been implicated in ischemic cardiac injury and fibrosis. This study aims to elucidate the role of Mettl1 and the mechanism underlying non-ischemic cardiac hypertrophy and HF. It is found that Mettl1 is upregulated in human failing hearts and hypertrophic murine hearts following transverse aortic constriction (TAC) and Angiotensin II (Ang II) infusion. YY1 acts as a transcriptional factor for Mettl1 during cardiac hypertrophy. Mettl1 knockout alleviates cardiac hypertrophy and dysfunction upon pressure overload from TAC or Ang II stimulation. Conversely, cardiac-specific overexpression of Mettl1 results in cardiac remodeling. Mechanically, Mettl1 increases SRSF9 expression by inducing m7G modification of SRSF9 mRNA, facilitating alternative splicing and stabilization of NFATc4, thereby promoting cardiac hypertrophy. Moreover, the knockdown of SRSF9 protects against TAC- or Mettl1-induced cardiac hypertrophic phenotypes in vivo and in vitro. The study identifies Mettl1 as a crucial regulator of cardiac hypertrophy, providing a novel therapeutic target for HF.

The positive feedback loop of the NAT10/Mybbp1a/p53 axis promotes cardiomyocyte ferroptosis to exacerbate cardiac I/R injury.

Ferroptosis is a nonapoptotic form of regulated cell death that has been reported to play a central role in cardiac ischemia‒reperfusion (I/R) injury. N-acetyltransferase 10 (NAT10) contributes to cardiomyocyte apoptosis by functioning as an RNA ac4c acetyltransferase, but its role in cardiomyocyte ferroptosis during I/R injury has not been determined. This study aimed to elucidate the role of NAT10 in cardiac ferroptosis as well as the underlying mechanism. The mRNA and protein levels of NAT10 were increased in mouse hearts after I/R and in cardiomyocytes that were exposed to hypoxia/reoxygenation. P53 acted as an endogenous activator of NAT10 during I/R in a transcription-dependent manner. Cardiac overexpression of NAT10 caused cardiomyocyte ferroptosis to exacerbate I/R injury, while cardiomyocyte-specific knockout of NAT10 or pharmacological inhibition of NAT10 with Remodelin had the opposite effects. The inhibition of cardiomyocyte ferroptosis by Fer-1 exerted superior cardioprotective effects against the NAT10-induced exacerbation of post-I/R cardiac damage than the inhibition of apoptosis by emricasan. Mechanistically, NAT10 induced the ac4C modification of Mybbp1a, increasing its stability, which in turn activated p53 and subsequently repressed the transcription of the anti-ferroptotic gene SLC7A11. Moreover, knockdown of Mybbp1a partially abolished the detrimental effects of NAT10 overexpression on cardiomyocyte ferroptosis and cardiac I/R injury. Collectively, our study revealed that p53 and NAT10 interdependently cooperate to form a positive feedback loop that promotes cardiomyocyte ferroptosis to exacerbate cardiac I/R injury, suggesting that targeting the NAT10/Mybbp1a/p53 axis may be a novel approach for treating cardiac I/R.

Mettl13 protects against cardiac contractile dysfunction by negatively regulating C-Cbl-mediated ubiquitination of SERCA2a in ischemic heart failure.

