Effects of Kumaizasa (Sasa senanensis) Leaf Extract on Innate Immune Regulation in HEK293 Cells and Macrophages

BACKGROUND/AIM

We investigated the effect of Kumaizasa leaf extract (KLE) on innate immunity using the HEK293 and RAW 264.7 cell lines.

MATERIALS AND METHODS

KLE, lipopolysaccharides (LPS), or KLE with LPS were added to RAW 264.7 cells. The TNF-α and IL-1β mRNA expression was then quantified. The expression of MAPKs, NFĸB, TNF-α and IL-1β proteins was also quantified. In addition, KLE was added to HEK293 cells and the IL-8 concentration was measured.

RESULTS

In RAW 264.7 cells, KLE increased the levels of TNF-α and IL-1β mRNA. By contrast, when KLE and LPS were added to RAW 264.7 cells, the increase in TNF-α and IL-1β mRNA was ameliorated. Similarly, the expression of JNK and ERK proteins was reduced. The addition of KLE to HEK293 cells induced IL-8 production.

CONCLUSION

Based on these results, a KLE-mediated mechanism may regulate immunity by suppressing the expression of JNK and ERK, which are involved in inflammatory signal transduction.

Gross primary production of dwarf bamboo, Sasa senanensis, in a mature beech forest with a substantial gap-mosaic structure

Forest understory plays an important role in the gross primary production (GPP) of some forest ecosystems. However, differences in understory GPP caused by obviously different overstory canopy structure have not been taken into consideration in previous studies, thus potentially over- or underestimating understory GPP. To estimate the understory GPP more accurately, we separated a forest into "canopy area", with closed-overstory canopy, and "gap area", with open-overstory canopy. The study was conducted in a mature deciduous forest dominated by beech and with an understory dominated by dwarf bamboo, Sasa senanensis. We measured S. senanensis GPP at the community scale (GPP_{Sasa-community}) using a static chamber system that covered the aboveground part of the plants and then upscaled it to the ecosystem scale (GPP_{Sasa-ecosystem}) by considering the proportions of canopy and gap areas within the forest. GPP_{Sasa-community} was 192 g C m^-2 year^-1 in the canopy area and 699 g C m^-2 year^-1 in the gap area. The large difference likely occurred because the photosynthetic ability and biomass of the S. senanensis community differed strongly between the two areas. The seasonal dynamics of GPP_{Sasa-community} also differed between the areas. The 10-day cumulative GPP_{Sasa-community} peaked from July to August in the gap area, whereas there was no clear peak of GPP_{Sasa-community} in the canopy area. Multiple linear regressions showed that light intensity and biomass were significant predictors of GPP_{Sasa-community} in the canopy area, whereas air temperature and biomass were significant predictors of GPP_{Sasa-community} in the gap area. GPP_{Sasa-ecosystem} during growing season in 2019 was 3.74 t C ha^-1 year^-1, which contributed between 16.37 and 19.85% of the entire forest ecosystem GPP. This study highlights the need to consider differences in overstory structure for the accurate estimation of understory GPP.

Nutrient sufficiency in beef cows grazing on a dwarf bamboo-dominated forestland pasture in Japan

The nutritional status of cows grazing on a 120-ha public alpine forestland pasture dominated by the dwarf bamboo Sasa senanensis located in central Japan was evaluated over the course of 2 years. Data were collected during grazing seasons in three periods: early (June), mid- (August) and late (late September-early October) periods. During these periods, the number of experimental Japanese Black cows varied between three and six. With the exception of the dry matter (DM) intake in 2005 and the crude protein (CP) digestibility in 2006, the DM and CP intake and digestibility were lower in the mid- and late periods than in the early period for both years (P < 0.05). Metabolizable energy intake was slightly insufficient for the requirement of the cows in the late period of 2005; in the mid- and late periods of 2006, the metabolizable energy intake was 0.4 to 0.5 times the requirement. These results suggest that the energy intake of cows grazing on forestland pasture dominated by S. senanensis would not satisfy their requirements starting in the mid-period (August) grazing, even though the pasture had abundant herbage resources during these periods.

Factors contributing to deep supercooling capability and cold survival in dwarf bamboo (Sasa senanensis) leaf blades

Wintering Sasa senanensis, dwarf bamboo, is known to employ deep supercooling as the mechanism of cold hardiness in most of its tissues from leaves to rhizomes. The breakdown of supercooling in leaf blades has been shown to proceed in a random and scattered manner with a small piece of tissue surrounded by longitudinal and transverse veins serving as the unit of freezing. The unique cold hardiness mechanism of this plant was further characterized using current year leaf blades. Cold hardiness levels (LT20: the lethal temperature at which 20% of the leaf blades are injured) seasonally increased from August (-11°C) to December (-20°C). This coincided with the increases in supercooling capability of the leaf blades as expressed by the initiation temperature of low temperature exotherms (LTE) detected in differential thermal analyses (DTA). When leaf blades were stored at -5°C for 1-14 days, there was no nucleation of the supercooled tissue units either in summer or winter. However, only summer leaf blades suffered significant injury after prolonged supercooling of the tissue units. This may be a novel type of low temperature-induced injury in supercooled state at subfreezing temperatures. When winter leaf blades were maintained at the threshold temperature (-20°C), a longer storage period (1-7 days) increased lethal freezing of the supercooled tissue units. Within a wintering shoot, the second or third leaf blade from the top was most cold hardy and leaf blades at lower positions tended to suffer more injury due to lethal freezing of the supercooled units. LTE were shifted to higher temperatures (2-5°C) after a lethal freeze-thaw cycle. The results demonstrate that the tissue unit compartmentalized with longitudinal and transverse veins serves as the unit of supercooling and temperature- and time-dependent freezing of the units is lethal both in laboratory freeze tests and in the field. To establish such supercooling in the unit, structural ice barriers such as development of sclerenchyma and biochemical mechanisms to increase the stability of supercooling are considered important. These mechanisms are discussed in regard to ecological and physiological significance in winter survival.