Ischemic heart failure (HF) remains a leading cause of morbidity and mortality. Maintaining homeostasis of cardiac function and preventing cardiac remodeling deterioration are critical to halting HF progression. Methyltransferase-like protein 13 (Mettl13) has been shown to regulate protein translation efficiency by acting as a protein lysine methyltransferase, but its role in cardiac pathology remains unexplored. This study aims to characterize the roles and mechanisms of Mettl13 in cardiac contractile function and HF. We found that Mettl13 was downregulated in the failing hearts of mice post-myocardial infarction (MI) and in a cellular model of oxidative stress. Cardiomyocyte-specific overexpression of Mettl13 mediated by AAV9-Mettl13 attenuated cardiac contractile dysfunction and fibrosis in response to MI, while silencing of Mettl13 impaired cardiac function in normal mice. Moreover, Mettl13 overexpression abrogated the reduction in cell shortening, Ca2+ transient amplitude and SERCA2a protein levels in the cardiomyocytes of adult mice with MI. Conversely, knockdown of Mettl13 impaired the contractility of cardiomyocytes, and decreased Ca2+ transient amplitude and SERCA2a protein expression in vivo and in vitro. Mechanistically, Mettl13 impaired the stability of c-Cbl by inducing lysine methylation of c-Cbl, which in turn inhibited ubiquitination-dependent degradation of SERCA2a. Furthermore, the inhibitory effects of knocking down Mettl13 on SERCA2a protein expression and Ca2+ transients were partially rescued by silencing c-Cbl in H2O2-treated cardiomyocytes. In conclusion, our study uncovers a novel mechanism that involves the Mettl13/c-Cbl/SERCA2a axis in regulating cardiac contractile function and remodeling, and identifies Mettl13 as a novel therapeutic target for ischemic HF.

Photoacoustic imaging-guided triple-responsive nanoparticles with tumor hypoxia relief for improving chemotherapy/ photothermal/photodynamic synergistic therapy against breast cancer.

Chemo-photothermal/photodynamic synergistic therapy is a new effective cancer treatment method to overcome the limitations of single chemotherapy. However, the limited low photothermal conversion efficiency, the hypoxic tumor microenvironment, and premature leakage of the drug constrain their clinical applications. To address these challenges, an all-in-one biodegradable polydopamine-coated UiO-66 framework nanomedicine (DUPM) was developed to co-deliver the drug doxorubicin hydrochloride (DOX) and the excellent photothermal material MoOx nanoparticles (NPs). The results showed that DUPM exhibited good physicochemical stability and efficiently accumulated tumor tissues under pH-, glutathione-, and NIR-triggered drug release behaviour. Of note, the synthesized MoOx NPs endowed DUPM with self-supporting oxygen production and generated more reactive oxygen species (1O2 and·OH), besides, it induces Mo-mediated redox reaction to deplete excessive glutathione thus relieving tumor hypoxia to enhance PDT, further improving synergistic therapy. Meanwhile, DUPM showed strong absorption in the near-infrared range and high photothermal conversion efficiency at 808 nm (51.50%) to realize photoacoustic imaging-guided diagnosis and treatment of cancer. Compared with monotherapy, the in vivo anti-tumor efficacy results showed that DUMP exerted satisfactory tumor growth inhibition effects (94.43%) with good biocompatibility. This study provides a facile strategy to develop intelligent multifunctional nanoparticles with tumor hypoxia relief for improving synergistic therapy and diagnosis against breast cancer.

Exosomes secreted from cardiomyocytes suppress the sensitivity of tumor ferroptosis in ischemic heart failure.

Heart failure (HF) patients in general have a higher risk of developing cancer. Several animal studies have indicated that cardiac remodeling and HF remarkably accelerate tumor progression, highlighting a cause-and-effect relationship between these two disease entities. Targeting ferroptosis, a prevailing form of non-apoptotic cell death, has been considered a promising therapeutic strategy for human cancers. Exosomes critically contribute to proximal and distant organ-organ communications and play crucial roles in regulating diseases in a paracrine manner. However, whether exosomes control the sensitivity of cancer to ferroptosis via regulating the cardiomyocyte-tumor cell crosstalk in ischemic HF has not yet been explored. Here, we demonstrate that myocardial infarction (MI) decreased the sensitivity of cancer cells to the canonical ferroptosis activator erastin or imidazole ketone erastin in a mouse model of xenograft tumor. Post-MI plasma exosomes potently blunted the sensitivity of tumor cells to ferroptosis inducers both in vitro in mouse Lewis lung carcinoma cell line LLC and osteosarcoma cell line K7M2 and in vivo with xenograft tumorigenesis model. The expression of miR-22-3p in cardiomyocytes and plasma-exosomes was significantly upregulated in the failing hearts of mice with chronic MI and of HF patients as well. Incubation of tumor cells with the exosomes isolated from post-MI mouse plasma or overexpression of miR-22-3p alone abrogated erastin-induced ferroptotic cell death in vitro. Cardiomyocyte-enriched miR-22-3p was packaged in exosomes and transferred into tumor cells. Inhibition of cardiomyocyte-specific miR-22-3p by AAV9 sponge increased the sensitivity of cancer cells to ferroptosis. ACSL4, a pro-ferroptotic gene, was experimentally established as a target of miR-22-3p in tumor cells. Taken together, our findings uncovered for the first time that MI suppresses erastin-induced ferroptosis through releasing miR-22-3p-enriched exosomes derived from cardiomyocytes. Therefore, targeting exosome-mediated cardiomyocyte/tumor pathological communication may offer a novel approach for the ferroptosis-based antitumor therapy.

Optimization and Characterization of Low-Molecular-Weight Chitosan-Coated Baicalin mPEG-PLGA Nanoparticles for the Treatment of Cataract.

The present study was to evaluate the potential effectiveness of low-molecular-weight chitosan-coated baicalin methoxy poly(ethylene glycol)-poly(d,l-lactic-co-glycolic acid) (mPEG-PLGA) nanoparticles (BA LCH NPs) for the treatment of cataract. mPEG-PLGA NPs were optimized by the Box-Behnken design and the central composite design based on the encapsulation efficiency and drug loading. Then, the BA LCH NPs were characterized based on morphology, particle size, and zeta potentials. The analytical data of differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy depicted the drug excipient compatibility. In vitro, we evaluated cell viability, cellular uptake, potential ocular irritation, transcorneal permeability, and the precorneal retention of BA LCH NPs. In vivo, the chronic selenium cataract model was selected to assess the therapeutic effect of BA LCH NPs. The size of BA LCH NPs was within the range from 148 to 219 nm and the zeta potential was 19-25 mV. Cellular uptake results showed that the fluorescence intensity of the preparations in each group increased with time, and the fluorescence intensity of the LCH NP group was significantly higher than that of the solution group. The optimized BA LCH NPs improved precorneal residence time without causing eye irritation and also showed a sustained release of BA through the cornea for effective management of cataract. Also, fluorescence tracking on the rabbit cornea showed increased corneal retention of the LCH NPs. In addition, the results of therapeutic efficacy demonstrated that BA LCH NPs can significantly reduce the content of malondialdehyde and enhanced the activities of catalase, superoxide dismutase, and glutathione peroxidase, which was comparable to positive control and better than the BA solution group. Thus, it can be inferred that the BA LCH NPs are a promising drug delivery system for enhancing the ophthalmic administration of BA to the posterior segment of the eye and improving cataract symptoms.

[Pollution Characteristics and Health Risk of Heavy Metals in Fugitive Dust Around Zhaotong City].

In order to explore the pollution characteristics and health risks of heavy metals in fugitive dust around the urban areas of Zhaotong City, road dust and soil dust samples were collected in the Zhaoyang District of Zhaotong City in May 2019. The dust samples were suspended using a particle resuspension system to obtain PM2.5 (particulate matter with an aerodynamic diameter less than or equal to 2.5 µm). The concentrations of Ca, Al, Fe, Mg, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb in PM2.5 were quantified by ICP-MS and ICP-OES. By analyzing 10 types of heavy metals in PM2.5, the results showed that the average concentration of Mn was the highest in the soil fugitive dust, followed by Cr, Ni, Zn, Cu, Co, Pb, V, As, and Cd. The average concentration of Zn in the road fugitive dust was the highest, followed by Mn, Cu, Cr, Pb, Ni, As, Co, V, and Cd. The enrichment factor (EF) indicated that Cd was strongly enriched in the two types of fugitive dust. The EFs of Cu, Zn, and Pb in road fugitive dust showed a moderate enrichment, and they were higher than those in soil fugitive dust. Correlation and principal component analysis showed that heavy metals in the two types of fugitive dust were affected by coal burning sources. At the same time, heavy metals in soil fugitive dust were affected by agricultural activity sources, and heavy metals in road fugitive dust were affected by traffic sources. The results of the health risk assessment indicated that the carcinogenic risks of Cr, Co, Ni, As, and Cd in soil fugitive dust were higher than those in road fugitive dust. The non-carcinogenic risks of heavy metals in the two types of fugitive dust for children were higher than those for adults, and the non-carcinogenic risks of Cu, Zn, and Pb in road fugitive dust were higher than those in soil fugitive dust.

Concentrations, Source Characteristics, and Health Risk Assessment of Toxic Heavy Metals in PM2.5 in a Plateau City (Kunming) in Southwest China.

To explore the mass concentration levels and health risks of heavy metals in the air in dense traffic environments, PM2.5 samples were collected at three sites in the city of Kunming in April and October 2013, and January and May 2014. Ten heavy metals--V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd and Pb--were analyzed by ICP-MS, and the results showed PM2.5 concentrations significantly higher in spring and winter than in summer and autumn, especially for Zn and Pb. The concentration of heavy metals on working days is significantly higher, indicating that vehicle emissions are significant contributors. An enrichment factor analysis showed that Cr, Mn, Ni, Cu, Zn, As, Cd and Pb come mainly from anthropogenic sources, while V and Co may be both anthropogenic and natural. The correlation and principal component analysis (PCA) showed that Ni, Cu, Zn, Cd and Pb mainly come from vehicles emissions and metallurgical industries; Cr and Mn, from vehicles emissions and road dust; and As, mainly from coal combustion. The health risk assessment shows that the non-carcinogenic risk thresholds of the heavy metals in PM2.5 to children and adult men and women are all less than 1. The carcinogenic risk of Cr for men and women in traffic-intensive areas exceeds 10-4, reaching 1.64 × 10-4 and 1.4 × 10-4, respectively.

Abscisic Acid Regulates the Root Growth Trajectory by Reducing Auxin Transporter PIN2 Protein Levels in Arabidopsis thaliana.

The root is in direct contact with soil. Modulation of root growth in response to alterations in soil conditions is pivotal for plant adaptation. Extensive research has been conducted concerning the adjustment of root elongation and architecture in response to environmental factors. However, little is known about the modulation of the root growth trajectory, as well as its hormonal mechanism. Here we report that abscisic acid (ABA) participated in controlling root growth trajectory. The roots upon ABA treatment or from ABA-accumulation double mutant cyp707a1,3 exhibit agravitropism-like growth pattern (wavy growth trajectory). The agravitropism-like phenotype is mainly ascribed to the compromised shootward transportation of auxin since we detected a reduced fluorescence intensity of auxin reporter DR5:VENUS in the root epidermis upon exogenous ABA application or in the endogenous ABA-accumulation double mutant cyp707a1,3. We then tried to decipher the mechanism by which ABA suppressed shootward auxin transport. The membrane abundance of PIN2, a facilitator of shootward auxin transport, was significantly reduced following ABA treatment and in cyp707a1,3. Finally, we revealed that ABA reduced the membrane PIN2 intensity through suppressing the PIN2 expression rather than accelerating PIN2 degradation. Ultimately, our results suggest a pivotal role for ABA in the root growth trajectory and the hormonal interactions orchestrating this process.

Mettl14 Attenuates Cardiac Ischemia/Reperfusion Injury by Regulating Wnt1/ß-Catenin Signaling Pathway.

N6-methyladenosine (m6A) methylation in RNA is a dynamic and reversible modification regulated by methyltransferases and demethylases, which has been reported to participate in many pathological processes of various diseases, including cardiac disorders. This study was designed to investigate an m6A writer Mettl14 on cardiac ischemia-reperfusion (I/R) injury and uncover the underlying mechanism. The m6A and Mettl14 protein levels were increased in I/R hearts and neonatal mouse cardiomyocytes upon oxidative stress. Mettl14 knockout (Mettl14+/-) mice showed pronounced increases in cardiac infarct size and LDH release and aggravation in cardiac dysfunction post-I/R. Conversely, adenovirus-mediated overexpression of Mettl14 markedly reduced infarct size and apoptosis and improved cardiac function during I/R injury. Silencing of Mettl14 alone significantly caused a decrease in cell viability and an increase in LDH release and further exacerbated these effects in the presence of H2O2, while overexpression of Mettl14 ameliorated cardiomyocyte injury in vitro. Mettl14 resulted in enhanced levels of Wnt1 m6A modification and Wnt1 protein but not its transcript level. Furthermore, Mettl14 overexpression blocked I/R-induced downregulation of Wnt1 and ß-catenin proteins, whereas Mettl14+/- hearts exhibited the opposite results. Knockdown of Wnt1 abrogated Mettl14-mediated upregulation of ß-catenin and protection against injury upon H2O2. Our study demonstrates that Mettl14 attenuates cardiac I/R injury by activating Wnt/ß-catenin in an m6A-dependent manner, providing a novel therapeutic target for ischemic heart disease.

Exogenous application of abscisic acid to shoots promotes primary root cell division and elongation.

Root-derived abscisic acid (ABA) is known to regulate shoot physiology, such as stomata closure. Conversely, the basipetal regulatory effect of shoot-derived ABA is poorly understood. Herein, we report that simulation of shoot-ABA accumulation by exogenous application of ABA to shoots basipetally stimulates primary root (PR) growth. ABA applied to shoots accelerates root cell division, as evidenced by the increase in meristem size and cell number and the intensity of CYCB1;1::GFP (a mitosis marker). Root ABA content was not changed following shoot ABA application, although the ABA reporter line RAB18::GFP showed an increase in ABA in the cotyledons. Shoot-ABA application increases basipetal auxin transport by 114 %. Shoot-ABA-promoted PR growth can be abolished by attenuating basipetal auxin flux using 2,3,5-triiodobenzoic acid (TIBA, an auxin transport inhibitor), demonstrating that ABA promotes PR growth by increasing basipetal auxin transport. Root cell elongation, evaluated by the total length of the first 7 cells in the elongation zone (EZ), was increased by 56 % following shoot-ABA application. The cell walls of the root EZ were alkalinized by ABA, as exhibited by 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt staining. Higher pH promotes both PR growth and cell elongation. Thus, shoot-ABA promotes cell elongation by alkalinizing the cell wall. In light of our results, we provide a representative detailed model of the basipetal regulatory effect of ABA on PR growth.

Increasing efficacy and reducing systemic absorption of brimonidine tartrate ophthalmic gels in rabbits.

Systemic absorption of ocularly administered Brimonidine Tartrate has been reported to give rise to several side-effects. Hence, it has become crucial to develop a delivery system that could increase efficacy and reduce systemic absorption. Therefore, the present work aims to develop Brimonidine Tartrate gels with different concentrations (0.05%, 0.1%, and 0.2% w/v, respectively) using Carbopol 974 P and HPMC E4M, and compare the therapeutic efficacy and systemic absorption with that of eye drop (0.2%, w/v) by UPLC-MS/MS. The result of histological analysis did not show any morphological or structural changes after the administration of formulations. In vitro residence time studies demonstrated that the gels exhibited a better precorneal residence time as compared with the eye drop. The gels with lower concentrations of the drug (0.05% and 0.1%, w/v) could significantly decrease intraocular pressure (IOP) in both normal and water-loaded rabbits as compared to the eye drop. Finally, the values of the ratio of AUC(0→∞) in comparison to eye drop showed the gels with lower concentrations of Brimonidine Tartrate could decrease the systemic absorption. From the result, it can be concluded the 0.1% ophthalmic gel has a potential to improve therapeutic efficacy and reduce the potential toxicity caused by systemic absorption.

Mixed polyethylene glycol-modified breviscapine-loaded solid lipid nanoparticles for improved brain bioavailability: preparation, characterization, and in vivo cerebral microdialysis evaluation in adult Sprague Dawley rats.

Breviscapine is used in the treatment of ischemic cerebrovascular diseases, but it has a low bioavailability in the brain due to its poor physicochemical properties and the activity of P-glycoprotein efflux pumps located at the blood-brain barrier. In the present study, breviscapine-loaded solid lipid nanoparticles (SLN) coated with polyethylene glycol (PEG) derivatives were formulated and evaluated for their ability to enhance brain bioavailability. The SLNs were either coated with polyethylene glycol (40) (PEG-40) stearate alone (Bre-GBSLN-PS) or a mixture of PEG-40 stearate and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-PEG2000 (DSPE-PEG2000) (Bre-GBSLN-PS-DSPE) and were characterized both in vitro and in vivo. The mean particle size, polydispersity index, and entrapment efficiency for Bre-GBSLN-PS and Bre-GBSLN-PS-DSPE were 21.60 ± 0.10 and 22.60 ± 0.70 nm, 0.27 ± 0.01 and 0.26 ± 0.04, and 46.89 ± 0.73% and 47.62 ± 1.86%, respectively. The brain pharmacokinetic parameters revealed that the brain bioavailability of breviscapine from the Bre-GBSLN-PS and Bre-GBSLN-PS-DSPE was significantly enhanced (p < 0.01) with the area under concentration-time curve (AUC) of 1.59 ± 0.39 and 1.42 ± 0.58 µg h/mL of breviscapine, respectively, in comparison to 0.11 ± 0.02 µg h/mL from the commercial breviscapine injection. The ratios of the brain AUC for scutellarin in comparison with the plasma scutellarin AUC for commercial breviscapine injection, Bre-GBSLN-PS, and Bre-GBSLN-PS-DSPE were 0.66%, 2.82%, and 4.51%, respectively. These results showed that though both SLN formulations increased brain uptake of breviscapine, Bre-GBSLN-PS-DSPE which was coated with a binary combination of PEG-40 stearate and DSPE-PEG2000 had a better brain bioavailability than Bre-GBSLN-PS. Thus, the coating of SLNs with the appropriate PEG derivative combination could improve brain bioavailability of breviscapine and can be a promising tool for brain drug delivery.

Comparison of systemic absorption between ofloxacin ophthalmic in situ gels and ofloxacin conventional ophthalmic solutions administration to rabbit eyes by HPLC-MS/MS.

In recent years, many pharmaceutical scientists have focused on developing the in situ gel-forming systems to overcome the poor bioavailability and therapeutic response exhibited by conventional ophthalmic solutions due to rapid pre-corneal elimination of the drug. The present work was to compare the systemic absorptions of ophthalmic ofloxacin in situ gel with the conventional ofloxacin eye drop after topical instillation to rabbit eyes by HPLC-MS/MS method and also determine the relative contribution of the nasal and the conjunctival mucosae to systemic ofloxacin absorption following topical instillation. The systemic AUC, Cmax, Tmax and Ke for ophthalmic in situ gel and ophthalmic solution after ocular instillation were 202.63±118.85 and 202.25±57.74 ng mL(-1) h, 54.22±28.31 and 48.4±25.97 ng mL(-1), 1.08±0.20 and 1.25±0.88 h, 0.0576±0.0207 and 0.0388±0.0248, respectively. And the values for the ratios of the AUC of anterior chamber of rabbit eye to blood plasma, AUCac/AUCpl, for ofloxacin conventional eye drop and in situ gel were 0.25 and 0.52, respectively. Statistic results showed that there was no significant difference in systemic absorption between the test groups and the reference groups (P>0.05) as both formulations have an AUCsa/AUCpl of 0.35. Therefore, the ophthalmic in situ gel may not decrease the drugs systemic absorption when administered in an equivalent dose as ophthalmic solutions into the rabbit eyes.